Deletion of PBP1a/LpoA complex compromises cell envelope integrity in Shewanella oneidensis

Abstract

High molecular weight penicillin binding proteins (PBPs) are responsible for the biosynthesis of peptidoglycan. In Escherichia coli, PBP1a and PBP1b form multienzyme peptidoglycan-synthesizing complexes with outer-membrane lipoproteins LpoA and LpoB, respectively. The two complexes appear to be largely redundant, although their distinct physiological roles remain unclear. PBP1a/LpoA and PBP1b/LpoB also exist in Shewanella oneidensis strain MR-1, but effects of the two complexes on aerobic growth and β-lactam resistance are quite different. In this study, the phenotypes of strains lacking a certain complex in S. oneidensis were compared. Deletion of PBP1a/LpoA caused aberrant cell morphology (including branches and bulges), enhanced sensitivity to various envelope stresses and outer membrane permeability. On the contrary, strains lacking PBP1b/LpoB displayed phenotypes similar to the wild type.