Biomedical subjects

H Ishiwa

Publications and source records attributed to H Ishiwa.

13 recordsLinked to original sources

PubMed1991

Shuttle plasmid vectors for Lactobacillus casei and Escherichia coli with a minus origin.

Recombinant plasmids which can be used as shuttle vectors between Escherichia coli and the industrially used strains of Lactobacillus casei were constructed. They have replication regions closely related to those of pUB110 and are likely to replicate by a rolling-circle mechanism via a plus-strand-specific DNA intermediate in L. casei. Both orientations of palA from the staphylococcal plasmid pC194 and those of the intergenic region from coliphage M13 are identified as active minus origins in L. casei, in contrast to the pAM alpha 1 delta 1-derived BA3 minus origin which does not function in L. casei. Stability of the plasmids increased in L. casei when one of these two active minus origins was inserted. All the DNA sequences of the constructed vectors were known.

Base Sequence↗

PubMed1990

Incomplete maternal transmission of mitochondrial DNA in Drosophila.

The possibility of incomplete maternal transmission of mitochondrial DNA (mtDNA) in Drosophila, previously suggested by the presence of heteroplasmy, was examined by intra- and interspecific backcrosses of Drosophila simulans and its closest relative, Drosophila mauritiana. mtDNAs of offspring in these crosses were characterized by Southern hybridization with two alpha-32P-labeled probes that are specific to paternal mtDNAs. This method could detect as little as 0.03% paternal mtDNA, if present, in a sample. Among 331 lines that had been backcrossed for ten generations, four lines from the interspecific cross D. simulans (female) x D. mauritiana (male) showed clear evidence for paternal leakage of mtDNA. In three of these the maternal type was completely replaced while the fourth was heteroplasmic. Since in this experiment the total number of fertilization is known to be 331 x 10 = 3310, the proportion of paternal mtDNA per fertilization was estimated as about 0.1%. The mechanisms and evolutionary significance for paternal leakage are discussed in light of this finding.

Animals↗

PubMed1987

Analysis of nucleotide substitutions of mitochondrial DNAs in Drosophila melanogaster and its sibling species.

To study the rate and pattern of nucleotide substitution in mitochondrial DNA (mtDNA), we cloned and sequenced a 975-bp segment of mtDNA from Drosophila melanogaster, D. simulans, and D. mauritiana containing the genes for three transfer RNAs and parts of two protein-coding genes, ND2 and COI. Statistical analysis of synonymous substitutions revealed a predominance of transitions over transversions among the three species, a finding differing from previous results obtained from a comparison of D. melanogaster and D. yakuba. The number of transitions observed was nearly the same for each species comparison, including D. yakuba, despite the differences in divergence times. However, transversions seemed to increase steadily with increasing divergence time. By contrast, nonsynonymous substitutions in the ND2 gene showed a predominance of transversions over transitions. Most transversions were between A and T and seemed to be due to some kind of mutational bias to which the A + T-rich mtDNA of Drosophila species may be subject. The overall rate of nucleotide substitution in Drosophila mtDNA appears to be slightly faster (approximately 1.4 times) than that of the Adh gene. This contrasts with the result obtained for mammals, in which the mtDNA evolves approximately 10 times faster than single-copy nuclear DNA. We have also shown that the start codon of the COI gene is GTGA in D. simulans and GTAA in D. mauritiana. These codons are different from that of D. melanogaster (ATAA).

Amino Acid Sequence↗

PubMed1986

Protoplast fusion of Lactobacillus fermentum.

Tetracycline-resistant (Tetr) erythromycin-resistant (Eryr) fusants of Lactobacillus fermentum 604 carrying a 10-megadalton Tetr plasmid and L. fermentum 605 carrying a 38-megadalton Eryr plasmid were obtained by means of polyethylene glycol-induced protoplast fusion.

Drug Resistance, Microbial↗

PubMed1984

New shuttle vectors for Escherichia coli and Bacillus subtilis. I. Construction and characterization of plasmid pHY460 with twelve unique cloning sites.

We have constructed chimeric plasmid vectors, pHY460 and pHY310, from the streptococcal tetracycline resistance (TcR) plasmid pAM alpha 1 (9.2 kb) and the Escherichia coli vector pACYC177 (3.7 kb). These bifunctional plasmids can replicate and express the TcR gene in both E. coli and Bacillus subtilis. Plasmids pHY460 (7.0 kb) and pHY310 (4.8 kb) contain the TcR gene of pAM alpha 1 and the ampicillin resistance (ApR) gene of pACYC177. Both plasmids showed high transformation efficiency in both host cells. pHY460 was maintained stably in B. subtilis and, thus, is a useful shuttle vector functioning in E. coli and B. subtilis. The PvuI, PstI, BglI and BanI sites in the ApR gene and the HpaI, BalI and EcoRV sites in the TcR gene can be used for selection of recombinant plasmids by insertional inactivation. In addition, plasmid pHY460 has unique sites for SacII, BstEII, XbaI, AvaI and BamHI.

Bacillus subtilis↗

PubMed1974