Bacteroides plebeius

Classification

Domain: Bacteria

Phylum: Bacteroidetes

Class: Bacteroidia

Order: Bacteroidales

Family: Bacteroidaceae

Genus : Bacteroides

Species: plebeius

Species

Bacteroides plebeius

Description and Significance

Bacteroides plebeius is gram-negative, non-motile, Anaerobic, Bacilli-shaped bacteria found in the gut of certain human populations, specifically people of Japanese descent [1][2]. Notably, it has the ability to produce porphyranase, an enzyme that can break down porphyan, a complex carbohydrate found in red seaweed. The prevailing theory is that it received this ability via horizontal gene transfer from an aquatic microbe, Zobellia galactanivorans that was ingested by a human. Although this microbe was unable to colonize the gut, it is believed to have transferred its porphyranase-coding genes to B. plebeius through horizontal gene transfer while passing through the digestive system. [2]

Genome Structure

The median genome size of recorded B. plebeius strains is 4.42 Mb, with a median G/C% of 44.3. [1] B. plebeius contains a polysaccharide utilization locus (PUL) that is believed to originate from the marine bacterium Zobellia galactanivorans. Specifically, this PUL contains two genes, BACPLE_01689 and BACPLE_01693, that code for β-porphyranases, enzymes that can break down porphyran. [2]

Cell Structure, Metabolism, and Life Cycle

B. plebeius is a gram negative, rod-shaped, not-motile, non spore-forming bacteria. It has an average length of about 3 µm and an average width of about 0.8 µm. [4] B. plebeius sustains itself using porphyran as a substrate, which it does by producing porphyranase. [3] The bacteria break down porphyran and release volatile fatty acids that are then absorbed through the large intestine of the host.[5]

Ecology and Pathogenesis

Bacteroides are the most abundant microbes found in the intestines of mammals, existing in a mutualistic relationship with its host. However, they can become opportunistic pathogens if they are able to escape the gut. [1] This egress is often the result of the rupturing of the GI tract or due to intestinal surgery. [5] When acting as a pathogen, they can cause bacteremia and the formation of abcesses in various parts of the body such as the abdomen, brain, liver, pelvis, and lungs. [5] Bacteroides also have more antibiotic resistance mechanisms and higher antibiotic resistance rates compared to all other anaerobic pathogens. [5] Additionally, recent studies have shown a link between bacteroides and firmicutes populations and obesity in both humans and germ-free mice. [5] Many gut microbes, including B. plebeius, are able to produce carbohydrate active enzymes (CAZymes) that cannot be produced by the human genome, and thus exist in a symbiotic relationship with their human hosts. Marine algae contain sulphated polysaccharides, which are not found in terrestrial plants. B. plebeius can break down these sulphated polysaccharides, which allows the host to digest the broken-down VFAs released by the microbe after digestion of these polysaccharides.

References

[1] Bacteroides plebeius [Internet]. Bethesda (MD) : National Library of Medicine (US), National Center for Biotechnology Information; 2004 - {cited 2020 Apr 30]. Available from: https://www.ncbi.nlm.nih.gov/genome/?term=txid310297[Organism:exp]

[2] Hehemann et al 2012, ‘Bacteria of the human gut microbiome catabolize red seaweed glycans with carbohydrate-active enzyme updates from extrinsic microbes’, PNAS, vol. 109, no.48, pp. 19786-19791

[3] Hehemann, J., Correc, G., Barbeyron, T. et al. Transfer of carbohydrate-active enzymes from marine bacteria to Japanese gut microbiota. Nature 464, 908–912 (2010). https://doi-org.proxyiub.uits.iu.edu/10.1038/nature08937

[4] Bacteroides plebeius M12: Type strain: CCUG 54634, DSM 17135, JCM 12973: BacDiveID:1607. (n.d.). Retrieved April 30, 2020, from https://bacdive.dsmz.de/search?search=bacteroides+plebeius

[5] Wexler, H 2007, ‘Bacteroides: the Good, the Bad, and the Nitty-Gritty’, Clinical Microbiology Reviews, vol. 20, no.4, pp. 593-621.

[6] Kitahara, M., Sakamoto, M., Ike, M., Sakata, S., Benno, Y. 2005 ‘Bacteroides plebeius sp. nov. and Bacteroides coprocola sp. nov., isolated from human faeces’, Internation Journal of Systematic and Evolutionary Microbiology, vol. 55, no. 5, pp. 2143-2147

Author

Page authored by Ryan Curtiss, student of Prof. Jay Lennon at Indiana University