The active repertoire of Escherichia coli peptidoglycan amidases varies with physiochemical environment

Elizabeth A. Mueller, Abbygail G. Iken, Mehmet Ali Öztürk, Matthias Winkle, Mirko Schmitz, Waldemar Vollmer, Barbara Di Ventura, Petra Anne Levin

Research output: Contribution to journalArticlepeer-review

18 Scopus citations

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.

Original languageEnglish
Pages (from-to)311-328
Number of pages18
JournalMolecular Microbiology
Volume116
Issue number1
DOIs
StatePublished - Jul 2021

Keywords

  • amidases
  • cytokinesis
  • morphogenesis
  • pH
  • peptidoglycan

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