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At least 973 records · Page 54Linked to original sources
PubMed1968

Streptomycin resistance mutation in Escherichia coli: altered ribosomal protein.

Reconstitution of 30S ribosomal particles was performed with 16S ribosomal RNA, "core" proteins, and "split" proteins from 30S particles derived from streptomycin-sensitive and streptomycin-resistant Escherichia coli cells in various combinations. Analysis of streptomycin sensitivity of the reconstituted particles has shown that the alteration induced by the resistance mutation resides in the core proteins, and not in the RNA or in the split proteins of the 30S particles.

Bacterial Proteins↗
PubMed1970

Encapsidation of free host DNA by simian virus 40: a simian virus 40 pseudovirus.

Under specified growth conditions, simian virus 40 encapsidated host DNA in a noncircular form free of viral DNA. Two bands of virus particles were present in cesium chloride equilibrium density centrifugation. The host DNA species contained in the upper band was of a lower molecular weight than the DNA present in the mature virus in the lower band.

Animals↗
PubMed1967

Diploid hybridization in a heterothallic haploid yeast, Saccharomyces rouxii.

By crossing of a heterothallic haploid yeast, Saccharomyces rouxii, we have succeeded in obtaining diploid hybrids. This paper shows one possible method of breeding heterothallic haploid yeasts for industrial application. S. rouxii is highly salt-tolerant and plays an important role in shoyu and miso fermentation. Therefore, genetic improvements of the properties are of commercial importance. Since newly isolated S. rouxii could neither conjugate nor sporulate on sporulation media commonly used, a suitable medium for conjugation and sporulation of S. rouxii was firstly investigated. A 5% NaCl Shoyu-koji extract agar was found to be most efficient. Next, we tried to get diploid strains by mass culture of two mating types on the conjugation medium, but several phenomena made this difficult: (i) zygotes quickly sporulated before budding; (ii) several zygotes showed terminal budding, but the buds could not grow into diploid cells, suggesting they would be heterocaryon; and (iii) a few zygotes lost their viability. After trying to isolate and cultivate a large number of zygotes in various combinations of crossing by micromanipulation, we fortunately recognized that large cells arose from some combinations. The analysis of ploidy suggested that the large cells would be diploid. Also, they showed sporulation of typical Saccharomyces, i.e., two to four spores in an unconjugated ascus. The diploid strains thus obtained were highly salt-tolerant and stable in liquid medium. Therefore, the procedure presented here would be effective for breeding salt-tolerant S. rouxii.

Conjugation, Genetic↗
PubMed1969

Incidence of infectious drug resistance among lactose-fermenting bacteria isolated from raw and treated sewage.

Raw and treated sewage samples were examined for antibiotic-resistant, lactose-fermenting bacteria. Approximately 1% of the total lactose-fermenting bacteria were multiply resistant. Of these organisms, 50% were capable of transferring all or part of their resistance to a drug-sensitive recipient. Only 43% of those isolated on media containing a single antibiotic were capable of resistance transfer, whereas 57% of those recovered on multiple antibiotic plates transferred resistance. R factors conferring resistance to chloramphenicol, streptomycin, and tetracycline; streptomycin and tetracycline; and ampicillin, streptomycin, and tetracycline accounted for 22, 19, and 15%, respectively, of those identified. The data indicate a significant level of infectious drug resistance among the intestinal bacteria of the urban population.

Anti-Bacterial Agents↗
PubMed1970

Persistence of an Escherichia coli-Shigella flexneri hybrid in the intestinal tract of Macaca mulatta.

A live oral vaccine prepared from an Escherichia coli-Shigella flexneri 4b hybrid was administered by gavage to Macaca mulatta. In the three main studies involving 160 monkeys, three doses were used, generally consisting of 5 x 10(9) to 60 x 10(9) cells per dose, with an interval between doses of 6, 7, or 14 days. Rectal swab cultures at the time of the last vaccine dose, and 14 to 58 days later, revealed that the hybrid persisted in the intestinal tract for at least 7 days in 16%, and for at least 21 days in 8%, of the monkeys. Our findings are comparable to those of Formal et al. for shedding of an E. coli-S. flexneri 2a hybrid. Protection studies with the E. coli-S. flexneri 4b hybrid are indicated.

Administration, Oral↗
PubMed1969

Specific action of sodium dodecyl sulfate on the sex factor of Escherichia coli K-12 Hfr strains.

A specific action of sodium dodecyl sulfate (SDS) on the sex (F) factor in the integrated state of Escherichia coli K-12 Hfr H strain is reported. Growth of Hfr cells in Penassay Broth containing SDS results in the elimination of part or all of the F factor, yielding low and nonfertile variants of defective Hfr type and F(+) cells and also F(-) derivatives. Appearance of such variants was generally observed after the culture reached stationary phase. The frequencies of F(-) cells then increased. F(-) cells were usually isolated as the major population among survivors. Some defective variants of Hfr cells with an intermediate fertility between standard Hfr and F(+) cells had lost sensitivity toward the male-specific ribonucleic acid phage M12. Other defective Hfr variants with as much or less fertility than standard F(+) cells had also all lost sensitivity to phage M12. On single-colony isolation, they segregated nonfertile female H cells which, when infected with F, could restore high fertility with oriented transfer of the chromosome the same as that of the original Hfr H. Also, sensitivity to phage M12 was regained. Female H cells were characterized as those lacking fertility but still retaining a small segment of F or sfa locus at the original part of the chromosome, where newly infected F could attach. Similar results were obtained with two other Hfr strains. A possible mechanism of the specific action of SDS is discussed.

Coliphages↗