What is "propionibacterium"

n. (context biology English) Any of various saprophytic gram-positive bacterium, of the genus (taxlink Propionibacterium genus noshow=1), that occur in milk and in the intestines, some of which are pathogenic, but others of which produce the holes in Swiss cheese

Propionibacterium is a Gram-positive, rod-shaped genus of bacteria named for their unique metabolism: They are able to synthesize propionic acid by using unusual transcarboxylase enzymes.

Its members are primarily facultative parasites and commensals of humans and other animals, living in and around the sweat glands, sebaceous glands, and other areas of the skin. They are virtually ubiquitous and do not cause problems for most people, but propionibacteria have been implicated in acne and other skin conditions. One study found the Propionibacterium was the most prevalent human skin-associated genus of microorganisms.

Members of the genus Propionibacterium are widely used in the production of vitamin B, tetrapyrrole compounds, and propionic acid, as well as in the probiotics and cheese industries.

The strain Propionibacterium freudenreichii subsp. shermanii is used in cheesemaking to create CO bubbles that become " eyes"—round holes in the cheese.