GSE185398
RpoN/Sfa2-dependent activation of the Pseudomonas aeruginosa H2-T6SS and its cognate arsenal of antibacterial toxins
Pseudomonas aeruginosa uses three type six secretion systems (H1-, H2- and H3-T6SS) to manipulate its environment, subvert host cells and compete with microbial competitors. These T6SS machines can be loaded with a variety of effectors/toxins, many being associated with a specific VgrG. How P. aeruginosa transcriptionally coordinates the three main T6SS clusters and the multiple vgrG islands spread through the genome is unknown. Here we show an unprecedented level of control of the regulator RsmA in repressing most known T6SS-related genes. Moreover, it is noticeable that a sigma factor activator (SFA) protein is encoded in each of H2- and H3-T6SS clusters, Sfa2 and Sfa3, respectively. SFA proteins are enhancer binding proteins that usually work in concert with the sigma factor RpoN. Using a combination of RNA-seq, ChIP-seq and molecular biology approaches, we demonstrate that RpoN coordinates the T6SSs of P. aeruginosa by activating the H2-T6SS but repressing the H1- and H3-T6SS. Furthermore, RpoN and Sfa2 control the expression of all H2-T6SS-linked VgrG and effector arsenal to enable very effective interbacterial killing. Such RpoN-dependent control is exerted both directly and indirectly. The function of the SFA protein is specific since the H3-T6SS associated Sfa3 cannot complement loss of Sfa2. Our study further delineates the multiple regulatory mechanisms that modulate the deployment of an arsenal of T6SS effectors likely to respond and adapt to a range of environmental conditions that a versatile organism like P. aeruginosa would encounter. Overall design: Five different samples (PA14, PA14rsmA, PA14rsmAsfa2, PA14rsmArpoN, PA14rsmAsfa2, PA14rsmAsfa3) with three replicate for each. Anaylsis perfromed against all samples but foucs of the study is the comparision against PA14rsmA.