SanA Plays a Role in Peptidoglycan Integrity in Escherichia coli

Peptidoglycan synthesis and degradation are both essential for bacterial growth, and damaged peptidoglycan must be continuously repaired. In Escherichia coli, peptidoglycan required for cell elongation is synthesized by the Rod complex. Although RodZ is a non-essential component of this complex, its dysfunction leads to aberrant peptidoglycan synthesis, resulting in defects in cell shape and impaired growth. We previously isolated several suppressor mutants that restore growth in cells with impaired RodZ function (RMR cells). Most suppressor mutations mapped to components in the Rod complex other than RodZ. However, one suppressor mutation was identified in sanA, a gene not previously associated with the Rod complex. This mutation, sanA^M27R, represents a loss-of-function allele. Here, we show that SanA is associated with PBP1B, a non-essential yet physiologically important peptidoglycan synthase. Loss of SanA function partially restored the growth of RMR cells, accompanied by enhanced peptidoglycan synthesis and alleviation of structural defects in the cell wall. These findings indicate that SanA contributes to the regulation of peptidoglycan synthesis and cell wall integrity, potentially through functional interplay with PBP1B-dependent pathways.