Verrucomicrobia

Verrucomicrobia are Gram-negative, coccoid or rod-shaped bacteria with unusual cellular structure, featuring wart-like cellular protrusions and a unique compartmentalized cell plan. The plan challenges our concept of prokaryote cells because the few Verrucomicrobia cultured species have revealed them to have characteristics atypical of other bacteria.

Verrucomicrobia's oxygen requirement varies. The members are strict aerobes, facultative anaerobes or strict anaerobes. They are ubiquitous in a wide range of aquatic and terrestrial habitats. They were found not only at moderate temperatures but also at cold temperatures in the deep sea and in Antarctica. One species was isolated from a hot spring (75-90°C). Others have been found in extreme environments such as sulfide-rich water, a soda lake, and extremely low-pH environments.

Verrucomicrobia are a globally distributed, abundant, and active group of soil bacteria. However, in spite of being one of the most abundant bacterial groups present in soil, not much is known about their ecological importance or factors that affect their distribution and diversity in soil.

Verrucomicrobia species have also been identified in human gastrointestinal tract and even as ecto- and endosymbionts of eukaryotes. Recent studies suggest that Verrucomicrobium spinosum possesses a toxic protein that increases the mortality of its insect and worm hosts.1,2

Verrucomicrobia Species

Transmission electron micrograph of high-pressure frozen and cryosubstituted cell of Verrucomicrobium spinosum
Electron micrograph of high-pressure frozen and cryosubstituted cell of Verrucomicrobium spinosum

Verrucomicrobia are divided in three main classes: Opitutae, Spartobacteria, and Verrucomicrobiae. Most of the Verrucomicrobia isolates have been found to utilize carbohydrates for their energy needs. However, three very recent studies have shown members of this phylum to be involved in utilizing methane. Verrucomicrobia from a methane-emitting geothermal field in New Zealand, a Solfatara volcano mudpot in Italy, and from an acidic hot spring in Kamchatka, Russia, are capable of growing aerobically at 55-60°C with methane as the sole carbon source.

Another interesting aspect of Verrucomicrobia is their probable role in cellulose degradation. Preliminary analysis of the genome of the Verrucomicrobium spinosum has indicated its genomic capability to degrade cellulose. Degradation of cellulose to fermentable sugar is a major hindrance in the field of biofuel production.



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Verrucomicrobia are among the seven bacterial divisions that constitute the human gut microbiota. Akkermansia muciniphila is a strictly anaerobic bacterium, originally isolated from a human fecal sample, that can use gastric mucin (constituent of mucus) as carbon, energy and nitrogen source. It has been named after Dutch microbiologist Antoon D.L. Akkermans, professor at Wageningen University and a pioneer in studying molecular ecology of bacterial communities. Recent studies showed that A. muciniphila is a common inhabitant of the human intestinal tract, comprising up to 1% of the total bacteria in the intestine. It grows optimally at 37°C and is capable of fermenting glucose, N-acetylglucosamine and N-acetylgalactosamine 3. Mucus can serve as a barrier to protect the underlying epithelium from the attachment of pathogens and also as a source of nutrients for commensal bacteria. Degradation of mucin is regarded as a disease causing factor since loss of the protective mucus layer may expose gastrointestinal tract cells to pathogens 4.

(From: BMC Microbiol. 2009; 9: 5.)

References

  1. Martin Dworkin, Stanley Falkow. The Prokaryotes: A Handbook on the Biology of Bacteria: Vol. 7
  2. Genomic and Experimental Evidence Suggests that Verrucomicrobium spinosum Interacts with Eukaryotes
  3. New feel for new phyla
  4. Muriel Derrien, Elaine E. Vaughan, Caroline M. Plugge and Willem M. de Vos. Akkermansia muciniphila gen. nov., sp. nov., a human intestinal mucin-degrading bacterium
  5. Verrucomicrobia: A Model Phylum to study the Effects of Deforestation on Microbial Diversity in the Amazon Forest (uta.edu)
  6. Phylum Verrucomicrobia representatives share a compartmentalized cell plan with members of bacterial phylum Planctomycetes

 

 

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