Kg. Payie et al., CONTRIBUTION OF GENTAMICIN 2'-N-ACETYLTRANSFERASE TO THE O-ACETYLATION OF PEPTIDOGLYCAN IN PROVIDENCIA-STUARTII, Journal of bacteriology, 177(15), 1995, pp. 4303-4310
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 phenoty
pically as possessing either lower or higher levels of peptidoglycan O
acetylation, respectively, than the wild type. These mutants were sub
jected to both negative-staining and thin-section electron microscopy.
P. stuartii PR100, with 42% O acetylation of peptidoglycan compared w
ith 52% O acetylation in the wild type, appeared as irregular rods. In
direct contrast, P, stuartii strains PR50,LM3 and PR51, with increase
d levels of peptidoglycan O acetylation (65 and 63%, respectively), ap
peared as coccobacilli and chain formers, respectively. Membrane blebb
ing was also observed with the chain-forming strain PR51. Thin section
ing of this mutant indicated that it was capable of proper constrictio
n and separation, P. stuartii PM1, when grown to mild-exponential phas
e, did not have altered peptidoglycan O-acetylation levels, and cellul
ar morphology remained similar to that of wild-type strains. However,
continued growth into stationary phase resulted in a 15% increase in p
eptidoglycan O acetylation concomitant with a change of some cells fro
m a rod-shaped to a coccobacillus-shaped morphology. The fact that the
se apparent morphological changes were directly related to levels of O
acetylation support the view that this modification plays a role in t
he maintenance of peptidoglycan structure, presumably through the cont
rol of autolytic activity.