Social Behaviours under Anaerobic Conditions in Pseudomonas
aeruginosa
Figure 1
(a) Denitrification regulation in P. aeruginosa. Denitrification is regulated by physiochemical conditions, such as oxygen concentration and the availability of nitric oxides as well as cell-cell communication molecules. (b) Denitrification regulation by physiochemical factors in P. aeruginosa. ANR is activated under low-oxygen tension conditions, which increases the transcription of the NarXL two-component system and DNR. NarXL responds to nitrate and activates the expression of DNR together with ANR. DNR is activated in the presence of NO and induces the transcription of the four reductases. The narK1K2GHJI operon, which encodes nitrate/nitrite transporters and the structural gene for NAR, is also induced by ANR and NarL. (c) Denitrification regulation by cell-cell communication. C4-HSL and 3-o-C12-HSL repress the transcription of denitrifying reductases via their cognate receptors RhlR and LasR. Regulation by LasR is dependent on RhlR. PQS represses the activity of the NAR, NOR, and NOS enzymes while activating the NIR enzyme. PqsR and PqsE are involved in the PQS effect on NOR, while the effect on the other three enzymes does not require PqsR or PqsE.
