THE ROLE OF O-ACETYLATION IN THE METABOLISM OF PEPTIDOGLYCAN IN PROVIDENCIA-STUARTII

The gentamicin 2'-N-acetyltransferase [EC 2.3.1.59; AAC(2')-Ia] of Pro videncia stuartii was shown to contribute to the O-acetylation of pept idoglycan and mutants that either under- or overexpress the aac(2')-Ia gene was characterized phenotypically to possess either lower or high er levels of peptidoglycan O-acetylation, respectively, compared to th e wild-type, These mutants were subjected to scanning electron microsc opy, P, stuartii PR100, with 42-44% peptidoglycan O-acetylation compar ed to 54% for the wild-type, appeared as irregular rods, In direct con trast, strains PR50.LM3 and PR51, with increased levels of peptidoglyc an O-acetylation (63 and 65%, respectively), appeared as coccobacilli or chain formers, respectively, Zymogram analysis of the autolysins pr oduced by another member of the closely related Proteeae group of bact eria, Proteus mirabilis, indicated the presence of three classes of en zymes: one that acts preferentially on native, O-acetylated peptidogly can, a second that hydrolyses non-O-acetylated peptidoglycan, and a th ird that is not distinguished by the two forms of substrate, Ou the ba sis of the apparent morphological changes directly related to levels o f O-acetylation combined with the presence of different classes of aut olysins, a model is proposed that invokes the role of this modificatio n in the control of autolysins for the maintenance of the structure of the peptidoglycan sacculus.