The cell wall amidase AmiB is essential for Pseudomonas aeruginosa cell division, drug resistance and viability

Abstract

SUMMARY The physiological function of cell wall amidases has been investigated in several proteobacterial species. In all cases, they have been implicated in the cleavage of cell wall material synthesized by the cytokinetic ring. Although typically non-essential, this activity is critical for daughter cell separation and outer membrane invagination during division. In Escherichia coli, proteins with LytM domains also participate in cell separation by stimulating amidase activity. Here, we investigated the function of amidases and LytM proteins in the opportunistic pathogen Pseudomonas aeruginosa. In agreement with studies in other organisms, PaAmiB and three LytM proteins were found to play crucial roles in P. aeruginosa cell separation, envelope integrity, and antibiotic resistance. Importantly, the phenotype of amidase-defective P. aeruginosa cells also differed in informative ways from the E. coli paradigm; PaAmiB was found to be essential for viability and the successful completion of cell constriction. Our results thus reveal a key role for amidase activity in cytokinetic ring contraction. Furthermore, we show that the essential function of PaAmiB can be bypassed in mutants activated for a Cpx-like envelope stress response, suggesting that this signaling system may elicit the repair of division machinery defects in addition to general envelope damage.

The SPOR Domain, a Widely Conserved Peptidoglycan Binding Domain That Targets Proteins to the Site of Cell Division

“…The appearance of denuded glycans in septal PG creates a positive-feedback loop that recruits additional FtsN and drives a burst of PG synthesis when and where it is needed (11). Consistent with this notion, synthesis of septal PG sometimes fails to reach completion in amidase mutants (16,54,55). Paradoxically, tethering FtsN to denuded glycans might also create a negative-feedback loop that prevents synthesis of septal PG from running too far ahead of the PG hydrolases.…”

Cell-wall recycling and synthesis in Escherichia coli and Pseudomonas aeruginosa – their role in the development of resistance

“…Both these proteins share homology with their E. coli counterparts and have N-acetylmuramyl-L-alanine amidase activity [137]. Deletion of amiA exhibited no significant effect on P. aeruginosa cell viability or morphology [138]. AmiB (PA4947) in contrast to E. coli AmiB was found to be essential for P. aeruginosa survival [138].…”

“…Deletion of amiA exhibited no significant effect on P. aeruginosa cell viability or morphology [138]. AmiB (PA4947) in contrast to E. coli AmiB was found to be essential for P. aeruginosa survival [138]. P. aeruginosa AmiB is required for cell separation during division, as depletion resulted in filamentous growth with a marked deficiency in the invagination of the inner membrane.…”

“…P. aeruginosa AmiB is required for cell separation during division, as depletion resulted in filamentous growth with a marked deficiency in the invagination of the inner membrane. Additionally, AmiB depletion decreased outer membrane impermeability for which the mechanism is unclear [138]. P. aeruginosa AmiB requires the presence of additional activator dLytM proteins such as NlpD, NlpS and EnvC [138].…”

“…Additionally, AmiB depletion decreased outer membrane impermeability for which the mechanism is unclear [138]. P. aeruginosa AmiB requires the presence of additional activator dLytM proteins such as NlpD, NlpS and EnvC [138].…”