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Biomedical subjects

S Mitsuhashi

Publications and source records attributed to S Mitsuhashi.

At least 361 records · Page 20Linked to original sources
PubMed1973

Mutation of R factors capable of specifying hypersynthesis of penicillinase.

When strains harboring R factor and showing ampicillin (APC) resistance were inoculated on plates containing various concentrations of APC, mutants carrying various levels of APC resistance occurred at high frequencies. Increases in the level of APC resistance were due to a quantitative increase in the formation of penicillinase. By conjugation experiments and transduction analysis, the mutation was found to affect the gene (amp) governing APC resistance on the R factor. The R-factor mutants carrying high and stable APC resistance were conjugally transferred at the same frequency as their parent R factors, and the level of their resistance to drugs other than APC was not distinct from that conferred by their parents. Such R-factor mutants could easily be obtained from wild-type R factors carrying low APC resistance. The hypersynthesis of penicillinase by such R-factor mutants was considered to be due to the replication of the amp gene on the R factor at hyper-rates and the integration of multiple copies of the amp gene (amp-hyper) in the R-factor genome.

Ampicillin↗
PubMed1973

Sex pili mutants isolated by macarbomycin treatment.

Macarbomycin (MM) preferentially kills Escherichia coli carrying episomes derepressed for sex pili formation (drd episomes). Using MM, we have isolated various types of mutants from both F-lac.tet and R100-1 episomes and have classified them into two types by sex pili formation. Among 26 mutants, 20 could not produce pili and had lost both the ability for conjugal transmission and sensitivity to male phages. From 12 of these 20 mutants, revertants capable of pili formation could be obtained. Most of these had simultaneously regained susceptibility to MM, indicating that the MM susceptibility of E. coli carrying drd episomes is due to pili formation. Three of the revertants could not confer MM susceptibility on their host and two of them could not produce normal pili, indicating that there are some types of pili insensitive to MM. The six MM-resistant mutants could produce pili, but the frequency of pili formation was slightly lower than that of their parent episomes. Mutants of this type exhibited various degrees of decrease in conjugal transferability or male phage sensitivity, and one mutant produced pili that were altered in shape. It is suggested that this latter mutant became MM-resistant as a result of changes in the chemical composition of its pili.

Anti-Bacterial Agents↗
PubMed1973

Lividomycin resistance in staphylococci by enzymatic phosphorylation.

Enzymatic inactivation of lividomycin (LV) was attempted with nine clinical isolates of staphylococci including LV-susceptible and -resistant strains. LV inactivation and the incorporation into LV of (32)P from gamma-(32)P-adenosine triphosphate were demonstrated in the presence of cell-free extracts from LV-resistant strains but not from LV-susceptible ones. The enzyme was purified approximately 82-fold from a resistant Staphylococcus aureus strain by means of ammonium sulfate fractionation and column chromatography. Some properties of the partially purified LV-phosphorylating enzyme were quite similar to those of an enzyme from Escherichia coli carrying an R factor conferring LV resistance, and the phosphorylated product of the drug was also found to be identical with that produced by E. coli carrying an R factor, i.e., 5''-phosphoryl-LV.

Adenosine Triphosphate↗
PubMed1973

Mode of action of lividomycin on protein synthesis in Escherichia coli.

Lividomycin specifically inhibited bacterial protein synthesis and had codon misreading activity. Lividomycin, moreover, stimulated the binding of aminoacyl-transfer ribonucleic acid to ribosomes, but did not show any significant effects on the formation of aminoacyl-transfer ribonucleic acid and the puromycin reaction.

Amino Acids↗
PubMed1973

Penicillinases of Klebsiella pneumoniae and their phylogenetic relationship to penicillinases mediated by R factors.

On the assumption that the penicillinase determinants on a group of R factors conferring ampicillin resistance have a phylogenetically close relationship to the penicillinase gene of the Klebsiella group, the penicillinases from four strains of K. pneumoniae, GN69, GN1103R(-), GN422, and GN118, were purified 230- to 1,000-fold and compared with the known two R-factor-mediated penicillinases. By gel filtration on Sephadex G-75, the molecular weights were estimated to be 17,400, 18,100, 20,000 and 18,300, respectively, which are slightly lower than those of the R-factor penicillinases. The isoelectric points of the Klebsiella penicillinases were not in agreement with those of the R-factor penicillinases. All the enzymes showed a pH optimum between 6.3 to 7.2 and a temperature optimum of 45 C, and those properties, together with behavior towards inhibitors, were about the same as those in the R-factor penicillinases. The substrate specificity and the Michaelis constants of the Klebsiella penicillinases for penicillins and cephaloridine were broadly similar to those of the R-factor penicillinases, however, some variations were found even among the four penicillinases of K. pneumoniae. The reactivities of the four penicillinases of K. pneumoniae with the antiserum against one R-factor penicillinase were tested, and three of the four Klebsiella penicillinases were found to be indistinguishable immunologically from both R-factor penicillinases. The remaining Klebsiella penicillinase, from GN1103R(-), showed an immunological partial homology with the R-factor penicillinases.

Ampicillin↗