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J. Bacteriol., Aug 1995, 4303-4310, Vol 177, No. 15
KG Payie, PN Rather and AJ Clarke
A collection of Providencia stuartii mutants which either underexpress or
overexpress aac(2')-Ia, the chromosomal gene coding for gentamicin
2'-N-acetyltransferase (EC 2.3.1.59), have been characterized
phenotypically as possessing either lower or higher levels of peptidoglycan
O acetylation, respectively, than the wild type. These mutants were
subjected to both negative-staining and thin-section electron microscopy.
P. stuartii PR100, with 42% O acetylation of peptidoglycan compared with
52% O acetylation in the wild type, appeared as irregular rods. In direct
contrast, P. stuartii strains PR50.LM3 and PR51, with increased levels of
peptidoglycan O acetylation (65 and 63%, respectively), appeared as
coccobacilli and chain formers, respectively. Membrane blebbing was also
observed with the chain- forming strain PR51. Thin sectioning of this
mutant indicated that it was capable of proper constriction and separation.
P. stuartii PM1, when grown to mid-exponential phase, did not have altered
peptidoglycan O-acetylation levels, and cellular morphology remained
similar to that of wild-type strains. However, continued growth into
stationary phase resulted in a 15% increase in peptidoglycan O acetylation
concomitant with a change of some cells from a rod-shaped to a
coccobacillus-shaped morphology. The fact that these apparent morphological
changes were directly related to levels of O acetylation support the view
that this modification plays a role in the maintenance of peptidoglycan
structure, presumably through the control of autolytic activity.
Copyright © 1995, American Society for Microbiology
Contribution of gentamicin 2'-N-acetyltransferase to the O acetylation of peptidoglycan in Providencia stuartii
Department of Microbiology, University of Guelph, Ontario, Canada.
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