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K Horikoshi

Publications and source records attributed to K Horikoshi.

At least 19 recordsLinked to original sources
PubMed1995

Hydrostatic pressure promotes the acidification of vacuoles in Saccharomyces cerevisiae.

Application of hydrostatic pressure caused a delay or cessation of cell growth in Saccharomyces cerevisiae. The yeast vacuole is an acidic organelle involved in cellular ion homeostasis and degradation of proteins. Hydrostatic pressure promoted the acidification of the vacuoles in the strain IFO 2347. A pressure of 40 to 60 MPa reduced the vacuolar pH, defined using 6-carboxyfluorescein, from 6.05 to 5.88, while a pressure of 20 MPa did not affect the pH. Similar results were obtained with the strain X2180. Bafilomycin A1, a specific inhibitor of vacuolar H(+)-ATPase (V-H(+)-ATPase), caused a significant alkalization of vacuoles in the strain X2180. The pHs rose to 7.34 and 6.84 at both atmospheric pressure and a pressure of 40 MPa, respectively. Meanwhile, vacuolar accumulation of the weak base quinacrine was increased by a pressure of 40 MPa, suggesting that uptake of the dye was induced by the increased pH gradient across the vacuolar membrane.

Anti-Bacterial Agents↗
PubMed1995

Degradation of polyaromatic hydrocarbons by organic solvent-tolerant bacteria from deep sea.

We isolated three organic solvent (OS)-tolerant bacterial strains DS-1051, DS-1902, and DS-313 from a depth of 1,168 m in Sagami Bay, Japan. These isolates were tolerant to various kinds of toxic OSs such as benzene, toluene, and p-xylene. They also could degrade polyaromatic hydrocarbons, naphthalene or biphenyl, in a medium-OS (9:1) two-liquid-phase system. Percentage degradation of polyaromatic hydrocarbons in OS by these strains were higher than those obtained from cultures in which substrates were in the medium without OS.

Bacteria↗
PubMed1995

Effect of hydrostatic pressure on the synthesis of outer membrane proteins in Escherichia coli.

We examined the effects of hydrostatic pressure on the synthesis of Escherichia coli outer membrane proteins, particularly for the osmoregulated ImpC and OmpF porins. It was found that the expression of ompC and ompF was markedly reduced during the growth at high pressure, most likely at the transcriptional level. However, the signal transduction processes through the regulatory proteins, EnvZ and OmpR, was not influenced by the environmental pressure. It was also found that the expression of a presumed novel outer membrane protein, named OmpX, was affected by both the medium osmolarity and pressure in a manner independent of the function of EnvZ and OmpR.

Bacterial Outer Membrane Proteins↗
PubMed1995

Characterization of a mutation responsible for an alkali-sensitive mutant, 18224, of alkaliphilic Bacillus sp. strain C-125.

An alkali-sensitive mutant, 18224, of the alkaliphilic Bacillus sp. strain C-125 was characterized. The nucleotide sequence of the PvuI-NlaIV DNA fragment that recovers the alkaliphily of 18224 has been cloned from the mutant and sequenced. Comparison of the nucleotide sequences of the corresponding regions found a G to A substitution in the mutant. The mutation resulted in an amino acid substitution from 82Gly to Glu of the putative ORF3 product, which consisted a gene cluster of at least four tandemly located open reading frames. The ORF3 product was deduced to be an 112 amino acid polypeptide with hydrophobic properties, which was expressed using an in vitro translation system.

Alkalies↗
PubMed1995

Thermococcus peptonophilus sp. nov., a fast-growing, extremely thermophilic archaebacterium isolated from deep-sea hydrothermal vents.

Two extremely thermophilic archaebacteria, strains OG-1 and SM-2, were isolated from newly discovered deep-sea hydrothermal vent areas in the western Pacific ocean. These strains were cocci, obligately anaerobic Archaea about 0.7-2 microm in diameter. Optimum growth conditions for OG-1 and SM-2 were at 85-90 degrees C (range 60-100 degrees C), pH 6 (range pH 4-8), a NaCl concentration of 3% (range 1-5%), and a nutrient concentration (tryptone plus yeast extract) of 0.2% (range 0.005-5%). Elemental sulfur stimulated the growth rate fourfold. Ammonium slightly stimulated growth. Both tryptone and yeast extract allowed growth as sole carbon sources; these isolates were not able to utilize or grow exclusively on sucrose, glucose, maltose, succinate, pyruvate, propionate, acetate, or free amino acids. OG-1 showed the fastest growth rate within the genus Thermococcus. Growth was inhibited by rifampicin. The DNA G+C content was 52 mol%. Sequencing of their 16S rDNA gene fragment indicated that these isolates belonged to the genus Thermococcus. OG-1 and SM-2 were different than the described Thermococcus species. We propose that OG-1 belongs to a new species: Thermococcus peptonophilus.

Archaea↗
PubMed1994

High pressure conditions stimulate expression of chloramphenicol acetyltransferase regulated by the lac promoter in Escherichia coli.

Recombinant plasmids with the chloramphenicol acetyltransferase (CAT) structural gene behind several kinds of promoters were tested for expression in Escherichia coli during growth at atmospheric pressure (0.1 MPa) and at high pressure (30 MPa). Expression of the CAT gene from the lac promoter was remarkably activated (approx. 78-fold) by high pressure in the absence of the inducer isopropyl-beta-D-thiogalactopyranoside (IPTG). The stimulation of the CAT activity by the lac promoter at high pressure did not simply result from an increased plasmid copy number, because the CAT activities from the other promoters and beta-lactamase activities were unaffected at high pressure.

Atmospheric Pressure↗
PubMed1994

Characterization of a gene responsible for the Na+/H+ antiporter system of alkalophilic Bacillus species strain C-125.

An alkali-sensitive mutant, 38154, of the alkalophilic Bacillus sp. strain C-125 could not grow at an alkaline pH. The nucleotide sequence of a 3.7 kb parental DNA fragment that recovers the growth of 38154 at alkaline pH has four open reading frames (ORF1-4). By subcloning the fragment, we demonstrated that a 0.25 kb DNA region is responsible for the recovery. Direct sequencing of the mutant's corresponding region revealed a G to A substitution. The mutation resulted in an amino acid substitution from Gly-393 to Arg of the putative ORF1 product, which was deduced to be an 804-amino-acid polypeptide with a molecular weight of 89,070. The N-terminal part of the putative ORF1 product showed amino acid similarity to those of the chain-5 products of eukaryotic NADH quinone oxidoreductases. Membrane vesicles prepared from 38154 did not show membrane potential (delta psi)-driven Na+/H+ antiporter activity. Antiporter activity was resumed by introducing a parental DNA fragment which recovered the mutant's alkalophily. These results indicate that the mutation in 38154 affects, either directly or indirectly, the electrogenic Na+/H+ antiporter activity. This is the first report which shows that a gene responsible for the Na+/H+ antiporter system is important in the alkalophily of alkalophilic microorganisms.

Amino Acid Sequence↗
PubMed1994

Properties of two different Na+/H+ antiport systems in alkaliphilic Bacillus sp. strain C-125.

Na+/H+ antiport was studied in alkaliphilic Bacillus sp. strain C-125, its alkali-sensitive mutant 38154, and a transformant (pALK2) with recovered alkaliphily. The transformed was able to maintain an intracellular pH (pHin) that was lower than that of external milieu and contained an electrogenic Na+/H+ antiporter driven only by delta psi (membrane potential, interior negative). The activity of this delta psi-dependent Na+/H+ antiporter was highly dependent on pHin, increasing with increasing pHin, and was found only in cells grown at alkaline pH. On the other hand, the alkali-sensitive mutant, which had lost the ability to grow above pH 9.5, lacked the delta psi-dependent Na+/H+ antiporter and showed defective regulation of pHin at the alkaline pH range. However, this mutant, like the parent strain, still required sodium ions for growth and for an amino acid transport system. Moreover, another Na+/H+ antiporter, driven by the imposed delta pH (pHin > extracellular pHout), was active in this mutant strain, showing that the previously reported delta pH-dependent antiport activity is probably separate from delta psi-dependent antiporter activity. The delta pH-dependent Na+/H+ antiporter was found in cells grown at either pH 7 or pH 9. This latter antiporter was reconstituted into liposomes by using a dilution method. When a transmembrane pH gradient was applied, downhill sodium efflux was accelerated, showing that the antiporter can be reconstituted into liposomes and still retain its activity.

Alanine↗
PubMed1994

Mapping of organic solvent tolerance gene ostA in Escherichia coli K-12.

The extent of organic solvent tolerance was variable among strains of Escherichia coli K-12. Genetic analyses of n-hexane-tolerant strains indicated that a number of genes were involved in the solvent-tolerance phenotype. One such gene, designated ostA, was mapped at 1.2 min, close to pdxA. Transduction of ostA from a n-hexane-sensitive strain to a n-hexane-tolerant strain generated n-hexane-sensitive transductants. The sensitive transductant restored n-hexane-tolerance by transduction of ostA from a tolerant strain. Thus, the gene ostA is one of the genes that contributes to deciding the level of organic solvent tolerance in E. coli.

Conjugation, Genetic↗
PubMed1994

Preparation of organic solvent-tolerant mutants from Pseudomonas aeruginosa strain PAO1161.

Most organic solvents (OSs) are toxic and inhibit growth of microorganisms even at low concentrations. Therefore, they are used to sterilize microbial cultures and to maintain solutions in a sterile condition. However, the physiological basis of such phenomenon is poorly understood. Although there are some microorganisms that can utilize a number of OSs as their sole carbon and energy sources, OSs must be provided as a vapor or at a very low concentration to avoid growth inhibition.

Drug Tolerance↗
PubMed1994

Myogenesis in primary cell cultures from larvae of the abalone, Haliotis rufescens.

Myogenesis culminating in the differentiation of contracting myocytes occurs in primary cell cultures derived from premyogenic trochophore and early veliger larvae of Haliotis rufescens (red abalone, gastropod mollusc). No detectable muscle cells were present at the start of the primary cultures. Onset and organization of myofibrillogenesis in culture (revealed by histochemical and immunohistochemical detection of filamentous actin, myosin, and desmin) generally paralleled those of smooth muscle development in vivo, although development of cells with striated sarcomeres was occasionally observed in culture, but not in the intact larvae. Most of the muscle cells that developed in culture were mononucleate, although some multinucleate syncytia were observed. Dissociated larval cells remained viable up to 12 weeks, exhibiting an average of one to two divisions in the first six days, and attachment of approximately 6 to 8% of the original population. Cell culture and in vitro myogenesis of Haliotis myoblasts and myocytes will facilitate studies of the molecular mechanisms controlling early muscle development, and should provide a useful model system for biotechnological improvement of the abalone.

Actins↗
PubMed1993

A partial physical map for the chromosome of alkalophilic Bacillus sp. strain C-125.

Bacillus sp. strain C-125 has been chosen as a model alkalophilic bacterium to understand how adaptation to growth at high pH is achieved. To aid genetic analysis, we have started characterization of its genome. By using the two infrequently-cutting restriction endonucleases, AscI and Sse8387I, in conjunction with pulsed-field electrophoretic techniques, the size of the genome was found to be 3.7 Mb. Southern blot analysis of single, double and partial digests of Bacillus sp. strain C-125 DNA, using AscI-linking clones, gene probes and purified Bacillus sp. strain C-125 restriction fragments, allowed a putative chromosome map to be constructed.

Adaptation, Physiological↗
PubMed1993

Purification and some properties of an alkaline xylanase from alkaliphilic Bacillus sp. strain 41M-1.

An alkaliphilic Bacillus sp. strain, 41M-1, isolated from soil produced multiple xylanases extracellularly. One of these xylanases was purified to homogeneity by ammonium sulfate fractionation and anion-exchange chromatography. The moleculr mass of this enzyme (xylanase J) was 36 kDa, and the isoelectric point was pH 5.3. Xylanase J was most active at pH 9.0. The optimum temperature for the activity at pH 9.0 was around 50 degrees C. The enzyme was stable up to 55 degrees C at pH 9.0 for 30 min. Xylanase J was completely inhibited by the Hg2+ion and N-bromosuccinimide. The predominant products of xylan hydrolysate were xylobiose, xylotriose, and higher oligosaccharides, indicating that the enzyme was an endoxylanase. The apparent Km and Vmax values on xylan were 3.3 mg/ml and 1,100 micromol-1 mg-1, respectively. Xylanase J showed high sequence homology with the xylanases from Bacillus pumilus and Clostridium acetobutylicum in the N-terminal region. Xylanase J acted on neither crystalline cellulose nor carboxymethyl cellulose, indicating a possible application of the enzyme in biobleaching processes.

Amino Acid Sequence↗
PubMed1993

Structure of the 87-kDa beta-1,3-glucanase gene of Bacillus circulans IAM1165 and properties of the enzyme accumulated in the periplasm of Escherichia coli carrying the gene.

The nucleotides of a gene for the extracellular 87-kDa beta-1,3-glucanase of Bacillus circulans IAM1165 and its flanking regions were sequenced. The sequence showed an open reading frame for 877 amino acids, which corresponds to a precursor of the beta-1,3-glucanase. The coding region of 2631 bp is flanked by putative promoter and transcription terminator sequences. The signal peptide was considered to be consisted of 38 amino acids. The amino acid sequence of the mature enzyme composed of 839 amino acids showed high homology to that of the enzyme from B. circulans WL-12, although these enzymes are different in their sizes. A catalytic domain of the enzyme was estimated central region of the sequence on the basis of comparison of amono acid sequences of beta-1,3- or beta-1,3:1,4-glucanases. Properties of the periplasmic enzyme produced in Escherichia coli carrying the gene were identical with those of the extracellular enzyme produced by B. circulans IAM1165.

Amino Acid Sequence↗
PubMed1993

Expression of an 87-kD-beta-1,3-glucanase of Bacillus circulans IAM1165 in Saccharomyces cerevisiae by low-temperature incubation.

A DNA segment encoding a signal peptide from yeast invertase was fused in frame to bglH gene encoding 87-kD-beta-1,3-glucanase from Bacillus circulans IAM1165 and was expressed in the yeast Saccharomyces cerevisiae under the control of the GAL1 gene promoter. Yeast cells containing this fused gene produced active beta-1,3-glucanase in the medium after a long period of incubation at low temperature. The enzyme produced by yeast was heterogeneous in size, and larger than the enzyme produced by Escherichia coli.

Amino Acid Sequence↗