Fig. 9: A schematic representation of the role of comK in S. aureus.

A comK induction in S. aureus laboratory cultures. comK expression is not required during the exponential growth of WT cells in TSB medium as carbohydrates are largely available for fermentative growth and when these carbohydrates become more scarce, S. aureus relies on respiration to obtain energy. The addition of H₂O₂ to the cultures inhibits S. aureus respiration; thus, cells grow using fermentation even when the concentration of carbohydrates decreases. In these growth conditions, the cells induce comK expression to increase their glycolytic capabilities. B comK induction during infection. S. aureus has little access to oxygen, and bacterial respiration is damaged by the ROS produced by the cells from the immune system (e.g. macrophages and/or neutrophils); respiration rates are therefore reduced. comK is induced by the presence of ROS via activation of AgrCA, SaeRS or SrrAB signaling pathways. comK induction is critical in cells that are unable to respire, to increase glucose and DNA uptake capabilities and to increase the glycolytic rate that allows and effective fermentative growth. DNA uptake provides an additional source of nucleotides required for the repair of DNA damage caused by ROS and a source of genetic material for horizontal gene transfer.