''Parabacteroides'' is a

Gram-negative Gram-negative bacteria are bacteria that do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. They are characterized by their cell envelopes, which are composed of a thin peptidoglycan cell wall ...

anaerobic Anaerobic means "living, active, occurring, or existing in the absence of free oxygen", as opposed to aerobic which means "living, active, or occurring only in the presence of oxygen." Anaerobic may also refer to: * Anaerobic adhesive, a bonding a ...

, non-

spore In biology, a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plants, algae, f ...

-forming genus from the family ''

Tannerellaceae "''Tannerellaceae''" is a family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family ...

''. First isolated from fecal specimen in 1933, type strain ''

Parabacteroides distasonis ''Parabacteroides distasonis'' is a Gram-negative, non-sporeforming, obligately anaerobic, rod-shaped, and non-motile bacterium from the genus of Parabacteroides ''Parabacteroides'' is a Gram-negative, anaerobic, non-spore-forming genus from ...

'' was originally classified under the name ''Bacteroides distasonis.'' The strain was re-classified to form the new genus ''Parabacteroides'' in 2006. ''Parabacteroides'' currently comprise 21 phylogenetically, ecologically, and metabolically diverse species, 11 of which are validly published in the taxonomic database

List of Prokaryotic names with Standing in Nomenclature List of Prokaryotic names with Standing in Nomenclature (LPSN) is an online database that maintains information on the naming and taxonomy of prokaryotes, following the taxonomy requirements and rulings of the International Code of Nomenclature ...

(LPSN). Within the ''Parabacteroides'' genus, species '' P. distasonis and P. goldsteinii'' have been associated with beneficial effects in human health, relating to their integral role in

gut microbiota Gut microbiota, gut microbiome, or gut flora, are the microorganisms, including bacteria, archaea, fungi, and viruses that live in the digestive tracts of animals. The gastrointestinal metagenome is the aggregate of all the genomes of the gut m ...

along the digestive tract.

Taxonomy

The

taxon In biology, a taxon (back-formation from ''taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular nam ...

ID number used for prokaryotic genus ''Parabacteroides'' is 516255. Parent taxon comes from bacterial family ''

,'' identified by number 29533 in the online

LPSN List of Prokaryotic names with Standing in Nomenclature (LPSN) is an online database that maintains information on the naming and taxonomy of prokaryotes, following the taxonomy requirements and rulings of the International Code of Nomenclature ...

database.

Genomics

The genomes of ''Parabacteroides'' are highly variable, both across species and within a single strain. For example, genomes isolated from type strain '' P. distasonis'' range in size from approximately 4.5 to 5.2 Mb (

megabases A base pair (bp) is a fundamental unit of double-stranded nucleic acids consisting of two nucleobases bound to each other by hydrogen bonds. They form the building blocks of the DNA double helix and contribute to the folded structure of both DN ...

) and encode over 2,000 functional

proteins Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...

, signifying substantial variation within the species.

Species

The genus ''Parabacteroides'' comprises the following species, 11 of which are validly published by the

(LPSN):

Role in the human gut microenvironment

Part of the bacterial order ''

Bacteroidales Bacteroidales is an order of bacteria. Notably it includes the genera ''Prevotella'' and ''Bacteroides'' , which are commonly found in the human gut microbiota. Phylogeny The currently accepted taxonomy is based on the List of Prokaryotic name ...

'' present in the human gut, ''Parabacteroides'' are commonly found within the gut microenvironment. ''Parabacteroides'' species constitute a significant component of

microbiota Microbiota are the range of microorganisms that may be commensal, symbiotic, or pathogenic found in and on all multicellular organisms, including plants. Microbiota include bacteria, archaea, protists, fungi, and viruses, and have been found t ...

along the

digestive tract The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the digestive system that leads from the mouth to the anus. The GI tract contains all the major organs of the digestive system, in humans a ...

, benefitting from a

commensal relationship Commensalism is a long-term biological interaction (symbiosis) in which members of one species gain benefits while those of the other species neither benefit nor are harmed. This is in contrast with mutualism (biology), mutualism, in which both o ...

with the human body. Intestinal microbiota also benefit the human

host A host is a person responsible for guests at an event or for providing hospitality during it. Host may also refer to: Places * Host, Pennsylvania, a village in Berks County People *Jim Host (born 1937), American businessman * Michel Host ...

, modulating essential metabolism-related processes within the gut microenvironment. '' P. distasonis and P. goldsteinii'' in particular form

biofilms A biofilm comprises any syntrophic consortium of microorganisms in which cells stick to each other and often also to a surface. These adherent cells become embedded within a slimy extracellular matrix that is composed of extracellular ...

in the

, allowing these species to survive under harsh conditions and maintain ample populations in extreme pH environments. Recent studies elucidate new applications of ''Parabacteroides'' as

probiotics Probiotics are live microorganisms promoted with claims that they provide health benefits when consumed, generally by improving or restoring the gut microbiota. Probiotics are considered generally safe to consume, but may cause bacteria-host i ...

, supporting balanced microbiota composition as a benefit to human digestive health. Both '' P. distasonis'' and '' P. goldsteinii'' exhibit anti-obesity effects via production of secondary

bile acids Bile acids are steroid acids found predominantly in the bile of mammals and other vertebrates. Diverse bile acids are synthesized in the liver. Bile acids are conjugated with taurine or glycine residues to give anions called bile salts. Primary b ...

and

succinate Succinic acid () is a dicarboxylic acid with the chemical formula (CH2)2(CO2H)2. The name derives from Latin ''succinum'', meaning amber. In living organisms, succinic acid takes the form of an anion, succinate, which has multiple biological ro ...

within the gut microenvironment. Studies on ''Parabacteroides'' species '' P. distasonis'' reveal metabolic benefits of this mechanism, including control of weight gain, decrease in

hyperglycemia Hyperglycemia is a condition in which an excessive amount of glucose circulates in the blood plasma. This is generally a blood sugar level higher than 11.1 mmol/L (200 mg/dL), but symptoms may not start to become noticeable until even ...

, and amelioration of

hepatic steatosis Fatty liver disease (FLD), also known as hepatic steatosis, is a condition where excess fat builds up in the liver. Often there are no or few symptoms. Occasionally there may be tiredness or pain in the upper right side of the abdomen. Complicat ...

and other metabolic diseases.

Taxonomy

Genomics

Species

Role in the human gut microenvironment

References

Further reading