Lactobacillus
Overview

Lactobacillus 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 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...

 facultative anaerobic or microaerophilic rod-shaped bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

. They are a major part of the lactic acid bacteria
Lactic acid bacteria
The lactic acid bacteria comprise a clade of Gram-positive, low-GC, acid-tolerant, generally non-sporulating, non-respiring rod or cocci that are associated by their common metabolic and physiological characteristics. These bacteria, usually found in decomposing plants and lactic products, produce...

 group, named as such because most of its members convert lactose
Lactose
Lactose is a disaccharide sugar that is found most notably in milk and is formed from galactose and glucose. Lactose makes up around 2~8% of milk , although the amount varies among species and individuals. It is extracted from sweet or sour whey. The name comes from or , the Latin word for milk,...

 and other sugars to lactic acid
Lactic acid
Lactic acid, also known as milk acid, is a chemical compound that plays a role in various biochemical processes and was first isolated in 1780 by the Swedish chemist Carl Wilhelm Scheele. Lactic acid is a carboxylic acid with the chemical formula C3H6O3...

. They are common and usually benign. In humans they are present in the vagina
Vagina
The vagina is a fibromuscular tubular tract leading from the uterus to the exterior of the body in female placental mammals and marsupials, or to the cloaca in female birds, monotremes, and some reptiles. Female insects and other invertebrates also have a vagina, which is the terminal part of the...

 and the gastrointestinal tract
Gastrointestinal tract
The human gastrointestinal tract refers to the stomach and intestine, and sometimes to all the structures from the mouth to the anus. ....

, where they are symbiotic and make up a small portion of the gut flora
Gut flora
Gut flora consists of microorganisms that live in the digestive tracts of animals and is the largest reservoir of human flora. In this context, gut is synonymous with intestinal, and flora with microbiota and microflora....

.
Encyclopedia

Lactobacillus 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 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...

 facultative anaerobic or microaerophilic rod-shaped bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

. They are a major part of the lactic acid bacteria
Lactic acid bacteria
The lactic acid bacteria comprise a clade of Gram-positive, low-GC, acid-tolerant, generally non-sporulating, non-respiring rod or cocci that are associated by their common metabolic and physiological characteristics. These bacteria, usually found in decomposing plants and lactic products, produce...

 group, named as such because most of its members convert lactose
Lactose
Lactose is a disaccharide sugar that is found most notably in milk and is formed from galactose and glucose. Lactose makes up around 2~8% of milk , although the amount varies among species and individuals. It is extracted from sweet or sour whey. The name comes from or , the Latin word for milk,...

 and other sugars to lactic acid
Lactic acid
Lactic acid, also known as milk acid, is a chemical compound that plays a role in various biochemical processes and was first isolated in 1780 by the Swedish chemist Carl Wilhelm Scheele. Lactic acid is a carboxylic acid with the chemical formula C3H6O3...

. They are common and usually benign. In humans they are present in the vagina
Vagina
The vagina is a fibromuscular tubular tract leading from the uterus to the exterior of the body in female placental mammals and marsupials, or to the cloaca in female birds, monotremes, and some reptiles. Female insects and other invertebrates also have a vagina, which is the terminal part of the...

 and the gastrointestinal tract
Gastrointestinal tract
The human gastrointestinal tract refers to the stomach and intestine, and sometimes to all the structures from the mouth to the anus. ....

, where they are symbiotic and make up a small portion of the gut flora
Gut flora
Gut flora consists of microorganisms that live in the digestive tracts of animals and is the largest reservoir of human flora. In this context, gut is synonymous with intestinal, and flora with microbiota and microflora....

. Many species are prominent in decaying plant material. The production of lactic acid makes its environment acidic, which inhibits the growth of some harmful bacteria. Several members of the genus have had their 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....

 sequenced.

Food production

Some Lactobacillus species are used for the production of yogurt
Yoghurt
Yoghurt, yogurt or yogourt is a dairy product produced by bacterial fermentation of milk. The bacteria used to make yoghurt are known as "yoghurt cultures"...

, 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....

, sauerkraut
Sauerkraut
Sauerkraut , directly translated from German: "sour cabbage", is finely shredded cabbage that has been fermented by various lactic acid bacteria, including Leuconostoc, Lactobacillus, and Pediococcus. It has a long shelf-life and a distinctive sour flavor, both of which result from the lactic acid...

, pickle
Pickling
Pickling, also known as brining or corning is the process of preserving food by anaerobic fermentation in brine to produce lactic acid, or marinating and storing it in an acid solution, usually vinegar . The resulting food is called a pickle. This procedure gives the food a salty or sour taste...

s, beer
Beer
Beer is the world's most widely consumed andprobably oldest alcoholic beverage; it is the third most popular drink overall, after water and tea. It is produced by the brewing and fermentation of sugars, mainly derived from malted cereal grains, most commonly malted barley and malted wheat...

, wine
Wine
Wine is an alcoholic beverage, made of fermented fruit juice, usually from grapes. The natural chemical balance of grapes lets them ferment without the addition of sugars, acids, enzymes, or other nutrients. Grape wine is produced by fermenting crushed grapes using various types of yeast. Yeast...

, cider
Cider
Cider or cyder is a fermented alcoholic beverage made from apple juice. Cider varies in alcohol content from 2% abv to 8.5% abv or more in traditional English ciders. In some regions, such as Germany and America, cider may be termed "apple wine"...

, kimchi
Kimchi
Kimchi , also spelled gimchi, kimchee, or kim chee, is a traditional fermented Korean dish made of vegetables with varied seasonings. There are hundreds of varieties of kimchi made with a main vegetable ingredient such as napa cabbage, radish, green onions or cucumber. It is the most common...

, chocolate
Chocolate
Chocolate is a raw or processed food produced from the seed of the tropical Theobroma cacao tree. Cacao has been cultivated for at least three millennia in Mexico, Central and South America. Its earliest documented use is around 1100 BC...

, and other fermented
Fermentation (food)
Fermentation in food processing typically is the conversion of carbohydrates to alcohols and carbon dioxide or organic acids using yeasts, bacteria, or a combination thereof, under anaerobic conditions. Fermentation in simple terms is the chemical conversion of sugars into ethanol...

 foods, as well as animal feeds, such as silage
Silage
Silage is fermented, high-moisture fodder that can be fed to ruminants or used as a biofuel feedstock for anaerobic digesters. It is fermented and stored in a process called ensiling or silaging, and is usually made from grass crops, including corn , sorghum or other cereals, using the entire...

. Sourdough
Sourdough
Sourdough is a dough containing a Lactobacillus culture, usually in symbiotic combination with yeasts. It is one of two principal means of biological leavening in bread baking, along with the use of cultivated forms of yeast . It is of particular importance in baking rye-based breads, where yeast...

 bread is made using a "starter culture," which is a symbiotic culture of yeast
Yeast
Yeasts are eukaryotic micro-organisms classified in the kingdom Fungi, with 1,500 species currently described estimated to be only 1% of all fungal species. Most reproduce asexually by mitosis, and many do so by an asymmetric division process called budding...

 and lactic acid bacteria
Lactic acid bacteria
The lactic acid bacteria comprise a clade of Gram-positive, low-GC, acid-tolerant, generally non-sporulating, non-respiring rod or cocci that are associated by their common metabolic and physiological characteristics. These bacteria, usually found in decomposing plants and lactic products, produce...

 growing in a water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...

 and flour
Flour
Flour is a powder which is made by grinding cereal grains, other seeds or roots . It is the main ingredient of bread, which is a staple food for many cultures, making the availability of adequate supplies of flour a major economic and political issue at various times throughout history...

 medium
Growth medium
A growth medium or culture medium is a liquid or gel designed to support the growth of microorganisms or cells, or small plants like the moss Physcomitrella patens.There are different types of media for growing different types of cells....

. Lactobacilli, especially L. casei
Lactobacillus casei
Lactobacillus casei is a species of genus Lactobacillus found in the human intestine and mouth. As a lactic acid producer, it has been found to assist in the propagation of desirable bacteria. This particular species of Lactobacillus is documented to have a wide pH and temperature range, and...

and L. brevis
Lactobacillus brevis
Lactobacillus brevis is a species of lactic acid bacteria. It can be found in many different environments and in fermented foods such as sauerkraut and pickles. It is also one of the most common causes of beer spoilage. Ingestion has been shown to improve human immune function, and it has been...

, are some of the most common beer spoilage organisms.
The species operate by lowering the pH of the fermenting substance by creating the lactic acid, neutralising it to the desired extent.

Probiotics and biotherapeutics

Some Lactobacillus spp. and other lactic acid bacteria may possess potential therapeutic properties including anti-inflammatory and anti-cancer
Cancer
Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...

 activities, as well as other features of interest. A study by researchers from the Beth Israel Deaconess Medical Center and UCLA in 2009 demonstrated the protective effects of some strains of these bacteria for anti-tumor and anti-cancer effects. Dietary administration alleviated the risks of certain types of cancers and suppressed colonic tumor incidence, volume and multiplicity induced by various carcinogen
Carcinogen
A carcinogen is any substance, radionuclide, or radiation that is an agent directly involved in causing cancer. This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes...

s in mice. For a few strains oral administration effectively reduced DNA
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...

 adduct
Adduct
An adduct is a product of a direct addition of two or more distinct molecules, resulting in a single reaction product containing all atoms of all components. The resultant is considered a distinct molecular species...

 formation, ameliorated DNA damage and prevented putative preneoplastic lesions such as aberrant crypt foci
Aberrant crypt foci
Aberrant crypt foci are clusters of abnormal tube-like glands in the lining of the colon and rectum. Aberrant crypt foci form before colorectal polyps and are one of the earliest changes seen in the colon that may lead to cancer. ACF are, as opposed to normal epithelial cells, apoptosis resistant...

 induced by chemical carcinogens in the gastrointestinal tract
Gastrointestinal tract
The human gastrointestinal tract refers to the stomach and intestine, and sometimes to all the structures from the mouth to the anus. ....

. Reports also indicated that some cultures administered to animals inhibited liver, colon, bladder, and mammary tumors, highlighting potential systemic effects of probiotic
Probiotic
Probiotics are live microorganisms thought to be beneficial to the host organism. According to the currently adopted definition by FAO/WHO, probiotics are: "Live microorganisms which when administered in adequate amounts confer a health benefit on the host"...

s with anti-neoplastic activities.

Lactobacilli are also used to restore particular physiological balance such as in the vaginal eco-system. Their role is (1) to physically protect the vaginal epithelium by building a thick layer separating the epithelium from pathogens, (2) to physiologically keep the balance of the vaginal ecosystem in maintaining the pH at ~4.5 and (3) generating hydrogen peroxide
Hydrogen peroxide
Hydrogen peroxide is the simplest peroxide and an oxidizer. Hydrogen peroxide is a clear liquid, slightly more viscous than water. In dilute solution, it appears colorless. With its oxidizing properties, hydrogen peroxide is often used as a bleach or cleaning agent...

 against pathogens.Lactobacillus is highly tolerant to low pH and can easily maintain low pH and protect the vaginal eco-system from gram negative and gram positive bacteria

At least one Lactobacillus species in the colon may play a role in defense against flu viruses. Antibiotics that kill Lactobacillus seem to impair production of interleukin-1 beta (IL-1 beta), which is necessary to combat influenza and some other viruses.

Taxonomy

The genus Lactobacillus currently consists of over 125 species and encompasses a wide variety of organisms. The genus is polyphyletic, with the genus Pediococcus
Pediococcus
Pediococcus is a genus of Gram-positive lactic acid bacteria, placed within the family of Lactobacillaceae. They usually occur in pairs or tetrads, and divide along two planes of symmetry, as do the other lactic acid cocci genera Aerococcus and Tetragenococcus. They are purely homofermentative...

dividing the L. casei group, and the species L. acidophilus, L. salivarius, and L. reuteri being representatives of three distinct subclades. The genus Paralactobacillus falls within the L. salivarius group. In recent years, other members of the genus Lactobacillus (formerly known as the Leuconostoc branch of Lactobacillus) have been reclassified into the genera Atopobium
Atopobium
Atopobium is a genus of Actinobacteria, in the family Coriobacteriaceae.Atopobium species are anaerobic bacteria, Gram-positive rod-shaped or elliptical found as single elements or in pairs or short chains....

, Carnobacterium
Carnobacterium
Carnobacterium is a genus of Gram-positive bacteria within the family Leuconostocaceae. C. divergens and C. maltaromaticum are found in the wild and in food products and can grow anaerobically. These species are not known to be pathogenic in humans but may cause disease in fish....

, Weissella
Weissella
Weissella is a genus of Gram-positive bacteria, placed within the family of Leuconostocaceae. The morphology of weissellas varies from spherical or lenticular cells to irregular rods.-External links:**...

, Oenococcus
Oenococcus
Oenococcus is a genus of Gram-positive bacteria, placed within the family of Leuconostocaceae. The only species in the genus used to be Oenococcus oeni . In 2006, the species Oenococcus kitaharae was identified...

, and Leuconostoc
Leuconostoc
Leuconostoc is a genus of Gram-positive bacteria, placed within the family of Leuconostocaceae. They are generally ovoid cocci often forming chains. Leuconostoc spp. are intrinsically resistant to vancomycin and are catalase-negative . All species within this genus are heterofermentative and are...

. More recently, the Pediococcus
Pediococcus
Pediococcus is a genus of Gram-positive lactic acid bacteria, placed within the family of Lactobacillaceae. They usually occur in pairs or tetrads, and divide along two planes of symmetry, as do the other lactic acid cocci genera Aerococcus and Tetragenococcus. They are purely homofermentative...

species P. dextrinicus has been reclassified as a Lactobacillus species (IJSEM, Paper in Press).

Dental caries

Although considered beneficial, some Lactobacillus species have been associated with dental caries
Dental caries
Dental caries, also known as tooth decay or a cavity, is an irreversible infection usually bacterial in origin that causes demineralization of the hard tissues and destruction of the organic matter of the tooth, usually by production of acid by hydrolysis of the food debris accumulated on the...

. The Lactobacillus count in saliva has been used as a "caries test" for many years. This is one of the arguments used in support of the use of fluoride
Fluoride
Fluoride is the anion F−, the reduced form of fluorine when as an ion and when bonded to another element. Both organofluorine compounds and inorganic fluorine containing compounds are called fluorides. Fluoride, like other halides, is a monovalent ion . Its compounds often have properties that are...

 in toothpaste
Toothpaste
Toothpaste is a paste or gel dentifrice used with a toothbrush as an accessory to clean and maintain the aesthetics and health of teeth. Toothpaste is used to promote oral hygiene: it serves as an abrasive that aids in removing the dental plaque and food from the teeth, assists in suppressing...

 and lozenges
Throat lozenge
A throat lozenge, cough drop, troche, or cough sweet is a small, medicated tablet intended to be dissolved slowly in the mouth to temporarily stop coughs and lubricate and soothe irritated tissues of the throat , possibly from the common cold or influenza...

. Lactobacillus characteristically causes existing carious lesions to progress, especially those in coronal caries.

Metabolism

Many lactobacilli are unusual in that they operate using homofermentative metabolism (that is, they produce only lactic acid from sugars in contrast to heterofermentative lactobacilli which can produce either alcohol or lactic acid from sugars) and are aerotolerant despite the complete absence of a respiratory chain. This aerotolerance is manganese
Manganese
Manganese is a chemical element, designated by the symbol Mn. It has the atomic number 25. It is found as a free element in nature , and in many minerals...

-dependent and has been explored (and explained) in Lactobacillus plantarum
Lactobacillus plantarum
Lactobacillus plantarum is a widespread member of the genus Lactobacillus, commonly found in many fermented food products as well as anaerobic plant matter. It is also present in saliva . It has the ability to liquefy gelatin. L...

. Many lactobacilli do not require iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...

 for growth and have an extremely high hydrogen peroxide
Hydrogen peroxide
Hydrogen peroxide is the simplest peroxide and an oxidizer. Hydrogen peroxide is a clear liquid, slightly more viscous than water. In dilute solution, it appears colorless. With its oxidizing properties, hydrogen peroxide is often used as a bleach or cleaning agent...

 tolerance.

According to metabolism, Lactobacillus species can be divided into three groups:
  • Obligately homofermentative (Group I)
    • L. acidophilus
      Lactobacillus acidophilus
      Lactobacillus acidophilus is a species in the genus Lactobacillus. L. acidophilus is a homofermentative species, fermenting sugars into lactic acid, which grows readily at rather low pH values and has an optimum growth temperature of 37 °C . L...

      , L. delbrueckii, L. helveticus
      Lactobacillus helveticus
      Lactobacillus helveticus is a lactic-acid producing rod shaped bacterium of the genus Lactobacillus. It is most commonly used in the production of American Swiss cheese and Emmental cheese but is also sometimes used in making other styles of cheese, such as Cheddar, Parmesan, romano, provolone,...

      , L. salivarius
  • Facultatively heterofermentative (Group II)
    • L. casei
      Lactobacillus casei
      Lactobacillus casei is a species of genus Lactobacillus found in the human intestine and mouth. As a lactic acid producer, it has been found to assist in the propagation of desirable bacteria. This particular species of Lactobacillus is documented to have a wide pH and temperature range, and...

      , L. curvatus, L. plantarum
      Lactobacillus plantarum
      Lactobacillus plantarum is a widespread member of the genus Lactobacillus, commonly found in many fermented food products as well as anaerobic plant matter. It is also present in saliva . It has the ability to liquefy gelatin. L...

      , L. sakei
  • Obligately heterofermentative (Group III)
    • L. brevis
      Lactobacillus brevis
      Lactobacillus brevis is a species of lactic acid bacteria. It can be found in many different environments and in fermented foods such as sauerkraut and pickles. It is also one of the most common causes of beer spoilage. Ingestion has been shown to improve human immune function, and it has been...

      , L. buchneri
      Lactobacillus buchneri
      Lactobacillus buchneri is a heterofermentative bacteria that produces lactic acid and acetic acid during Fermentation . It is used as a bacterial inoculant to improve the aerobic stability of silage.-References:...

      , L. fermentum
      Lactobacillus fermentum
      Lactobacillus fermentum is a Gram-positive species of bacterium in the genus Lactobacillus. It is associated with active dental caries lesions. It is also commonly found in fermenting animal and plant material. It has been found in sourdough...

      , L. reuteri
      Lactobacillus reuteri
      Lactobacillus reuteri is a Gram-positive bacterium that naturally inhabits the gut of mammals and birds. First described in the early 1980s, some strains of L. reuteri are used as probiotics. BioGaia AB in Sweden owns several commercially important strains and a large number of different patents...


See also

  • Firmicutes
    Firmicutes
    The Firmicutes are a phylum of bacteria, most of which have Gram-positive cell wall structure. A few, however, such as Megasphaera, Pectinatus, Selenomonas and Zymophilus, have a porous pseudo-outer-membrane that causes them to stain Gram-negative...

  • Lactic acid bacteria
    Lactic acid bacteria
    The lactic acid bacteria comprise a clade of Gram-positive, low-GC, acid-tolerant, generally non-sporulating, non-respiring rod or cocci that are associated by their common metabolic and physiological characteristics. These bacteria, usually found in decomposing plants and lactic products, produce...

  • Lactic acid fermentation
    Lactic acid fermentation
    Lactic acid fermentation is a biological process by which sugars such as glucose, fructose, and sucrose, are converted into cellular energy and the metabolic byproduct lactate. It is an anaerobic fermentation reaction that occurs in some bacteria and animal cells, such as muscle cells, in the...

  • Paralactobacillus
  • Pediococcus
    Pediococcus
    Pediococcus is a genus of Gram-positive lactic acid bacteria, placed within the family of Lactobacillaceae. They usually occur in pairs or tetrads, and divide along two planes of symmetry, as do the other lactic acid cocci genera Aerococcus and Tetragenococcus. They are purely homofermentative...

  • Probiotics

External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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