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Journal of Bacteriology, June 2009, p. 3526-3533, Vol. 191, No. 11
0021-9193/09/$08.00+0     doi:10.1128/JB.01812-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

In Escherichia coli, MreB and FtsZ Direct the Synthesis of Lateral Cell Wall via Independent Pathways That Require PBP 2{triangledown}

Archana Varma and Kevin D. Young*

Department of Microbiology and Immunology, University of North Dakota School of Medicine and Health Sciences, Grand Forks, North Dakota 58202-9037

Received 23 December 2008/ Accepted 23 March 2009

In Escherichia coli, the cytoplasmic proteins MreB and FtsZ play crucial roles in ensuring that new muropeptide subunits are inserted into the cell wall in a spatially correct way during elongation and division. In particular, to retain a constant diameter and overall shape, new material must be inserted into the wall uniformly around the cell's perimeter. Current thinking is that MreB accomplishes this feat through intermediary proteins that tether peptidoglycan synthases to the outer face of the inner membrane. We tested this idea in E. coli by using a DD-carboxypeptidase mutant that accumulates pentapeptides in its peptidoglycan, allowing us to visualize new muropeptide incorporation. Surprisingly, inhibiting MreB with the antibiotic A22 did not result in uneven insertion of new wall, although the cells bulged and lost their rod shapes. Instead, uneven (clustered) incorporation occurred only if MreB and FtsZ were inactivated simultaneously, providing the first evidence in E. coli that FtsZ can direct murein incorporation into the lateral cell wall independently of MreB. Inhibiting penicillin binding protein 2 (PBP 2) alone produced the same clustered phenotype, implying that MreB and FtsZ tether peptidoglycan synthases via a common mechanism that includes PBP 2. However, cell shape was determined only by the presence or absence of MreB and not by the even distribution of new wall material as directed by FtsZ.

* Corresponding author. Present address: Department of Microbiology and Immunology, University of Arkansas for Medical Sciences, Little Rock, AR 72205-7199. Phone: (501) 526-6802. Fax: (501) 686-5359. E-mail: kdyoung{at}uams.edu

{triangledown} Published ahead of print on 3 April 2009.

Journal of Bacteriology, June 2009, p. 3526-3533, Vol. 191, No. 11
0021-9193/09/$08.00+0     doi:10.1128/JB.01812-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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