''Parabacteroides'' is a

Gram-negative Gram-negative bacteria are bacteria that, unlike gram-positive bacteria, do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. Their defining characteristic is that their cell envelope consists ...

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: *Adhesive#Anaerobic, Anaerobic ad ...

, non-

spore In biology, a spore is a unit of sexual reproduction, sexual (in fungi) or asexual reproduction that may be adapted for biological dispersal, dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores fo ...

-forming genus from the family ''

Tannerellaceae Tannerellaceae is a family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Idea ...

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

(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 g ...

along the digestive tract.

Taxonomy

The

taxon In biology, a taxon (back-formation from ''taxonomy''; : 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 name and ...

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 image:Hierarchical clustering diagram.png, 280px, Generalized scheme of taxonomy Taxonomy is a practi ...

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 DNA ...

) 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, re ...

, 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, mutualistic, or pathogenic found in and on all multicellular organisms, including plants. Microbiota include bacteria, archaea, protists, fungi, and viruses, and have been found ...

along the

digestive tract The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the Digestion, digestive system that leads from the mouth to the anus. The tract is the largest of the body's systems, after the cardiovascula ...

, benefitting from a commensal relationship 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 * Host Island, in the Wilhelm Archipelago, Antarctica People * ...

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

biofilms A biofilm is a syntrophic community 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 polymer ...

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 that provide health benefits when consumed, generally by improving or restoring the microbiota in the Gut microbiota, gut. Probiotics are considered GRAS, generally safe to consume, but may cause bacteria– ...

, 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 in peroxisomes. Bile acids are conjugated with taurine or glycine residues to give anions called bile ...

and

succinate Succinic acid () is a dicarboxylic acid with the chemical formula (CH2)2(CO2H)2. In living organisms, succinic acid takes the form of an anion, succinate, which has multiple biological roles as a metabolic intermediate being converted into Fuma ...

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 where unusually high amount of glucose is present in blood. It is defined as blood glucose level exceeding 6.9 mmol/L (125 mg/dL) after fasting for 8 hours or 10 mmol/L (180 mg/dL) 2 hours after eating. Blood gluc ...

, and amelioration of

hepatic steatosis Fatty liver disease (FLD), also known as hepatic steatosis and steatotic liver disease (SLD), 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 r ...

and other metabolic diseases.

Taxonomy

Genomics

Species

Role in the human gut microenvironment

References

Further reading