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PubMed1975

Chromosome transfer in Proteus mirabilis mediated by hybrid plasmid.

A previously-described fused plasmid, P-lacRIdrd19, was found to mediate chromosomal transfer between cells of Proteus mirabilis strain PM5006; PM5006-(P-lacRIdrd19) was usually the donor and various auxotrophs of PM5006 resistant to nalidixic acid and/or streptomycin were recipients. The donor was usually counterselected with nalidixic acid and/or high concentrations of streptomycin. Recombination experiments with single markers indicated a 40-fold variation in recombination frequencies for different markers. Mapping double-auxotrophic markers by their gradient of transmission confirmed this variation and placed each of two independent isolates of eight markers in a linkage group his-ser-ura-pyrB-trp-cys-ade-ilv. Some donor markers did not register. Despite low recombination frequencies, interrupted mating experiments showed a polarity of early marker transfer. The segregation of unselected markers confirmed the order of some markers and showed that genetic material passed from the presumptive donor to the recipient. Recipients with two auxotrophic markers which could not be cotransduced by phage 5006M were converted to prototrophy by conjugation. The plasmid transferred to recipients at high frequency and all recombinants carried it. Recombinants could act as donors in further matings. Recombinants were fully susceptible to phage 5006M, unlike transductants of PM5006 by this phage. Direct involvement of the plasmid was indicated by drastically diminished recombination frequencies in crosses with recipients carrying P-lac as resident. P-lac had previously been shown to reduce the frequency of transfer of the hybrid plasmid to cells harbouring it. The histidine region was the first to register in recipients and recombined at the highest frequency of 5 times 10-6/donor cell. Some temporary association of plasmid and perhaps only the histidine region of the chromosome is favoured as the mechanism of chromosomal transfer. This could explain why not all donor markers could be mapped. Transduction and transformation were excluded as the cause of results.

Chromosome Mapping↗
PubMed1975

R factors from Serratia marcescens.

In recent years, Serratia marcescens has become established in certain localities as an agent of hospital infection and cross-infection (Clayton & von Graevenitz, 1966; Wilfert, Barrett & Kass, 1968; Davis, Foltz & Blakemore, 1970; Wilkowske, Washington, Martin & Ritts, 1970). In general, strains of S. marcescens isolated from infective lesions differ from those from other sources in being non-pigmented and antibiotic resistant (Ewing, Johnson & David, 1962; Clayton & von Graevenitz, 1966). Medeiros & O'Brien (1969) and Schaefler et al. (1971) described strains of S. marcescens, isolated from hospital patients, which were able to transfer R factors to Escherichia coli. Transfer of resistance to E. coli has also been reported from strains of S. marcescens isolated in France (Grimont & Dulong de Rosnay, 1972; Scavizzi, 1972; Lemosquet-Villemon, Morel & Freymuth, 1973)9 We have collected strains of S. marcescens, most, but not all, clinical isolates, from widely separate geographical areas; each strain was tested for antibiotic resistance and for R factors transmissible to E. coli K129 The R factors were classified by compatibility in K12 (Datta, 1974). Our purpose was to find out how much of the antibiotic resistance observed in S. marcescens is characteristic of that genus and to what extent it is shared with other bacterial genera (Coetzee, Datta & Hedges, 1972; Datta & Hedges, 1972a; Hedges, 1974). The R factors described by Medeiros & O'Brien (1969) and Lemosquet-Villemon et al. (1973) were included in this study.

Anti-Bacterial Agents↗
PubMed1975

Transmissible substrate-utilizing ability in enterobacteria.

Three of 152 strains of Escherichia coli transmitted their ability to utilize sucrose (Sac+) to other strains by conjugation. The transfer factor of one of them and of a Sac+ Salmonella thompson strain was thermosensitive. The raffinose-utilizing ability of 27 of 163 E. coli strains was also transmissible. Transmissible raffinose-utilizing ability was a feature of porcine enterpathogenic strains possessing the K88 antigen. The determinants controlling raffinose utilization (Raf) and K88 antigen production were commonly transmitted together from these strains; so also was the determinant controlling enterotoxin production, but to a lesser extent. It was not possible to transfer lactose-utilizing ability from 320 strains of E. coli, salicin-utilizing ability from 12 strains of E. coli or dulcitol-utilizing ability from 99 strains of E. coli and 88 strains of salmonellae. Sucrose- and raffinose-utilizing ability were transmitted separately to several Salmonella sp., including Salm. typhi, to Shigella flexneri and Sh. sonnei and to a variety of strains of E. coli. A strain of Salm. typhimurium in which Sac had been established and a strain of E. coli in which Raf had been established survived less well in the alimentary tract of chickens than their Sac minus or Raf minus parent strains.

Animals↗
PubMed1975

Transfer of drug resistance to myxococcus from bacteria carrying drug-resistance factors.

Resistance to chloramphenicol was successfully transferred from strains of Escherichia coli carrying R factors representative of compatibility groups F, W, S and N to strains of Myxococcus xanthus and M. fulvus. Resistance to kanamycin was transferred from an R factor in group S, and to neomycin from an R factor of group P. Myxobacterial strains differed in their capacity to take up the resistances and also in the stability of the resistance character. strains of M. fulvus were obtained that acquired resistance to chloramphenicol without exposure to R plus eubacterial strains. Cell-free preparations of all the chloramphenicol-resistant strains catalysed the acetylation of the drug. Cholramphenicol resistance was successfully transferred from the presumed R plus strains of Myxococcus and also from the spontaneously occurring chloramphenicol-resistant M. fulvus to other Myxococcus strains. Moreover, recombinants resistant to both rifampicin and 5-fluorouracil were obtained, though infrequently, by mixing Myococcus strains resistant to rifampicin and chloramphenicol with other myxococci resistant to 5-fluorouracil, both when the chloramphenicol resistance was derived from S-a (group W) and when it was the endogenous M fulvus resistance. Thus it appears that S-a and a new chloramphenicol resistance factor from M. fulvus will mobilize a chromosomal genetic marker in Myxococcus.

Acetylation↗
PubMed1975

Restriction of DNA in Yersinia enterocolitica detected by recipient ability for a derepressed R factor from Escherichia coli.

A derepressed R factor, RY2drd2, was transferred at a frequency of 5x10minus 3 between two strains of Yersinia enterocolitica mated on a membrane. Under the same conditions transfer of this R factor from Escherichia coli to Y. enterocolitica was observed at a frequency of only 7-7x10minus 6. This frequency was greatly increased when the recipient strain was heat-treated before mating. Heat exposure for optimum fertility was 50 to 52 degrees C for a period of 2 to 3 min. Mutants of Y. enterocolitica were isolated which were infected by RY2drd2 from E. coli or from Y. enterocolitica at the same frequency. These observations strongly suggest that a DNA restriction and modification system in Y. enterocolitica causes its low recipient ability for plasmids from other species.

Conjugation, Genetic↗
PubMed1975

The genetics of tetracycline resistance in Staphylococcus aureus.

Eighty-one strains ofStaphylococcus aureus that appeared to be tetracycline resistant on the basis of a preliminary disc-diffusion test were examined fro resistance to tetracycline and to the semi-synthetic tetracycline, minocycline. Minimum inhibitory concentration (m.i.c.) values for both drugs were determined after induction of the strains by growth for 2 h in sub-inhibitory concentrations fo tetracycline. Forty-seven strain (58 percent) had m.i.c. values for minocycline of I2.5 MUg/ml or greater, and were considered to be minocycline resistant. An additional ten strains had m.i.c.r greater, and were considered to be minocycline resistant. An additional ten strains had m.i.c.values for minocycline of 3.I25 to 6-25 MUg/ml and were classified as low-level resistant strain. It appears, therefore, that a faily high proportion fo tetracycline-resistant strains isolated at the present time are resistant of concentrations of minocycline unattainbale in vivo with the recommended dosage forthis antibiotic (Fishk & Tunevall, 1969). Transductioal analysis of the genetic determinantswo types of resistance to high concentrations of tetracycline. Strains in the first categroy (A)were inducibly resistant to tetracycline but sensitive to minocycline; in these strains the resistance determinant was plasmid-borne. Strains in the second categroy (B) were resistant to both tetracycline and minocycline and had low induction ratios for tetracycline resistance; the genetic determinant for resistance in these strains was chromosomal. In addition, certain strains incategroy A were found to carry a chromosomal gene controlling low-level resistance to tetracycline and minocycline. This low-level resistance to tetracycline was masked in the presence of the tetracycline plasmide but could be demonstrated after loss of the plasmid. The results suggest that more than one mechanism of resistance to tetracyclines may exist in staphylococci.

Drug Resistance, Microbial↗
PubMed1975

Transfer of antibiotic resistance plasmid RP1 into Pseudomonas glycinea and Pseudomonas phaseolicola in vitro and in planta.

The wide host-range antibiotic resistance plasmid RP1 was transferred from Pseudomonas aeruginosa via Escherichia coli into Pseudomonas glycinea. The plasmid was then acquired by Pseudomonas phaseolicla both in vitro and in planta in Phaseolus limensis leaves and pods. This was the first step in the design of a model system to determine the possible epidemiological significance of antibiotic resistance plasmids in the control of plant disease.

Acridines↗
PubMed1975

Manganese mutagenesis in yeast. A practical application of manganese for the induction of mitochondrial antibiotic-resistant mutations.

When yeast cells were incubated for 4 to 8 h in yeast extract-peptone-glucose medium, pH 6, containing 8 mM-manganese, and then plated on selective media, there was a strong induction of antibiotic-resistant mutations. Indirect evidence suggests that practically all resistant mutants selected were of independent origin. The analysis of manganese-induced resistant mutants showed that most were extranuclear, while those tested showed recombination with known mitochondrial markers. Our results suggest that manganese can be considered as a mutagen which specifically induces mitochondrial mutations in Saccharomyces cerevisiae.

Anti-Bacterial Agents↗