Tetracycline hypersensitivity of an ezrA mutant links GalE and TseB (YpmB) to cell division.

Pamela Gamba,Leendert W Hamoen,Richard A Daniel,Eva Rietkötter

doi:10.3389/fmicb.2015.00346

Pamela Gamba, Leendert W Hamoen + Show 2 more

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https://doi.org/10.3389/fmicb.2015.00346

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Abstract

Cell division in bacteria is initiated by the polymerization of FtsZ into a ring-like structure at midcell that functions as a scaffold for the other cell division proteins. In Bacillus subtilis, the conserved cell division protein EzrA is involved in modulation of Z-ring formation and coordination of septal peptidoglycan synthesis. Here, we show that an ezrA mutant is hypersensitive to tetracycline, even when the tetracycline efflux pump TetA is present. This effect is not related to the protein translation inhibiting activity of tetracycline. Overexpression of FtsL suppresses this phenotype, which appears to be related to the intrinsic low FtsL levels in an ezrA mutant background. A transposon screen indicated that the tetracycline effect can also be suppressed by overproduction of the cell division protein ZapA. In addition, tetracycline sensitivity could be suppressed by transposon insertions in galE and the unknown gene ypmB, which was renamed tseB (tetracycline sensitivity suppressor of ezrA). GalE is an epimerase using UDP-glucose and UDP-N-acetylglucosamine as substrate. Deletion of this protein bypasses the synthetic lethality of zapA ezrA and sepF ezrA double mutations, indicating that GalE influences cell division. The transmembrane protein TseB contains an extracytoplasmic peptidase domain, and a GFP fusion shows that the protein is enriched at cell division sites. A tseB deletion causes a shorter cell phenotype, indicating that TseB plays a role in cell division. Why a deletion of ezrA renders B. subtilis cells hypersensitive for tetracycline remains unclear. We speculate that this phenomenon is related to the tendency of tetracycline analogs to accumulate into the lipid bilayer, which may destabilize certain membrane proteins.

Highlights

Division of a bacterial cell involves the coordinated action of several proteins that localize at midcell and assemble in a multiprotein complex known as the divisome
We show that overexpression of FtsL can suppress the tetracycline effect, and low levels of this key cell division regulator might be the reason for the phenotype
Using an extensive transposon screen we identified two new genes, galE and ypmB, which suppress the tetracycline sensitivity of an ezrA mutant when deleted

Summary

Introduction

Division of a bacterial cell involves the coordinated action of several proteins that localize at midcell and assemble in a multiprotein complex known as the divisome. Suppression of an ezrA mutation (Gueiros-Filho and Losick, 2002; Singh et al, 2008; Gundogdu et al, 2011; Pacheco-Gomez et al, 2013). Another conserved early cell division protein that binds to the Z-ring is EzrA, which will be discussed below. The transmembrane proteins PBP 2B, FtsL, DivIB, and DivIC are interdependent for their recruitment to the Z-ring. The exact function of FtsL, DivIB, and DivIC is unclear. DivIB might have a role in the regulation of FtsL and DivIC stability (Daniel et al, 2006)

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