Classification: Higher Order Taxa: Cellular Organisms; Bacteria; Terrabacteria group; Firmicutes; Negativicutes; Veillonellales; Veillonellaceae Species: Veillonella atypica
Description and Significance: Veillonella atypica is a gram-negative, strictly anaerobic, cocci-shaped bacterium. It is found in the intestines and the oral mucosa or mammals. Veillonella atypica in conjunction with Streptococcus spp, are known to be early colonizers in oral biofilm formation. V. atypica has also been noted to affect the formation of dental plaques. It is known for its ability to ferment lactate, converting it into propionate and acetate (2).
V. atypica isolates are commonly found in human oral cavities, where they make up substantial portions of the oral flora found in supra and subgingival dental plaque as well as on the oral mucosa. Veillonellae is also one of the most common bacteria present in saliva and dental plaque. The high prevalence and abundance of these species in the human oral cavity reflect their important position in the oral biofilm microbial community. V. atypica is considered a bridge species because it can co-aggregate/co-adhere with multiple other species and stimulate the growth of a wide range of organisms through metabolic complementation. Due to its unique preference for organic acid carbon sources, Veillonella atypica most likely plays a key role in the removal of harmful organic acid metabolic waste products from biofilm populations (3).
Genome Structure: Currently, the only complete V. atypica genome is that of V. atypica OK5, a human oral cavity isolate. V. atypica OK5 has a genome of 2.07 Megabases with a 39.1% GC content and 1790 predicted encoded proteins. Partial genomes and scaffolds of eight additional V. atypica isolates were subjected to a pan genome analysis, which revealed several themes. Most V. atypica isolates have the potential to synthesize carbohydrates such as chitin and cellulose. This bacteria is also able to synthesize the antibiotic avilamycin A. A large diversity among genomes of varying strains of V. atypica is indication of diverse carbohydrate metabolism among strains (4).
Cell Structure and Arrangement
V. atypica are Gram-negative anaerobic cells that appear spherical, kidney-shaped, and cocci-shaped. The cells occur in masses and short chains when subject to light microscopy. Their diameter ranges from 0.3μm to 0.5μm. V. atypica appears non-hemolytic on blood agar and is a non-motile organism (5).
Metabolism Veillonella species are anaerobic chemoorganotrophs. However, they do not ferment carbohydrates. Instead, they metabolize the organic acid by-products of fermentation processes, including lactate, pyruvate, malate, and fumarate. Lactate is a key source of energy, and it is converted to propionic acid and acetic acid, releasing CO2 and H2O in the process. Carbohydrates are not fermented. Growth necessitates CO2, but the nutritional requirements are complex and require further research (4).
Environment: V. atypica are usually found within the oral cavities, intestinal, and respiratory tracts of humans and animals (5).
Application to BioTech: V. atypica has been shown to improve treadmill run time in mice, which has generated interest in the potential to develop this finding into an application to enhance athletic performance. The presence of antibiotic synthesis clusters suggests that V. atypica can be used for its biosynthetic potential in making drugs. Extensive CRISPR-Cas arrays further suggest the potential to use V. atypica in genetic engineering (4).
Pathology: Little is known about V. atypica’s biological and pathological potential within the human microbiome, even with their prevalence among said biome. Veillonella atypica is a pathogen that is rarely a concern. Serologically specific endotoxins (lipopolysaccharides) are produced by these cells, causing pyrogenicity and the Schwarzman syndrome in rabbits (5).
Current Research: In a 2015 study published by the Kostic lab at the Joslin Diabetes Center and Harvard Medical School, Veillonella atypica was identified as a “performance-enhancing microbe”. Researchers took daily stool samples from 15 athletes who ran in the 2015 Boston Marathon, and ran microbiome analysis every day for a week before the marathon, and then again daily for a week after the marathon. The analytical results were compared with those from fecal samples taken from sedentary individuals. This analysis showed that V. atypica increased in relative abundance post-marathon. Additional experiments showed that radiolabelled lactate injected into the tail veins of mice treated with V. atypica could cross the gut epithelial barrier into the gut lumen within minutes and thus be accessible to the bacterium, supporting the idea that Veillonella could boost exercise efficiency by serving as a lactate drain and improve physical endurance. When researchers tested this hypothesis by providing experimental mice with a strain of V. atypica isolated from one of the runners, the mice were able to run for 13% longer than the control mice, supporting the hypothesis (6). V. atypica bacteria feed on lactic acid, a compound that builds up within the body following exercise. V. atypica produces propionate, a compound that is being examined as an athletic performance aid, although increased research is needed. V. atypica is being envisioned as a potential probiotic supplement that would increase meaningful exercise leading to the prevention of chronic diseases such as diabetes (7-9).
This photomicrograph indicates the presence of numerous gram-negative Veillonella species bacteria. (9)
References by appearance:
(2) Mashima, I., & Nakazawa, F. (2014). The influence of oral Veillonella species on biofilms formed by Streptococcus species. Anaerobe, 28, 54–61. https://doi.org/10.1016/j.anaerobe.2014.05.003
(3) Zhou, P., Liu, J., Merritt, J., & Qi, F. (2015). A YadA-like autotransporter, Hag1 in Veillonella atypica is a multivalent hemagglutinin involved in adherence to oral streptococci, Porphyromonas gingivalis, and human oral buccal cells. Molecular Oral Microbiology, 30(4), 269–279. https://doi.org/10.1111/omi.12091
(4) Han, M., Liu, G., Chen, Y., Wang, D., & Zhang, Y. (2020). Comparative Genomics Uncovers the Genetic Diversity and Characters of Veillonella atypica and Provides Insights Into Its Potential Applications. Frontiers in Microbiology, 11. https://doi.org/10.3389/fmicb.2020.01219
(5) Bergey, D. H., & Holt, J. G. (2000). Bergey's manual of determinative bacteriology. Lippincott Williams & Wilkins.
(6) Scheiman, J., Luber, J.M., Chavkin, T.A. et al. (2019) Meta-omics analysis of elite athletes identifies a performance-enhancing microbe that functions via lactate metabolism. Nat Med 25, 1104–1109. https://doi.org/10.1038/s41591-019-0485-4
(7) Ktori, S. (2019, June 25). Microbiomes of elite ATHLETES CONTAIN Performance-Enhancing Bacteria. https://www.genengnews.com/news/microbiomes-of-elite-athletes-contain-performance-enhancing-bacteria/.
(8) Joslin Diabetes. (n.d.). Performance-enhancing bacteria found in the microbiomes of elite athletes. EurekAlert! https://www.eurekalert.org/pub_releases/2019-06/jdc-pbf061919.php.
(9) What are intestinal bacteria that boost athletes' endurance? (n.d.). https://gigazine.net/gsc_news/en/20190629-athletes-performance-enhancing-bacteria/.