The outer membrane permeability mutation of the virulence-associated plasmid of Salmonella typhimurium is located in a traT-like gene

Abstract

The SS‐A mutation carried by the virulence‐as‐associated plasmid of Salmonella typhimurium results in increased outer membrane permeability to hydrophobic compounds. A 7.8‐kilobase pair BamHI‐SalI fragment containing the SS‐A mutation was cloned from the virulence‐associated plasmid into the cloning vector pACYC184. The cloned DNA segment hybridized with a radioactive probed prepared from the traT gene of R6‐5. A similar DNA fragment, cloned from the wild‐type virulence‐associated plasmid, complemented the SS‐A mutant phenotype. Both clones produced a protein that immunologically resembled the R6‐5 TraT protein; however, the protein produced by the SS‐A containing clone appeared truncated by approximately Mr 1000 indicating an alteration in the primary structure or processing of the protein. We conclude that the mutation producing the SS‐A phenotype has occured in a traT‐like gene of the Salmonella plasmid.

Salicylidene Acylhydrazides That Affect Type III Protein Secretion inSalmonella entericaSerovar Typhimurium

“…To separate cytoplasmic membrane-associated proteins from the cell wall-associated fraction, the samples were vigorously suspended in 20 mM Tris-HCl, 5 mM MgCl 2 , and 1% (vol/vol) Triton X-100 buffer, pH 7.5. This procedure allowed us to make a crude fractionation of the bacterial cell into a cytoplasmic Triton X-100-soluble fraction and into a fraction not soluble in a neutral detergent (41).…”

Muramyl endopeptidase Spr contributes to intrinsic vancomycin resistance inSalmonella entericaserovar Typhimurium

“…Lipopolysaccharide (LPS) strongly contributes to this outer membrane integrity and mutations in genes involved in LPS biosynthesis, including envA, rfaC (waaC), and rfaP (waaP), sensitize Gram-negative bacteria simultaneously to numerous antimicrobials (Grundström, Normark, and Magnusson 1980;Helander et al 1989). Outer membrane integrity can also be disturbed by the expression of aberrant outer membrane proteins (Rhen, O'Connor, and Sukupolvi 1988), by exposing bacteria to polymyxin B nonapetide (Vaara and Vaara 1983;Ofek et al 1994), a compound which lacks intrinsic bacteriocidal activity, or by a simultaneous genetic depletion of several murein hydrolases (Heidrich et al 2002).…”

TraT lipoprotein, a plasmid-specified mediator of interactions between gram-negative bacteria and their environment.

“…Overproduction of TraT from strong vector promoters, however, may be deleterious for cell growth (66). The presence of a mutant TraT protein can increase the permeability of the outer membrane to hydrophobic compounds (76,86). This was first shown by introducing short (linker) insertion mutations in the traT gene of R6-5 (86), cloned in a repressible vector system (66).…”