Firmicutes, Low-G+C Gram positive species most often spore-forming, in two/three classes: the class Bacilli such as the Bacillus spp. (e.g. B. anthracis, a pathogen, and B. subtilis, biotechnologically useful), lactic acid bacteria (e.g. Lactobacillus casei in yoghurt, Oenococcus oeni in malolactic fermentation, Streptococcus pyogenes, pathogen), the class Clostridia of mostly anaerobic sulphite-reducing saprophytic species, includes the genus Clostridium (e.g. the pathogens C. dificile, C. tetani, C. botulinum and the biotech C. acetobutylicum).

• PMID 16497592

• PMID 16033867

• doi:10.1001/jama.2016.20099

• PMID 17183309

In dogs gut, Firmicutes can aid in the sequestration of energy from carbohydrates. The abundance of Firmicutes are associated with obesity. Consuming high-calorie diets will stimulate growth of Firmicutes. A diet rich in carbohydrates may increase the number of Firmicutes in the dog gut microbiota.

• Million, M., Lagier, J.-C., Yahav, D. & Paul, M. Gut bacterial microbiota and obesity. Clin. Microbiol. Infect. 19, 305–313 (2013).

• Ley, R. E., Turnbaugh, P. J., Klein, S. & Gordon, J. I. Microbial ecology: human gut microbes associated with obesity. Nature 444, 1022–1023 (2006).

• Krajmalnik-Brown, R., Ilhan, Z.-E., Kang, D.-W. & DiBaise, J. K. Effects of gut microbes on nutrient absorption and energy regulation. Nutr. Clin. Pract. 27, 201–214 (2012).