Bacteroidetes
Encyclopedia
The phylum Bacteroidetes is composed of three large classes of bacteria
that are widely distributed in the environment, including in soil, in sediments, sea water and in the guts and on the skin of animals.
By far, the ones in the Bacteroidia
class
are the most well-studied, including the genus Bacteroides
(an abundant organism in the feces
of warm-blooded animals including humans), and Porphyromonas, a group of organisms inhabiting the human oral cavity. The class Bacteroidia was formally called Bacteroidetes as it was until recently the only class in the phylum, the name was changed in the fourth volume of Bergey's Manual of Systematic Bacteriology.
Members of the genus Bacteroides are opportunistic
pathogen
s. Rarely are members of the other two classes pathogenic to humans.
Researcher Jeffrey Gordon
and his colleagues found that obese humans and mice had intestinal flora (gut flora
) with a lower percentage of Bacteroidetes and relatively more bacteria from the Firmicutes
family. However, they are unsure if Bacteroidetes prevent obesity
or if these intestinal flora are merely preferentially selected by intestinal conditions in those who are not obese.
This phylum is sometimes grouped with Chlorobi, Fibrobacteres, Gemmatimonadates, Caldithrix and Marine group A to form the FCB group or superphylum. In the alternative classification system proposed by Cavalier-Smith, this taxa is instead a class in the Sphingobacteria
phylum.
and the phylogeny is based on 16S rRNA-based LTP release 106 by The All-Species Living Tree Project
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...
that are widely distributed in the environment, including in soil, in sediments, sea water and in the guts and on the skin of animals.
By far, the ones in the Bacteroidia
Bacteroidetes (class)
The class Bacteroidia is composed of a single order of environmental bacteria. By far, the Bacteroidales class are the most well-studied of the Bacteroidetes. Some members of the genus Bacteroides are opportunistic pathogens. Before the fourth volume of Bergey's Manual of Systematic Bacteriology...
class
Class (biology)
In biological classification, class is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, order, family, genus, and species, with class fitting between phylum and order...
are the most well-studied, including the genus Bacteroides
Bacteroides
Bacteroides is a genus of Gram-negative, bacillus bacteria. Bacteroides species are non-endospore-forming, anaerobes, and may be either motile or non-motile, depending on the species. The DNA base composition is 40-48% GC. Unusual in bacterial organisms, Bacteroides membranes contain sphingolipids...
(an abundant organism in the feces
Feces
Feces, faeces, or fæces is a waste product from an animal's digestive tract expelled through the anus or cloaca during defecation.-Etymology:...
of warm-blooded animals including humans), and Porphyromonas, a group of organisms inhabiting the human oral cavity. The class Bacteroidia was formally called Bacteroidetes as it was until recently the only class in the phylum, the name was changed in the fourth volume of Bergey's Manual of Systematic Bacteriology.
Members of the genus Bacteroides are opportunistic
Opportunistic infection
An opportunistic infection is an infection caused by pathogens, particularly opportunistic pathogens—those that take advantage of certain situations—such as bacterial, viral, fungal or protozoan infections that usually do not cause disease in a healthy host, one with a healthy immune system...
pathogen
Pathogen
A pathogen gignomai "I give birth to") or infectious agent — colloquially, a germ — is a microbe or microorganism such as a virus, bacterium, prion, or fungus that causes disease in its animal or plant host...
s. Rarely are members of the other two classes pathogenic to humans.
Researcher Jeffrey Gordon
Jeffrey I. Gordon
Jeffrey I. Gordon, M.D., is a biologist and the Dr. Robert J. Glaser Distinguished University Professor and Director of the Center for Genome Sciences at Washington University, St. Louis...
and his colleagues found that obese humans and mice had intestinal flora (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....
) with a lower percentage of Bacteroidetes and relatively more bacteria from the 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...
family. However, they are unsure if Bacteroidetes prevent obesity
Obesity
Obesity is a medical condition in which excess body fat has accumulated to the extent that it may have an adverse effect on health, leading to reduced life expectancy and/or increased health problems...
or if these intestinal flora are merely preferentially selected by intestinal conditions in those who are not obese.
This phylum is sometimes grouped with Chlorobi, Fibrobacteres, Gemmatimonadates, Caldithrix and Marine group A to form the FCB group or superphylum. In the alternative classification system proposed by Cavalier-Smith, this taxa is instead a class in the Sphingobacteria
Sphingobacteria (phylum)
Sphingobacteria is a division , created by Cavalier-Smith, which contains the classes Chlorobea, Fibrobacteres, Bacteroidetes and Flavobacteria....
phylum.
Phylogeny
The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LSPN)and the phylogeny is based on 16S rRNA-based LTP release 106 by The All-Species Living Tree Project
External links
- Phylogenomics and Evolutionary Studies on Bacteriodetes, Chlorobi and Fibrobacteres Species Bacterial (Prokaryotic) Phylogeny Webpage