Veillonella

Veillonella are Gram-negative bacteria (Gram stain pink) anaerobic cocci, unlike most Bacillota, which are Gram-positive bacteria. This bacterium is well known for its lactate fermenting abilities. It is a normal bacterium in the intestines and oral mucosa of mammals. In humans they have been implicated in cases of osteomyelitis and endocarditis, for example with the species Veillonella parvula.

Veillonella dispar is the most nitrate-reducing bacterium in the oral cavity, which is beneficially anti-bacterial.

When Veillonella is responsible for clinical infections in humans, it should be kept in mind that more than 70% of the strains are resistant to penicillin, while more than 95% of the strains are susceptible to amoxicillin/clavulanate.

Previous studies have shown that exercise is associated with changes in microbiome composition. Specifically, Veillonella, Bacteroides, Prevotella, Methanobrevibacter, and Akkermansiaceae are in more abundance in endurance athletes. Specifically, the study that is currently very briefly introduced in the Wikipedia page has proposed that V. atypica is beneficial for endurance performance because the high-lactate environment of the athlete provides a selective advantage for colonization by lactate metabolizing organisms, such as Veillonella. Previous studies in mice have shown that propionate increases heart rate variability (HRV) and VO2 max. It also raises the resting energy expenditure and lipid oxidation in fasted humans. These modifications are beneficial for athletes because an increase in HRV indicates that the body is adapting to the exercise stimuli, indicating an increase in fitness. Also, a higher VO2 max allows the athlete to produce more energy which allows them to do more work and an increase in lipid oxidation delays the initiation of glycogen depletion.

Fermentation
Lactate is fermented to propionate and acetate by the methylmalonyl-CoA pathway. Little ATP is produced in this fermentation. High substrate affinity is suggested to be the reason.

3 Lactate → acetate + 2 propionate + +

A study of Veillonella in endurance athletes found that a relative abundance of the bacteria in the gut is associated with increased treadmill run time performance. This effect was demonstrated to be due to the organism's propionate metabolite produced from lactic acid.

Phylogeny
The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN) and National Center for Biotechnology Information (NCBI)

Unassigned species:
 * "V. agrestimuris" Afrizal et al. 2022
 * "Ca. V. atypica" Drancourt et al. 2004 non (Rogosa 1965) Mays et al. 1982
 * "V. fallax" Afrizal et al. 2022
 * "V. intestinalis" Afrizal et al. 2022
 * "V. massiliensis" Togo et al. 2017
 * "V. variabilis" Magrassi 1944

Infections and Treatment
Meningitis, osteomyelitis, periodontitis, and endocarditis are infections that can be caused by V. parvula.     Prosthetic joint infection and endocarditis have been shown to be caused by V. dispar. Although very rare, endocarditis has also been caused by V. montpellierensis and V. alcalescens.

A large percentage of Veillonella species are resistant to penicillin. Antibiotics that Veillonella species are less resistant to or not resistant to at all include clindamycin, metronidazole, imipenem, ceftriaxone, and amoxicillin.