Genetic and physiological classification of periplasmic-leaky mutants of Salmonella typhimurium

132

Periplasmic-leaky mutants of Escherichia coli K-12 were isolated after nitrosoguanidine-induced mutagenesis. They released periplasmic enzymes into the extracellular medium. Excretion of alkaline phosphatase, which started immediately in the early exponential phase of growth, could reach up to 90% of the total enzyme production in the stationary phase. Leaky mutants were sensitive to ethylenediaminetetraacetic acid, cholic acid, and the antibiotics rifampin, chloramphenicol, mitomycin C, and ampicillin. Furthermore, they were resistant to colicin El and partially resistant to phage TuIa. Their genetic characterization showed that the Iky mutations mapped between the suc and gal markers, near or in the tolPAB locus. A biochemical analysis of cell envelope components showed that periplasmic-leaky mutants contained reduced amounts of major outer membrane protein OmpF and increased amounts of a 16,000-dalton outer membrane protein.

“…Sensitivity to drugs. Periplasmic-leaky mutants were tested for sensitivity to a variety of drugs known to inhibit growth of cell envelope mutants (10,33,39). Mutants 207c and 236c…”

Section: Sensitivity Of Periplasmic-leaky Mutants To Bacteriophages Amentioning

confidence: 99%

Genetic and biochemical characterization of periplasmic-leaky mutants of Escherichia coli K-12

Lazzaroni¹,

Portalier²

1981

132

“…4e). Sensitivity to DOC has been frequently found among cell envelope mutants isolated by several different procedures (6,18,26,28). It also appeared in this case and at very high frequency, since 24 of the 41 strains isolated demonstrated sensitivity to DOC ( Table 2).…”

mentioning

confidence: 64%

Positive selection of mutants with cell envelope defects of a Salmonells typhimurium strain hypersensitive to the products of genes hisF and hisH

Antón¹

1979

“…Strain RB338 was isolated as a recombinant between SA536 (Hfr, gal+) and R18 (F galE iky). Gal+ exconjugants were screened for nonleaky recombinants (37) and subsequently analyzed for expression of OM1, -2, and -3. Strain RB338 is constitutive for OM1, -2, and -3 but no longer leaks ribonuclease (37).…”

Section: Regulation Of Iron Uptake Systems 929mentioning

confidence: 99%

“…Gal+ exconjugants were screened for nonleaky recombinants (37) and subsequently analyzed for expression of OM1, -2, and -3. Strain RB338 is constitutive for OM1, -2, and -3 but no longer leaks ribonuclease (37). Strain RB181 was derived from R18 after mutagenesis with Nmethyl-N'-nitro-N-nitrosoguanidine.…”

Section: Regulation Of Iron Uptake Systems 929mentioning

confidence: 99%

See 1 more Smart Citation

Constitutive expression of the iron-enterochelin and ferrichrome uptake systems in a mutant strain of Salmonella typhimurium

Ernst¹,

Bennett²,

Rothfield³

1978

Self Cite

160

Two hih-affinity iron uptake systems are known in Salmonella typhunurinum, one utiig iron-enteohelin and the other uliing ferichrome. It has been shown previously that expreon of several element of the iron-enterochelin uptake system are ated by the iron content of the medium, with growth in high-iron medium resulting in repon of enzymes of enterochelin synthsis and degradation and of the ability of whole cels to take up iron-enterochelin In this study we describe a mutant strain in which growth in high-iron medium was assciated with constitutive exreon of. (i) iron-enterochelin uptake by whole cells (ii) ferirome uptake by whole cells; (iii) synthesis of enterochelin; (iv) itracellular degradation of iron-enterochelin; and (v) synthesis of three major outer-membe prot (OM1, OM2, and OM3). In conbwtr in the wildtype strain the4s prorties were only after growth in iron-deficient medium. It is proposed that the mutation ffects a gene responsible for regulating expssion of the structual genes for the components of the high-affinity iron uptake ystems. The term fur, for iron (Fe) uptake regulation, is suggetd for this new class of mutant. Several high-affinity systems are known to perticipate in iron uptake in SabnoneUa typhimurinum and Ewcherichia coli. The enterochelin uptake system facilitates entry of iron complexed to enterochelin, a cyclic trimer of 2,3dihydroxybenzoylserine syntheized and excreted by the bacterium itself. This presumably represents the physiologically relevant system under most circunutances (3, 31). The fernchrome uptake system facilitates entry of iron complexed to siderophores produced by fimgi (3, 19, 23). A third high-affinity uptake systm facilitats entry ofiron-citrate complexes in E. coli but is not present in S. typhimurium (8, 32).