The active repertoire of Escherichia coli peptidoglycan amidases varies with physiochemical environment. Issue 1 (3rd April 2021)

• Record Type: Journal Article
• Authors: Mueller, Elizabeth A.; Iken, Abbygail G.; Ali Öztürk, Mehmet; Winkle, Matthias; Schmitz, Mirko; Vollmer, Waldemar; Di Ventura, Barbara; Levin, Petra Anne
• Is Part Of: Molecular microbiology. Volume 116:Issue 1(2021)
• Page Start: 311
• Page End: 328
• Publication Date: 2021-04-03
• Subjects: amidases -- cytokinesis -- morphogenesis -- peptidoglycan -- pH; Molecular microbiology -- Periodicals; 572.829
• DOI: 10.1111/mmi.14711
• Languages: English
• ISSNs: 0950-382X

Abstract

Abstract: Nearly all bacteria are encased in peptidoglycan, an extracytoplasmic matrix of polysaccharide strands crosslinked through short peptide stems. In the Gram‐negative model organism Escherichia coli, more than 40 synthases and autolysins coordinate the growth and division of the peptidoglycan sacculus in the periplasm. The precise contribution of many of these enzymes to peptidoglycan metabolism remains unclear due to significant apparent redundancy, particularly among the autolysins. E. coli produces three major LytC‐type‐ N ‐acetylmuramoyl‐ L ‐alanine amidases, which share a role in separating the newly formed daughter cells during cytokinesis. Here, we reveal two of the three amidases that exhibit growth medium‐dependent changes in activity. Specifically, we report acidic growth conditions stimulate AmiB—and to a lesser extent, AmiC—amidase activity. Combining genetic, biochemical, and computational analyses, we demonstrate that low pH‐dependent stimulation of AmiB is mediated through the periplasmic amidase activators NlpD, EnvC, and ActS (formerly known as YgeR). Although NlpD and EnvC promote amidase activity across pH environments, ActS preferentially stimulates AmiB activity in acidic conditions. Altogether, our findings support partially overlapping roles for E. coli amidases and their regulators in cell separation and illuminate the physiochemical environment as an important mediator of cell wall enzyme activity. Abstract : Escherichia coli produces three semi‐redundant peptidoglycan amidases involved in cell separation during cytokinesis. Here, we report that two of these amidases, AmiB and AmiC, have enhanced activity in acidic medium. Low pH‐dependent AmiB stimulation requires two known amidase activators, EnvC and NlpD, as well as the previously unknown amidase activator ActS. These findings reveal a previously unappreciated role for the growth environment in regulating the active repertoire of extracellular cell wall enzymes and modulatory factors.