ABSTRACT
FtsZ, a protein essential for prokaryotic cell division, forms a ring structure known as the Z-ring at the division site. FtsZ has a GTP binding site and is assembled into linear structures in a GTP-dependent manner in vitro. We assessed whether guanosine 5'-diphosphate 3'-diphosphate (ppGpp), a global regulator of gene expression in starved bacteria, affects cell division in Salmonella Paratyphi A. Elevation of intracellular ppGpp levels by using the relA expression vector induced repression of bacterial growth and incorrect FtsZ assembly. We found that FtsZ forms helical structures in the presence of ppGpp by using the GTP binding site; however, ppGpp levels required to form helical structures were at least 20-fold higher than the required GTP levels in vitro. Furthermore, once formed, helical structures did not change to the straight form even after GTP addition. Our data indicate that elevation of the ppGpp level leads to inhibition of bacterial growth and interferes with FtsZ assembly.
Subject(s)
Bacterial Proteins/chemistry , Bacterial Proteins/metabolism , Cytoskeletal Proteins/chemistry , Cytoskeletal Proteins/metabolism , Guanosine Tetraphosphate/metabolism , Salmonella paratyphi A/growth & development , Arabinose/pharmacology , Bacterial Proteins/genetics , Bacterial Proteins/isolation & purification , Binding Sites , Cell Division , Cytoskeletal Proteins/genetics , Cytoskeletal Proteins/isolation & purification , Genetic Vectors , Guanosine Tetraphosphate/genetics , Guanosine Triphosphate/metabolism , Guanosine Triphosphate/pharmacology , Protein Binding , Salmonella paratyphi A/drug effects , Salmonella paratyphi A/genetics , Salmonella paratyphi A/ultrastructureSubject(s)
Salmonella paratyphi A/pathogenicity , Salmonella paratyphi A/ultrastructure , Salmonella paratyphi B/pathogenicity , Salmonella paratyphi B/ultrastructure , Salmonella paratyphi C/pathogenicity , Salmonella paratyphi C/ultrastructure , Salmonella typhi/classification , Salmonella typhi/pathogenicity , Salmonella typhi/ultrastructure , Typhoid Fever , Diagnosis, Differential , Paratyphoid Fever , Typhoid-Paratyphoid VaccinesABSTRACT
A spontaneous one-step mutant of Salmonella paratyphi A selected on ampicillin showed cross-resistance to all beta-lactam antibiotics except imipenem and to aminoglycosides, chloramphenicol, tetracycline, trimethoprim, and quinolones. It also grew as small colonies. Examination of the cell envelope of the mutant showed a quantitative decrease in three major outer membrane proteins of 40.6, 39.6 (presumably porins), and 24 kilodaltons and quantitative as well as qualitative modifications in the ladder pattern of lipopolysaccharide. Direct evidence for decreased permeability in the mutant included reduced uptake of [3H]glucose and norfloxacin, reduced accessibility of aztreonam and benzylpenicillin to penicillin-binding proteins in whole cells, and decreased diffusion of lactose and cephaloridine into proteoliposomes that were reconstituted with outer membrane proteins from the mutant. There was also loss of invasiveness of the mutant into HeLa cells. We assume that a pleiotropic mutation was responsible for multiple alterations in the outer membrane components of the resistant mutant of S. paratyphi A.
