Table 1.

Some osmoprotectant systems detected in P. acnes.

Osmoprotectant	Comment
Aquaglyceroporin/glycerol uptake facilitator	Adjacent glycerol kinase suggests role of glycerol as a carbon and energy source, but glycerol-3-phosphate dehydrogenase is not in same operon.
Glycine betaine/L-proline three component ABC transporter (uptake system)	P. acnes can synthesise proline but not betaines or ectoine.
Trehalose synthesis	Different pathways in different strains, for example, from maltose, possibly from glycogen stores.
Osmosensitive potassium channel	Six genes; products mediate signal transduction in response to changes in turgor pressure.
Small conductance mechanosensitive ion channel Large conductance mechanosensitive ion channel	Responsive to membrane stretch such as that induced by increased turgor pressure inside the cell; small one close to glycerol uptake facilitator.
OsmC (peroxiredoxin)	Close to glycerol uptake facilitator; typically induced in late exponential phase. Strongly deregulated in P. acnes.