Quorum sensing in the opportunistic pathogen Pseudomonas aeruginosa regulates N2O reduction

Through a process called denitrification, bacteria can respire with the use of as terminal electron acceptors instead of oxygen. An intermediate of the denitrification process, nitrous oxide (N2O), often escapes to the atmosphere instead of being reduced to N2. With properties such as being a potent greenhouse gas and ozone destructor, N2O has gained a lot of interest. The biggest anthropogenic N2O emission comes from agriculture, especially with the use of N-fertilizers. With the rise of global food demand, agriculture is becoming more and more important, which is also true for the use of N-fertilizer. Understanding denitrification will lead to knowledge of how to reduce N2O emission. Enter Pseudomonas aeruginosa, a well-studied model organism with a full denitrification apparatus: the bacterium contains genes encoding all factors necessary for the complete reduction of nitrate. This bacterium is also the leading cause of high mortality rate infections in hospitals. Gas kinetics performed in this study implies that mutating rhlI and lasI in P. aeruginosa severely reduces the accumulation of N2O during denitrification. Also, ddPCR performed in this study gives data on the transcriptional levels of nitrous oxide reductase (NosZ) during denitrification between a wildtype (PAO1) and the -rhlI -lasI mutant to determine the level of regulation at a transcriptional level. The hypothesis is that disabling the RhlI and LasI quorum sensing systems will remove the down regulation of nosZ transcription, which will lead to earlier and higher expression of nosZ. Furthering our understanding of how these quorum sensing systems impact N2O emissions can better equip us in a foreseeable future. A future of increased N2O emission following an increase in food demand and consequently agriculture and the usage of N-fertilizers across the world