Pseudomonas
Overview
 
Pseudomonas is a genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of gammaproteobacteria
Gammaproteobacteria
Gammaproteobacteria is a class of several medically, ecologically and scientifically important groups of bacteria, such as the Enterobacteriaceae , Vibrionaceae and Pseudomonadaceae. An exceeding number of important pathogens belongs to this class, e.g...

, belonging to the family Pseudomonadaceae
Pseudomonadaceae
The Pseudomonadaceae is a family of bacteria that includes the genera Azomonas, Azomonotrichon, Azorhizophilus, Azotobacter, Cellvibrio, Mesophilobacter, Pseudomonas , Rhizobacter, Rugamonas, and Serpens...

 containing 191 validly described species.

Recently, 16S rRNA
16S ribosomal RNA
16S ribosomal RNA is a component of the 30S subunit of prokaryotic ribosomes. It is approximately 1.5kb in length...

 sequence analysis has redefined the taxonomy of many bacterial species. As a result, the genus Pseudomonas includes strains formerly classified in the genera Chryseomonas and Flavimonas. Other strains previously classified in the genus Pseudomonas are now classified in the genera Burkholderia
Burkholderia
Burkholderia is a genus of proteobacteria probably best known for its pathogenic members:Burkholderia mallei, responsible for glanders, a disease that occurs mostly in horses and related animals;...

 and Ralstonia
Ralstonia
Ralstonia is a genus of proteobacteria, previously included in the genus Pseudomonas. It is named after the American bacteriologist E. Ralston.-Genomics:* *...

.
Like most bacteria genera the pseudomonad last common ancestor lived hundreds of million years ago, however they were classified by humans at the end of the 19th century.
Because of their widespread occurrence in water and in plant seeds such as dicots, the pseudomonads were observed early in the history of microbiology
Microbiology
Microbiology is the study of microorganisms, which are defined as any microscopic organism that comprises either a single cell , cell clusters or no cell at all . This includes eukaryotes, such as fungi and protists, and prokaryotes...

.
Encyclopedia
Pseudomonas is a genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of gammaproteobacteria
Gammaproteobacteria
Gammaproteobacteria is a class of several medically, ecologically and scientifically important groups of bacteria, such as the Enterobacteriaceae , Vibrionaceae and Pseudomonadaceae. An exceeding number of important pathogens belongs to this class, e.g...

, belonging to the family Pseudomonadaceae
Pseudomonadaceae
The Pseudomonadaceae is a family of bacteria that includes the genera Azomonas, Azomonotrichon, Azorhizophilus, Azotobacter, Cellvibrio, Mesophilobacter, Pseudomonas , Rhizobacter, Rugamonas, and Serpens...

 containing 191 validly described species.

Recently, 16S rRNA
16S ribosomal RNA
16S ribosomal RNA is a component of the 30S subunit of prokaryotic ribosomes. It is approximately 1.5kb in length...

 sequence analysis has redefined the taxonomy of many bacterial species. As a result, the genus Pseudomonas includes strains formerly classified in the genera Chryseomonas and Flavimonas. Other strains previously classified in the genus Pseudomonas are now classified in the genera Burkholderia
Burkholderia
Burkholderia is a genus of proteobacteria probably best known for its pathogenic members:Burkholderia mallei, responsible for glanders, a disease that occurs mostly in horses and related animals;...

 and Ralstonia
Ralstonia
Ralstonia is a genus of proteobacteria, previously included in the genus Pseudomonas. It is named after the American bacteriologist E. Ralston.-Genomics:* *...

.

Classification History

Like most bacteria genera the pseudomonad last common ancestor lived hundreds of million years ago, however they were classified by humans at the end of the 19th century.
Because of their widespread occurrence in water and in plant seeds such as dicots, the pseudomonads were observed early in the history of microbiology
Microbiology
Microbiology is the study of microorganisms, which are defined as any microscopic organism that comprises either a single cell , cell clusters or no cell at all . This includes eukaryotes, such as fungi and protists, and prokaryotes...

. The generic name Pseudomonas created for these organisms was defined in rather vague terms by Walter Migula
Walter Migula
Walter Emil Friedrich August Migula was a German botanist, who published many articles on the subjects of cryptogamic botany, bacteriology, and plant physiology...

 in 1894 and 1900 as a genus of Gram-negative
Gram-negative
Gram-negative bacteria are bacteria that do not retain crystal violet dye in the Gram staining protocol. In a Gram stain test, a counterstain is added after the crystal violet, coloring all Gram-negative bacteria with a red or pink color...

, rod-shaped and polar-flagella bacteria with some sporulating species, the latter statement was later proved incorrect and was due to refractive granules of reserve materials. Despite the vague description, the type species, Pseudomonas pyocyanea (basonym of Pseudomonas aeruginosa
Pseudomonas aeruginosa
Pseudomonas aeruginosa is a common bacterium that can cause disease in animals, including humans. It is found in soil, water, skin flora, and most man-made environments throughout the world. It thrives not only in normal atmospheres, but also in hypoxic atmospheres, and has, thus, colonized many...

), proved the best descriptor.

Additionally, the etymology of the name was not provided and first appeared in the 7th edition of Bergey's manual (=top authority in bacterial nomeclature) as Greek
Ancient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...

  pseudes (ψευδες) "false" and -monas
-monas
The suffix -monas is used in microbiology for many genera and is intended to mean "unicellular organism".-Meaning:The suffix -monas is used in microbiology for many genera in a similar way to -bacter, -bacillus, -coccus or -spirillum...

 (μονάς / μονάδα) "a single unit", which can mean false unit, but there is also the possibility that Migula intended it as false Monas, a nanoflagellate protist. Subsequently, the term "monad" was used in the early history of microbiology to denote single-celled organisms.
Soon afterwards, species matching Migula's description were isolated from many natural niches and many were originally assigned to the genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

.

New methodology and the inclusion of approaches based on the studies of conservative macromolecules have reclassified many strains.

Pseudomonas aeruginosa
Pseudomonas aeruginosa
Pseudomonas aeruginosa is a common bacterium that can cause disease in animals, including humans. It is found in soil, water, skin flora, and most man-made environments throughout the world. It thrives not only in normal atmospheres, but also in hypoxic atmospheres, and has, thus, colonized many...

 is increasingly recognized as an emerging opportunistic pathogen of clinical relevance. Several different epidemiological studies indicate antibiotic resistance
Antibiotic resistance
Antibiotic resistance is a type of drug resistance where a microorganism is able to survive exposure to an antibiotic. While a spontaneous or induced genetic mutation in bacteria may confer resistance to antimicrobial drugs, genes that confer resistance can be transferred between bacteria in a...

 is increasing in clinical isolates.

In the year 2000, the complete genome sequence of a Pseudomonas species was determined; more recently, the sequence of other strains have been determined, including P. aeruginosa strains PAO1 (2000), P. putida KT2440 (2002), P. fluorescens Pf-5 (2005), P. syringae pathovar tomato DC3000 (2003), P. syringae pathovar syringae B728a (2005), P. syringae pathovar phaseolica 1448A (2005), P. fluorescens PfO-1 and P. entomophila L48.

An article published in the journal Scientific American
Scientific American
Scientific American is a popular science magazine. It is notable for its long history of presenting science monthly to an educated but not necessarily scientific public, through its careful attention to the clarity of its text as well as the quality of its specially commissioned color graphics...

 in 2008 showed Pseudomonas may be the most common nucleator of ice crystals in clouds, thereby being of utmost importance to the formation of snow and rain around the world.

Characteristics

Members of the genus display the following defining characteristics:
  • Rod shaped
  • Gram-negative
    Gram-negative
    Gram-negative bacteria are bacteria that do not retain crystal violet dye in the Gram staining protocol. In a Gram stain test, a counterstain is added after the crystal violet, coloring all Gram-negative bacteria with a red or pink color...

  • One or more polar flagella, providing motility
    Motility
    Motility is a biological term which refers to the ability to move spontaneously and actively, consuming energy in the process. Most animals are motile but the term applies to single-celled and simple multicellular organisms, as well as to some mechanisms of fluid flow in multicellular organs, in...

  • Aerobic
    Aerobic organism
    An aerobic organism or aerobe is an organism that can survive and grow in an oxygenated environment.Faculitative anaerobes grow and survive in an oxygenated environment and so do aerotolerant anaerobes.-Glucose:...

  • Non–spore forming
  • positive catalase
    Catalase
    Catalase is a common enzyme found in nearly all living organisms that are exposed to oxygen, where it catalyzes the decomposition of hydrogen peroxide to water and oxygen...

     test
  • positive oxidase test.

Other characteristics which tend to be associated with Pseudomonas species (with some exceptions) include secretion of pyoverdine
Pyoverdine
Pyoverdine is a fluorescent siderophore produced by the Gram negative bacterium Pseudomonas aeruginosa.In Pseudomonas aeruginosa PAO1 there are 14 pvd genes involed in the synthesis of the pyoveridine....

, a fluorescent
Fluorescence
Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation of a different wavelength. It is a form of luminescence. In most cases, emitted light has a longer wavelength, and therefore lower energy, than the absorbed radiation...

 yellow-green siderophore
Siderophore
Siderophores are small, high-affinity iron chelating compounds secreted by grasses and microorganisms such as bacteria and fungi...

 under iron-limiting conditions. Certain Pseudomonas species may also produce additional types of siderophore, such as pyocyanin by Pseudomonas aeruginosa
Pseudomonas aeruginosa
Pseudomonas aeruginosa is a common bacterium that can cause disease in animals, including humans. It is found in soil, water, skin flora, and most man-made environments throughout the world. It thrives not only in normal atmospheres, but also in hypoxic atmospheres, and has, thus, colonized many...

 and thioquinolobactin by Pseudomonas fluorescens
Pseudomonas fluorescens
Pseudomonas fluorescens is a common Gram-negative, rod-shaped bacterium. It belongs to the Pseudomonas genus; 16S rRNA analysis has placed P. fluorescens in the P. fluorescens group within the genus, to which it lends its name....

,. Pseudomonas species also typically give a positive result to the oxidase test
Oxidase test
The oxidase test is a test used in microbiology to determine if a bacterium produces certain cytochrome c oxidases. It uses disks impregnated with a reagent such as N,N,N′,N′-tetramethyl-p-phenylenediamine or N,N-Dimethyl-p-phenylenediamine , which is also a redox indicator...

, the absence of gas formation from glucose, glucose is oxidised in oxidation/fermentation test using Hugh and Leifson O/F test, beta hemolytic (on blood agar), indole
Indole test
The indole test is a biochemical test performed on bacterial species to determine the ability of the organism to split indole from the amino acid tryptophan...

 negative, methyl red
Methyl red
Methyl red, also called C.I. Acid Red 2, is an indicator dye that turns red in acidic solutions. It is an azo dye, and is a dark red crystalline powder....

 negative, Voges–Proskauer test negative, and citrate
Citrate test
- Principle :The citrate test detects the ability of an organism to use citrate as the sole source of carbon and energy. Bacteria are inoculated on a medium containing sodium citrate and a pH indicator such as bromothymol blue. The medium also contains inorganic ammonium salts, which are utilized...

 positive.

The members of the genus demonstrate a great deal of metabolic
Metabolism
Metabolism is the set of chemical reactions that happen in the cells of living organisms to sustain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Metabolism is usually divided into two categories...

 diversity, and consequently are able to colonise a wide range of niches. Their ease of culture in vitro
In vitro
In vitro refers to studies in experimental biology that are conducted using components of an organism that have been isolated from their usual biological context in order to permit a more detailed or more convenient analysis than can be done with whole organisms. Colloquially, these experiments...

 and availability of an increasing number of Pseudomonas strain genome
Genome
In modern molecular biology and genetics, the genome is the entirety of an organism's hereditary information. It is encoded either in DNA or, for many types of virus, in RNA. The genome includes both the genes and the non-coding sequences of the DNA/RNA....

 sequences has made the genus an excellent focus for scientific research; the best studied species include P. aeruginosa in its role as an opportunistic human pathogen, the plant pathogen P. syringae
Pseudomonas syringae
Pseudomonas syringae is a rod shaped, Gram-negative bacterium with polar flagella. It is a plant pathogen which can infect a wide range of plant species, and exists as over 50 different pathovars, all of which are available to legitimate researches via international culture collections such as the...

, the soil bacterium P. putida
Pseudomonas putida
Pseudomonas putida is a gram-negative rod-shaped saprotrophic soil bacterium. Based on 16S rRNA analysis, P. putida has been placed in the P. putida group, to which it lends its name....

, and the plant growth promoting P. fluorescens.

Biofilm formation

All species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 and strains of Pseudomonas are Gram-negative
Gram-negative
Gram-negative bacteria are bacteria that do not retain crystal violet dye in the Gram staining protocol. In a Gram stain test, a counterstain is added after the crystal violet, coloring all Gram-negative bacteria with a red or pink color...

 rods, and have historically been classified as strict aerobes
Aerobic organism
An aerobic organism or aerobe is an organism that can survive and grow in an oxygenated environment.Faculitative anaerobes grow and survive in an oxygenated environment and so do aerotolerant anaerobes.-Glucose:...

. Exceptions to this classification have recently been discovered in Pseudomonas biofilms. A significant number of cells can produce exopolysaccharides known as biofilms. Secretion of exopolysaccharide
Exopolysaccharide
Exopolysaccharides are high-molecular-weight polymers that are composed of sugar residues and are secreted by a microorganism into the surrounding environment. Microorganisms synthesize a wide spectrum of multifunctional polysaccharides including intracellular polysaccharides, structural...

 such as alginate, makes it difficult for pseudomonads to be phagocytosed by mammalian white blood cells. Exopolysaccharide production also contributes to surface-colonising biofilm
Biofilm
A biofilm is an aggregate of microorganisms in which cells adhere to each other on a surface. These adherent cells are frequently embedded within a self-produced matrix of extracellular polymeric substance...

s which are difficult to remove from food preparation surfaces. Growth of pseudomonads on spoiling foods can generate a "fruity" odor.

Pseudomonas have the ability to metabolise a variety of diverse nutrients. Combined with the ability to form biofilms, they are thus able to survive in a variety of unexpected places. For example, they have been found in areas where pharmaceuticals are prepared. A simple carbon source, such as soap
Soap
In chemistry, soap is a salt of a fatty acid.IUPAC. "" Compendium of Chemical Terminology, 2nd ed. . Compiled by A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford . XML on-line corrected version: created by M. Nic, J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN...

 residue or cap liner-adhesives is a suitable place for them to thrive. Other unlikely places where they have been found include antiseptic
Antiseptic
Antiseptics are antimicrobial substances that are applied to living tissue/skin to reduce the possibility of infection, sepsis, or putrefaction...

s, such as quaternary ammonium
Ammonium
The ammonium cation is a positively charged polyatomic cation with the chemical formula NH. It is formed by the protonation of ammonia...

 compounds, and bottled
Bottled water
Bottled water is drinking water packaged in plastic or glass water bottles. Bottled water may be carbonated or not...

 mineral water
Mineral water
Mineral water is water containing minerals or other dissolved substances that alter its taste or give it therapeutic value, generally obtained from a naturally occurring mineral spring or source. Dissolved substances in the water may include various salts and sulfur compounds...

.

Antibiotic resistance

Being Gram-negative bacteria, most Pseudomonas spp. are naturally resistant to penicillin
Penicillin
Penicillin is a group of antibiotics derived from Penicillium fungi. They include penicillin G, procaine penicillin, benzathine penicillin, and penicillin V....

 and the majority of related beta-lactam
Beta-lactam
A β-lactam ring, is a four-membered lactam. It is named as such, because the nitrogen atom is attached to the β-carbon relative to the carbonyl...

 antibiotics, but a number are sensitive to piperacillin
Piperacillin
Piperacillin is an extended spectrum beta-lactam antibiotic of the ureidopenicillin class.It is normally used together with a beta-lactamase inhibitor such as tazobactam. The combination drug piperacillin/tazobactam is commercially available as e.g. Tazocin, Zosyn, Brodactam, Piptaz and as Trezora...

, imipenem
Imipenem
Imipenem is an intravenous β-lactam antibiotic developed in 1980. It has an extremely broad spectrum of activity.Imipenem belongs to the subgroup of carbapenems. It is derived from a compound called thienamycin, which is produced by the bacterium Streptomyces cattleya...

, ticarcillin
Ticarcillin
Ticarcillin is a carboxypenicillin. It is almost invariably sold and used in combination with clavulanate as Timentin. Because it is a penicillin, it also falls within the larger class of beta-lactam antibiotics. Its main clinical use is as an injectable antibiotic for the treatment of...

, tobramycin, or ciprofloxacin
Ciprofloxacin
Ciprofloxacin is a synthetic chemotherapeutic antibiotic of the fluoroquinolone drug class.It is a second-generation fluoroquinolone antibacterial. It kills bacteria by interfering with the enzymes that cause DNA to rewind after being copied, which stops synthesis of DNA and of...

.

This ability to thrive in harsh conditions is a result of their hardy cell wall
Cell wall
The cell wall is the tough, usually flexible but sometimes fairly rigid layer that surrounds some types of cells. It is located outside the cell membrane and provides these cells with structural support and protection, and also acts as a filtering mechanism. A major function of the cell wall is to...

 that contains porin
Porin (protein)
Porins are beta barrel proteins that cross a cellular membrane and act as a pore through which molecules can diffuse. Unlike other membrane transport proteins, porins are large enough to allow passive diffusion, i.e., they act as channels that are specific to different types of molecules...

s. Their resistance to most antibiotics is attributed to efflux pumps
Efflux (microbiology)
Active efflux is a mechanism responsible for extrusion of toxic substances and antibiotics outside the cell; this is considered to be a vital part of xenobiotic metabolism...

, which pump out some antibiotics before the antibiotics are able to act.

Pseudomonas aeruginosa is a highly relevant opportunistic human pathogen. One of the most worrying characteristics of P. aeruginosa is its low antibiotic
Antibiotic
An antibacterial is a compound or substance that kills or slows down the growth of bacteria.The term is often used synonymously with the term antibiotic; today, however, with increased knowledge of the causative agents of various infectious diseases, antibiotic has come to denote a broader range of...

 susceptibility. This low susceptibility is attributable to a concerted action of multidrug efflux pumps with chromosomally-encoded antibiotic resistance
Antibiotic resistance
Antibiotic resistance is a type of drug resistance where a microorganism is able to survive exposure to an antibiotic. While a spontaneous or induced genetic mutation in bacteria may confer resistance to antimicrobial drugs, genes that confer resistance can be transferred between bacteria in a...

 genes (e.g. mexAB-oprM, mexXY, etc.,) and the low permeability of the bacterial cellular envelopes. Besides intrinsic resistance, P. aeruginosa easily develops acquired resistance either by mutation
Mutation
In molecular biology and genetics, mutations are changes in a genomic sequence: the DNA sequence of a cell's genome or the DNA or RNA sequence of a virus. They can be defined as sudden and spontaneous changes in the cell. Mutations are caused by radiation, viruses, transposons and mutagenic...

 in chromosomally-encoded genes, or by the horizontal gene transfer
Horizontal gene transfer
Horizontal gene transfer , also lateral gene transfer , is any process in which an organism incorporates genetic material from another organism without being the offspring of that organism...

 of antibiotic resistance determinants. Development of multidrug resistance
Multidrug resistance
Multiple drug resistance or Multidrug resistance is a condition enabling a disease-causing organism to resist distinct drugs or chemicals of a wide variety of structure and function targeted at eradicating the organism...

 by P. aeruginosa isolates requires several different genetic events that include acquisition of different mutations and/or horizontal transfer of antibiotic resistance genes. Hypermutation favours the selection of mutation-driven antibiotic resistance in P. aeruginosa strains producing chronic infections, whereas the clustering of several different antibiotic resistance genes in integron
Integron
An integron is a two component gene capture and dissemination system, initially discovered in relation to antibiotic resistance, and which is found in plasmids, chromosomes and transposons...

s favours the concerted acquisition of antibiotic resistance determinants. Some recent studies have shown phenotypic resistance associated to biofilm
Biofilm
A biofilm is an aggregate of microorganisms in which cells adhere to each other on a surface. These adherent cells are frequently embedded within a self-produced matrix of extracellular polymeric substance...

 formation or to the emergence of small-colony-variants may be important in the response of P. aeruginosa populations to antibiotic
Antibiotic
An antibacterial is a compound or substance that kills or slows down the growth of bacteria.The term is often used synonymously with the term antibiotic; today, however, with increased knowledge of the causative agents of various infectious diseases, antibiotic has come to denote a broader range of...

 treatment.

Taxonomy

The studies on the taxonomy
Taxonomy
Taxonomy is the science of identifying and naming species, and arranging them into a classification. The field of taxonomy, sometimes referred to as "biological taxonomy", revolves around the description and use of taxonomic units, known as taxa...

 of this complicated genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 groped their way in the dark while following the classical procedures developed for the description and identification of the organism
Organism
In biology, an organism is any contiguous living system . In at least some form, all organisms are capable of response to stimuli, reproduction, growth and development, and maintenance of homoeostasis as a stable whole.An organism may either be unicellular or, as in the case of humans, comprise...

s involved in sanitary bacteriology
Bacteriology
Bacteriology is the study of bacteria. This subdivision of microbiology involves the identification, classification, and characterization of bacterial species...

 during the first decades of the twentieth century. This situation sharply changed with the proposal to introduce as the central criterion the similarities in the composition and sequences of macromolecular
Macromolecule
A macromolecule is a very large molecule commonly created by some form of polymerization. In biochemistry, the term is applied to the four conventional biopolymers , as well as non-polymeric molecules with large molecular mass such as macrocycles...

s components of the ribosomal RNA
Ribosomal RNA
Ribosomal ribonucleic acid is the RNA component of the ribosome, the enzyme that is the site of protein synthesis in all living cells. Ribosomal RNA provides a mechanism for decoding mRNA into amino acids and interacts with tRNAs during translation by providing peptidyl transferase activity...

. The new methodology clearly showed the genus
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 Pseudomonas, as classically defined, consisted in fact of a conglomerate of genera
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 that could clearly be separated into five so-called rRNA homology
Homology (chemistry)
In chemistry, homology refers to the appearance of homologues. A homologue is a compound belonging to a series of compounds differing from each other by a repeating unit, such as a methylene group, a peptide residue, etcetera....

 groups. Moreover, the taxonomic studies suggested an approach that might proved useful in taxonomic studies of all other prokaryotic groups. A few decades after the proposal of the new genus Pseudomonas by Migula in 1894, the accumulation of species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 names assigned to the genus reached alarming proportions. At present, the number of species in the current list has contracted more than 90%. In fact, this approximated reduction may be even more dramatic if one considers the present list contains many new names, i.e., relatively few names of the original list survived in the process. The new methodology and the inclusion of approaches based on the studies of conservative macromolecules other than rRNA components, constitutes an effective prescription that helped to reduce Pseudomonas nomenclatural hypertrophy to a manageable size.

Animal pathogens

Infectious species include P. aeruginosa
Pseudomonas aeruginosa
Pseudomonas aeruginosa is a common bacterium that can cause disease in animals, including humans. It is found in soil, water, skin flora, and most man-made environments throughout the world. It thrives not only in normal atmospheres, but also in hypoxic atmospheres, and has, thus, colonized many...

, P. oryzihabitans
Pseudomonas oryzihabitans
Pseudomonas oryzihabitans, also known as Flavimonas orzyhabitans, is a nonfermenting yellow-pigmented, gram-negative, rod-shaped bacterium that can cause septicemia , peritonitis, endophthalmitis, and bacteremia. It is an opportunistic pathogen of humans and warm-blooded animals that is commonly...

, and P. plecoglossicida
Pseudomonas plecoglossicida
Pseudomonas plecoglossicida is a non-fluorescent, Gram-negative, rod-shaped, motile bacterium that causes hemorrhagic ascites in the ayu fish , from which it derives its name. Based on 16S rRNA analysis, P. plecoglossicida has been placed in the P. putida group....

. P. aeruginosa flourishes in hospital environments, and is a particular problem in this environment since it is the second most common infection in hospitalized patients(nosocomial infections). This pathogenesis may in part be due to the proteins secreted by P. aeruginosa. The bacterium possesses a wide range of secretion
Secretion
Secretion is the process of elaborating, releasing, and oozing chemicals, or a secreted chemical substance from a cell or gland. In contrast to excretion, the substance may have a certain function, rather than being a waste product...

 systems, which export numerous proteins relevant to the pathogenesis of clinical strains.

Plant pathogens

P. syringae
Pseudomonas syringae
Pseudomonas syringae is a rod shaped, Gram-negative bacterium with polar flagella. It is a plant pathogen which can infect a wide range of plant species, and exists as over 50 different pathovars, all of which are available to legitimate researches via international culture collections such as the...

 is a prolific plant pathogen. It exists as over 50 different pathovar
Pathovar
A pathovar is a bacterial strain or set of strains with the same or similar characteristics, that is differentiated at infrasubspecific level from other strains of the same species or subspecies on the basis of distinctive pathogenicity to one or more plant hosts.Pathovars are named as a ternary or...

s, many of which demonstrate a high degree of host plant specificity. There are numerous other Pseudomonas species that can act as plant pathogens, notably all of the other members of the P. syringae subgroup, but P. syringae is the most widespread and best studied.

Although not strictly a plant pathogen, P. tolaasii
Pseudomonas tolaasii
Pseudomonas tolaasii is a species of Gram-negative soil bacteria that is the causal agent of bacterial blotch on cultivated mushrooms . It is known to produce a toxin, called tolaasin, which is responsible for the brown blotches associated with the disease. It also demonstrates hemolytic activity,...

 can be a major agricultural problem, as it can cause bacterial blotch of cultivated mushrooms. Similarly, P. agarici
Pseudomonas agarici
Pseudomonas agarici is a Gram-negative soil bacterium that causes drippy gill in mushrooms . It was first isolated in New Zealand. P. agarici couldn't be grouped based on 16S rRNA analysis, so it is designated incertae sedis in the genus Pseudomonas....

 can cause drippy gill in cultivated mushrooms.

Use as biocontrol agents

Since the mid 1980s, certain members of the Pseudomonas genus have been applied to cereal seeds or applied directly to soils as a way of preventing the growth or establishment of crop pathogens. This practice is generically referred to as biocontrol
BioControl
BioControl is a peer-reviewed scientific journal published by Springer Science+Business Media covering all aspects of basic and applied research in biological control of invertebrate, vertebrate, and weed pests, and plant diseases. The journal was established in 1956 as Entomophaga and published by...

. The biocontrol properties of P. fluorescens
Pseudomonas fluorescens
Pseudomonas fluorescens is a common Gram-negative, rod-shaped bacterium. It belongs to the Pseudomonas genus; 16S rRNA analysis has placed P. fluorescens in the P. fluorescens group within the genus, to which it lends its name....

 strains (CHA0 or Pf-5 for example) are currently best understood, although it is not clear exactly how the plant growth-promoting properties of P. fluorescens are achieved. Theories include: that the bacteria might induce systemic resistance in the host plant, so it can better resist attack by a true pathogen; the bacteria might out compete other (pathogenic) soil microbes, e.g. by siderophore
Siderophore
Siderophores are small, high-affinity iron chelating compounds secreted by grasses and microorganisms such as bacteria and fungi...

s giving a competitive advantage at scavenging for iron; the bacteria might produce compounds antagonistic to other soil microbes, such as phenazine
Phenazine
Phenazine , also called azophenylene, dibenzo-p-diazine, dibenzopyrazine, and acridizine, is a dibenzo annulated pyrazine and the parent substance of many dyestuffs, such as the eurhodines, toluylene red, indulines and safranines.-Synthesis:A classic method for the synthesis of phenazine is the...

-type antibiotics or hydrogen cyanide. There is experimental evidence to support all of these theories.

Other notable Pseudomonas species with biocontrol properties include P. chlororaphis
Pseudomonas chlororaphis
Pseudomonas chlororaphis is a bacterium used as a soil inoculant in agriculture and horticulture. It can act as a biocontrol agent against certain fungal plant pathogens via production of phenazine type antibiotics. Based on 16S rRNA analysis, P. chlororaphis has been placed in the P. chlororaphis...

, which produces a phenazine
Phenazine
Phenazine , also called azophenylene, dibenzo-p-diazine, dibenzopyrazine, and acridizine, is a dibenzo annulated pyrazine and the parent substance of many dyestuffs, such as the eurhodines, toluylene red, indulines and safranines.-Synthesis:A classic method for the synthesis of phenazine is the...

-type antibiotic
Antibiotic
An antibacterial is a compound or substance that kills or slows down the growth of bacteria.The term is often used synonymously with the term antibiotic; today, however, with increased knowledge of the causative agents of various infectious diseases, antibiotic has come to denote a broader range of...

 active agent against certain fungal
Fungus
A fungus is a member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds , as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from plants, animals, and bacteria...

 plant pathogens, and the closely related species P. aurantiaca
Pseudomonas aurantiaca
Pseudomonas aurantiaca is an orange Gram-negative soil bacterium, originally isolated from the rhizosphere soil of potatoes. It produces di-2,4-diacetylfluoroglucylmethan, which is antibiotically active against Gram-positive organisms. It has shown potential for use as a biocontrol agent against...

 which produces di-2,4-diacetylfluoroglucylmethane, a compound antibiotic
Antibiotic
An antibacterial is a compound or substance that kills or slows down the growth of bacteria.The term is often used synonymously with the term antibiotic; today, however, with increased knowledge of the causative agents of various infectious diseases, antibiotic has come to denote a broader range of...

ally active against Gram-positive
Gram-positive
Gram-positive bacteria are those that are stained dark blue or violet by Gram staining. This is in contrast to Gram-negative bacteria, which cannot retain the crystal violet stain, instead taking up the counterstain and appearing red or pink...

 organisms.

Use as bioremediation agents

Some members of the genus Pseudomonas are able to metabolise chemical pollutants in the environment, and as a result can be used for bioremediation
Bioremediation
Bioremediation is the use of microorganism metabolism to remove pollutants. Technologies can be generally classified as in situ or ex situ. In situ bioremediation involves treating the contaminated material at the site, while ex situ involves the removal of the contaminated material to be treated...

. Notable species demonstrated as suitable for use as bioremediation agents include:
  • P. alcaligenes
    Pseudomonas alcaligenes
    Pseudomonas alcaligenes is a Gram-negative aerobic bacterium used as a soil inoculant for bioremediation purposes, as it can degrade polycyclic aromatic hydrocarbons. It can be a human pathogen but occurrences are very rare. Based on 16S rRNA analysis, P. alcaligenes has been placed in the P....

    , which can degrade polycyclic aromatic hydrocarbon
    Polycyclic aromatic hydrocarbon
    Polycyclic aromatic hydrocarbons , also known as poly-aromatic hydrocarbons or polynuclear aromatic hydrocarbons, are potent atmospheric pollutants that consist of fused aromatic rings and do not contain heteroatoms or carry substituents. Naphthalene is the simplest example of a PAH...

    s.
  • P. mendocina
    Pseudomonas mendocina
    Pseudomonas mendocina is a Gram-negative environmental bacterium that can cause opportunistic nosocomial infections, such as infective endocarditis and spondylodiscitis, although cases are very rare. It has potential use in bioremediation as it is able to degrade toluene. Based on 16S rRNA...

    , which is able to degrade toluene
    Toluene
    Toluene, formerly known as toluol, is a clear, water-insoluble liquid with the typical smell of paint thinners. It is a mono-substituted benzene derivative, i.e., one in which a single hydrogen atom from the benzene molecule has been replaced by a univalent group, in this case CH3.It is an aromatic...

    .
  • P. pseudoalcaligenes
    Pseudomonas pseudoalcaligenes
    Pseudomonas pseudoalcaligenes is an aerobic, Gram negative soil bacterium that was first isolated from swimming pool water. It is able to use cyanide as a nitrogen source, and as a result it may be used for bioremediation. Based on 16S rRNA analysis, P. pseudoalcaligenes has been placed in the P....

     is able to use cyanide
    Cyanide
    A cyanide is a chemical compound that contains the cyano group, -C≡N, which consists of a carbon atom triple-bonded to a nitrogen atom. Cyanides most commonly refer to salts of the anion CN−. Most cyanides are highly toxic....

     as a nitrogen
    Nitrogen
    Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...

     source.
  • P. resinovorans
    Pseudomonas resinovorans
    Pseudomonas resinovorans is a Gram-negative, soil bacterium that is commonly found in the lubricating oils of wood mills.It is able to degrade carbazole and as such may be used in bioremediation. Based on 16S rRNA analysis, P. resinovorans has been placed in the P. aeruginosa group....

     can degrade carbazole
    Carbazole
    Carbazole is an aromatic heterocyclic organic compound. It has a tricyclic structure, consisting of two six-membered benzene ring fused on either side of a five-membered nitrogen-containing ring...

    .
  • P. veronii
    Pseudomonas veronii
    Pseudomonas veronii is a Gram-negative, rod-shaped, fluorescent, motile bacterium isolated from natural springs in France. It may be used for bioremediation of contaminated soils, as it has been shown to degrade a variety of simple aromatic organic compounds. Based on 16S rRNA analysis, P. veronii...

     has been shown to degrade a variety of simple aromatic organic compound
    Organic compound
    An organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the...

    s.
  • P. putida
    Pseudomonas putida
    Pseudomonas putida is a gram-negative rod-shaped saprotrophic soil bacterium. Based on 16S rRNA analysis, P. putida has been placed in the P. putida group, to which it lends its name....

     has the ability to degrade organic solvents such as toluene
    Toluene
    Toluene, formerly known as toluol, is a clear, water-insoluble liquid with the typical smell of paint thinners. It is a mono-substituted benzene derivative, i.e., one in which a single hydrogen atom from the benzene molecule has been replaced by a univalent group, in this case CH3.It is an aromatic...

    . At least one strain of this bacterium is able to convert morphine
    Morphine
    Morphine is a potent opiate analgesic medication and is considered to be the prototypical opioid. It was first isolated in 1804 by Friedrich Sertürner, first distributed by same in 1817, and first commercially sold by Merck in 1827, which at the time was a single small chemists' shop. It was more...

     in aqueous solution into the stronger and somewhat expensive to manufacture drug hydromorphone
    Hydromorphone
    Hydromorphone, a more common synonym for dihydromorphinone, commonly a hydrochloride is a very potent centrally-acting analgesic drug of the opioid class. It is a derivative of morphine, to be specific, a hydrogenated ketone thereof and, therefore, a semi-synthetic drug...

     (Dilaudid).
  • Strain KC of P. stutzeri
    Pseudomonas stutzeri
    Pseudomonas stutzeri is a Gram-negative, rod-shaped, motile, single polar-flagellated, soil bacterium first isolated from human spinal fluid.. It is a denitrifying bacterium, and strain KC of P. stutzeri may be used for bioremediation as it is able to degrade carbon tetrachloride. It is also an...

     is able to degrade carbon tetrachloride
    Carbon tetrachloride
    Carbon tetrachloride, also known by many other names is the organic compound with the formula CCl4. It was formerly widely used in fire extinguishers, as a precursor to refrigerants, and as a cleaning agent...

    .

Food spoilage agents

As a result of their metabolic diversity, ability to grow at low temperatures and ubiquitous nature, many Pseudomonas spp. can cause food spoilage. Notable examples include dairy spoilage by P. fragi
Pseudomonas fragi
Pseudomonas fragi is a psychrophilic, Gram-negative bacterium that is responsible for dairy spoilage. Unlike many other members of the Pseudomonas genus, P. fragi does not produce siderophores. Based on 16S rRNA analysis, P. fragi has been placed in the P. chlororaphis group....

, mustiness in eggs caused by P. taetrolens
Pseudomonas taetrolens
Pseudomonas taetrolens is a Gram-negative, non-sporulating, motile, rod bacterium that causes mustiness in eggs. Based on 16S rRNA analysis, P. taetrolens has been placed in the P. chlororaphis group....

 and P. mudicolens
Pseudomonas mucidolens
Pseudomonas mucidolens is a Gram-negative, non-sporulating, motile, rod bacterium that causes mustiness in eggs. Based on 16S rRNA analysis, P. mucidolens has been placed in the P. fluorescens group....

, and P. lundensis
Pseudomonas lundensis
Pseudomonas lundensis is a Gram-negative rod bacterium that often causes spoilage of milk, cheese, meat, and fish. Based on 16S rRNA analysis, P. lundensis has been placed in the P. chlororaphis group....

, which causes spoilage of milk
Milk
Milk is a white liquid produced by the mammary glands of mammals. It is the primary source of nutrition for young mammals before they are able to digest other types of food. Early-lactation milk contains colostrum, which carries the mother's antibodies to the baby and can reduce the risk of many...

, cheese
Cheese
Cheese is a generic term for a diverse group of milk-based food products. Cheese is produced throughout the world in wide-ranging flavors, textures, and forms....

, meat
Meat
Meat is animal flesh that is used as food. Most often, this means the skeletal muscle and associated fat and other tissues, but it may also describe other edible tissues such as organs and offal...

, and fish
Fish (food)
Fish is a food consumed by many species, including humans. The word "fish" refers to both the animal and to the food prepared from it. Fish has been an important source of protein for humans throughout recorded history.-Terminology:...

.

Species previously classified in the genus

Recently, 16S rRNA
16S ribosomal RNA
16S ribosomal RNA is a component of the 30S subunit of prokaryotic ribosomes. It is approximately 1.5kb in length...

 sequence analysis redefined the taxonomy of many bacterial species previously classified as being in the Pseudomonas genus. Species which moved from the Pseudomonas genus are listed below; clicking on a species will show its new classification. Note that the term 'pseudomonad' does not apply strictly to just the Pseudomonas genus, and can be used to also include previous members such as the genera Burkholderia
Burkholderia
Burkholderia is a genus of proteobacteria probably best known for its pathogenic members:Burkholderia mallei, responsible for glanders, a disease that occurs mostly in horses and related animals;...

 and Ralstonia
Ralstonia
Ralstonia is a genus of proteobacteria, previously included in the genus Pseudomonas. It is named after the American bacteriologist E. Ralston.-Genomics:* *...

.

α proteobacteria: P. abikonensis
Sphingomonas abikonensis
Sphingomonas abikonensis is a species of Gram-negative proteobacteria. Following 16S rRNA phylogenetic analysis, it was determined that the organism formerly classified as 'P.' abikonensis belonged in the Sphingomonas rRNA lineage. It is capable of forming freshwater biofilms....

, P. aminovorans
Aminobacter aminovorans
Aminobacter aminovorans is a Gram-negative soil bacteria....

, P. azotocolligans
Sphingomonas trueperi
Sphingomonas trueperi is a Gram-negative soil bacterium....

, P. carboxydohydrogena
Bradyrhizobium
Bradyrhizobium is a genus of Gram-negative soil bacteria, many of which fix nitrogen. Nitrogen fixation is an important part of the nitrogen cycle. Plants cannot use atmospheric nitrogen they must use nitrogen compounds such as nitrates....

, P. carboxidovorans
Oligotropha carboxidovorans
Oligotropha carboxidovorans is a Gram-negative soil bacterium. It is the sole species represented by the genus Oligotropha....

, P. compransoris
Zavarzinia compransoris
Zavarzinia compransoris is a Gram-negative soil bacterium that comprises the only current member of the genus Zavarzinia....

, P. diminuta, P. echinoides
Sphingomonas echinoides
Sphingomonas echinoides is a Gram-negative soil bacterium.http://www.wired.com/wiredscience/2008/05/teen-decomposes/the above is a link to the usage of this bacteria....

, P. extorquens
Methylobacterium extorquens
Methylobacterium extorquens is a Gram-negative bacterium....

, P. lindneri
Zymomonas mobilis
Zymomonas mobilis is a bacterium belonging to the genus Zymomonas. It is notable for its bioethanol-producing capabilities, which surpass yeast in some aspects. It was originally isolated from alcoholic beverages like the African palm wine, the Mexican pulque, and also as a contaminant of cider and...

, P. mesophilica
Methylobacterium mesophilicum
Methylobacterium mesophilicum is a Gram-negative soil bacterium.Methylobacteria are slow-growing, pink-pigmented organisms that have been reported to be opportunistic pathogens in immunocompromised patients. Methylobacterium mesophilicum and Methylobacterium zatmanii have been the two most commonly...

, P. paucimobilis
Sphingomonas paucimobilis
Sphingomonas paucimobilis is an aerobic Gram-negative soil bacillus that has a single polar flagellum with slow motility.S. paucimobilis is able to degrade lignin-related biphenyl chemical compounds....

, P. radiora
Methylobacterium radiotolerans
Methylobacterium radiotolerans is a Gram-negative soil bacterium....

, P. rhodos
Methylobacterium rhodinum
Methylobacterium rhodinum is a Gram-negative soil bacterium....

, P. riboflavina
Devosia riboflavina
Devosia riboflavina is a Gram-negative soil bacteria.someone please put more on this page...

, P. rosea
Methylobacterium extorquens
Methylobacterium extorquens is a Gram-negative bacterium....

, P. vesicularis.

β proteobacteria: P. acidovorans, P. alliicola
Burkholderia gladioli
Burkholderia gladioli is a species of aerobic gram-negative rod-shaped bacteria that causes disease in both humans and plants. It can also live in symbiosis with plants and fungi and is found in soil, water, the rhizosphere, and in many animals...

, P. antimicrobica
Burkholderia gladioli
Burkholderia gladioli is a species of aerobic gram-negative rod-shaped bacteria that causes disease in both humans and plants. It can also live in symbiosis with plants and fungi and is found in soil, water, the rhizosphere, and in many animals...

, P. avenae
Acidovorax avenae
Acidovorax avenae is a Gram-negative soil bacterium. A. avenae subsp. citrulli is the causal agent of bacterial fruit blotch....

, P. butanovorae
Thauera
Thauera is a genus of Gram-negative bacteria named after the German Microbiologist Rudolf Thauer. Most species of this genus are motile by flagellas and are mostly rod-shaped. The species occur in wet soil and polluted freshwater....

, P. caryophylli
Burkholderia caryophylli
Burkholderia caryophylli is a plant pathogenic bacterium, which can cause wilt, foot and root rot on carnation....

, P. cattleyae
Acidovorax avenae
Acidovorax avenae is a Gram-negative soil bacterium. A. avenae subsp. citrulli is the causal agent of bacterial fruit blotch....

, P. cepacia, P. cocovenenans, P. delafieldii
Acidovorax delafieldii
Acidovorax delafieldii is a Gram-negative soil bacterium....

, P. facilis
Acidovorax facilis
Acidovorax facilis is an aerobic, chemoorganotrophic bacterium used as a soil inoculant in agriculture and horticulture.-Morphological and biochemical attributes:...

, P. flava
Hydrogenophaga flava
Hydrogenophaga flava is a species of Comamonad bacteria....

, P. gladioli
Burkholderia gladioli
Burkholderia gladioli is a species of aerobic gram-negative rod-shaped bacteria that causes disease in both humans and plants. It can also live in symbiosis with plants and fungi and is found in soil, water, the rhizosphere, and in many animals...

, P. glathei
Burkholderia glathei
Burkholderia glathei is a Gram-negative soil bacterium. It is motile by using one polar flagellum. The bacterium is pathogen for Asian Rice ....

, P. glumae
Burkholderia glumae
Burkholderia glumae is a Gram-negative soil bacterium....

, P. graminis
Burkholderia graminis
Burkholderia graminis is a species of proteobacteria....

, P. huttiensis
Herbaspirillum huttiense
Herbaspirillum huttiense is a species of Gram-negative bacteria....

, P. indigofera
Vogesella indigofera
Vogesella indigofera is a strictly aerobic, Gram-negative bacterium. It is the sole species of the genus Vogesella. V. indigofera produces a blue pigment and the colonies develop a metallic copper sheen upon extended incubation . This organism is not known to be pathogenic and is commonly found in...

, P. lanceolata
Comamonadaceae
The Comamonadaceae are a family of the Beta Proteobacteria. Like all Proteobacteria, they are Gram-negative. They are aerobic and most of the species are motile via flagella and curved rod-shaped.-References:...

, P. lemoignei
Paucimonas lemoignei
Paucimonas lemoignei is a Gram-negative soil bacterium. It is aerobe, motile and rod-shaped. Paucimonas lemoignei is named after the French microbiologist Maurice Lemoigne.-External links:...

, P. mallei
Burkholderia mallei
Burkholderia mallei is a gram-negative bipolar aerobic bacterium, a Burkholderia-genus human and animal pathogen causing Glanders; the Latin name of this disease gave name to the causative agent species...

, P. mephitica, P. mixta
Telluria mixta
The Telluria are a genus of Gram-negative soil bacteria....

, P. palleronii, P. phenazinium
Burkholderia phenazinium
Burkholderia phenazinium is a Gram-negative soil bacterium....

, P. pickettii
Ralstonia pickettii
Ralstonia pickettii is a Gram-negative soil bacterium....

, P. plantarii
Burkholderia plantarii
Burkholderia plantarii is a Gram-negative soil bacterium....

, P. pseudoflava, P. pseudomallei
Burkholderia pseudomallei
Burkholderia pseudomallei is a Gram-negative, bipolar, aerobic, motile rod-shaped bacterium. It infects humans and animals and causes the disease melioidosis. It is also capable of infecting plants....

, P. pyrrocinia
Burkholderia pyrrocinia
Burkholderia pyrrocinia is a Gram-negative soil bacterium....

, P. rubrilineans
Acidovorax avenae
Acidovorax avenae is a Gram-negative soil bacterium. A. avenae subsp. citrulli is the causal agent of bacterial fruit blotch....

, P. rubrisubalbicans, P. saccharophila, P. solanacearum
Ralstonia solanacearum
Ralstonia solanacearum is an aerobic non-sporing, Gram-negative plant pathogenic bacterium. R. solanacearum is soil-borne and motile with a polar flagellar tuft. It colonises the xylem, causing bacterial wilt in a very wide range of potential host plants...

, P. spinosa
Hydrogenophaga
Hydrogenophaga is a genus of Comamonad bacteria, several of which were formerly classified in the genus Pseudomonas....

, P. syzygii
Ralstonia syzygii
Ralstonia syzigii is a Gram-negative soil bacterium....

, P. taeniospiralis, P. terrigena, P. testosteroni
Comamonas testosteroni
Comamonas testosteroni is a Gram-negative soil bacterium. Strain I2gfp has been used in bioaugmentation trials, in attempts to treat the industrial by-product 3-chloroaniline....

.

γ-β proteobacteria: P. beteli
Stenotrophomonas
Stenotrophomonas is a genus of Gram-negative bacteria. With species ranging from common soil organisms to opportunistic human pathogens , the molecular taxonomy of the genus is still somewhat unclear....

, P. boreopolis
Xanthomonas
Xanthomonas is a genus of Proteobacteria, many of which cause plant diseases. Most varieties of Xanthomonas are available from the National Collection of Plant Pathogenic Bacteria in the United Kingdom and other international culture collections such as ICMP in New Zealand, CFBP in France, and...

, P. cissicola
Xanthomonas
Xanthomonas is a genus of Proteobacteria, many of which cause plant diseases. Most varieties of Xanthomonas are available from the National Collection of Plant Pathogenic Bacteria in the United Kingdom and other international culture collections such as ICMP in New Zealand, CFBP in France, and...

, P. geniculata
Stenotrophomonas
Stenotrophomonas is a genus of Gram-negative bacteria. With species ranging from common soil organisms to opportunistic human pathogens , the molecular taxonomy of the genus is still somewhat unclear....

, P. hibiscicola
Stenotrophomonas
Stenotrophomonas is a genus of Gram-negative bacteria. With species ranging from common soil organisms to opportunistic human pathogens , the molecular taxonomy of the genus is still somewhat unclear....

, P. maltophilia
Stenotrophomonas maltophilia
Stenotrophomonas maltophilia is an aerobic, nonfermentative, Gram-negative bacterium. It is an uncommon bacterium and human infection is difficult to treat. Initially classified as Pseudomonas maltophilia, S. maltophilia was also grouped in the genus Xanthomonas before eventually becoming the type...

, P. pictorum
Stenotrophomonas
Stenotrophomonas is a genus of Gram-negative bacteria. With species ranging from common soil organisms to opportunistic human pathogens , the molecular taxonomy of the genus is still somewhat unclear....

.

γ proteobacteria: P. beijerinckii
Chromohalobacter
Chromohalobacter is a genus of Proteobacteria. It was established by Ventosa and others in 1989, with the reclassification of Chromobacterium marismortui as Chromohalobacter marismortui. As of 2007, it comprised the following species:...

, P. diminuta, P. doudoroffii
Aeromonas
Aeromonas is a gram-negative, facultative anaerobic rod that morphologically resembles members of the family Enterobacteriaceae. Fourteen species of Aeromonas have been described, most of which have been associated with human diseases. The most important pathogens are A. hydrophila, A. caviae, and...

, P. elongata
Microbulbifer elongatus
Microbulbifer elongatus is a Gram-negative marine bacterium....

, P. flectens
Enterobacteriaceae
The Enterobacteriaceae is a large family of bacteria that includes many of the more familiar pathogens, such as Salmonella, Escherichia coli, Yersinia pestis, Klebsiella and Shigella. This family is the only representative in the order Enterobacteriales of the class Gammaproteobacteria in the...

, P. halodurans
Halomonas halodurans
Halomonas halodurans is a Gram-negative halophilic Proteobacteria....

, P. halophila
Marinobacter
Marinobacter is a genus of Proteobacteria found in sea water. A number of strains and species can degrade hydrocarbons; M. alkaliphilus, M. aquaeolei, M. arcticus, M. hydrocarbonoclasticus, M. maritimus & M. squalenivorans....

, P. iners
Marinobacterium georgiense
Marinobacterium georgiense is a Gram-negative bacterium....

, P. marina
Halomonadaceae
The Halomonadaceae are a family of halophilic Proteobacteria.-History:The family was originally created in 1988 to contain the genera Halomonas and Deleya....

, P. nautica
Marinobacter hydrocarbonoclasticus
Marinobacter hydrocarbonoclasticus is a species of Proteobacteria found in sea water which are able to degrade hydrocarbons. The cells are rod-shaped and motile by means of a single polar flagellum....

, P. nigrifaciens
Pseudoalteromonas nigrifaciens
Pseudoalteromonas nigrifaciens is a marine bacterium. It has been observed to cause skin ulcer syndrome in juvenile cultivated sea cucumbers....

, P. pavonacea
Acinetobacter
Acinetobacter [asz−in−ée−toe–back−ter] is a genus of Gram-negative bacteria belonging to the Gammaproteobacteria. Acinetobacter species are non-motile and oxidase-negative, and occur in pairs under magnification....

, P. piscicida
Pseudoalteromonas piscicida
Pseudoalteromonas piscicida is a marine bacterium....

, P. stanieri
Marinobacterium stanieri
Marinobacterium stanieri is a Gram-negative bacterium found in sea water....

.

δ proteobacteria: P. formicans...

Footnotes

General

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