A D , D ‐carboxypeptidase is required for V ibrio cholerae halotolerance

• Published in: Environmental microbiology Vol. 17; no. 2; pp. 527 - 540
• Main Authors: Möll, Andrea, Dörr, Tobias, Alvarez, Laura, Davis, Brigid M., Cava, Felipe, Waldor, Matthew K.
• Format: Journal Article
• Language: English
• Published: 01-02-2015
• ISSN: 1462-2912; 1462-2920
• DOI: 10.1111/1462-2920.12779

The biological roles of low molecular weight penicillin‐binding proteins (
LMW PBP
) have been difficult to discern in
G
ram‐negative organisms. In
E
scherichia coli
, mutants lacking these proteins often have no phenotype, and cells lacking all seven
LMW PBPs
remain viable. In contrast, we report here that
V
ibrio cholerae
lacking
DacA
‐1, a
PBP
5 homologue, displays slow growth, aberrant morphology and altered peptidoglycan (
PG
) homeostasis in Luria–Bertani (
LB
) medium, as well as a profound plating defect.
DacA
‐1 alone among
V
. cholerae's

LMW PBPs
is critical for bacterial growth; mutants lacking the related protein
DacA
‐2 and/or homologues of
PBP
4 or
PBP
7 displayed normal growth and morphology. Remarkably, the growth and morphology of the
dac
A
‐1
mutant were unimpaired in
LB
media containing reduced concentrations of
N
a
C
l (100 mM or less), and also within suckling mice, a model host for the study of cholera pathogenesis. Peptidoglycan from the
dac
A
‐1
mutant contained elevated pentapeptide levels in standard and low salt media, and comparative analyses suggest that
DacA
‐1 is
V
. cholerae's
principal
DD
‐carboxypeptidase. The basis for the
dac
A
‐1
mutant's halosensitivity is unknown; nonetheless, the mutant's survival in biochemically uncharacterized environments (such as the suckling mouse intestine) can be used as a reporter of low
N
a
+
content.