Affiliation:
1. Department of Biology, Virginia Tech, Blacksburg, Virginia 24061
Abstract
ABSTRACT
The peptidoglycan cell wall determines the shape and structural integrity of a bacterial cell. Class B penicillin-binding proteins (PBPs) carry a transpeptidase activity that cross-links peptidoglycan strands via their peptide side chains, and some of these proteins are directly involved in cell shape determination. No
Bacillus subtilis
PBP with a clear role in rod shape maintenance has been identified. However, previous studies showed that during outgrowth of
pbpA
mutant spores, the cells grew in an ovoid shape for several hours before they recovered and took on a normal rod shape. It was postulated that another PBP, expressed later during outgrowth, was able to compensate for the lack of the
pbpA
product, PBP2a, and to guide the formation of a rod shape. The
B. subtilis pbpH
(
ykuA
) gene product is predicted to be a class B PBP with greatest sequence similarity to PBP2a. We found that a
pbpH-lacZ
fusion was expressed at very low levels in early log phase and increased in late log phase. A
pbpH
null mutant was indistinguishable from the wild-type, but a
pbpA pbpH
double mutant was nonviable. When
pbpH
was placed under the control of an inducible promoter in a
pbpA
mutant, viability was dependent on
pbpH
expression. Growth of this strain in the absence of inducer resulted in conversion of the cells from rods to ovoid/round shapes and lysis. We conclude that PBP2a and PbpH play redundant roles in formation of a rod-shaped peptidoglycan cell wall.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
66 articles.
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