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Biomedical subjects

K Horikoshi

Publications and source records attributed to K Horikoshi.

At least 127 records · Page 7Linked to original sources
PubMed1995

A toluene-tolerant mutant of Pseudomonas aeruginosa lacking the outer membrane protein F.

The outer membrane protein profiles of a toluene-tolerant mutant, Pseudomonas aeruginosa, strain PAK103, were compared with those of its parent strain PAO1161. Protein F (OprF), the most abundant outer membrane protein in the parental strain PAO1161, was missing in the toluene-tolerant strain PAK103. The absence of OprF may lead to the loss of toluene diffusion across in the outer membrane of the mutant cells.

Amino Acid Sequence↗
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↗
PubMed1995

Structure-function relationship of the xylanase from alkaliphilic Bacillus sp. strain 41M-1.

Xylanase J from alkaliphilic Bacillus sp. strain 41M-1 contains a family G catalytic domain at the N-terminus, followed by a linker sequence and a functionally-unknown C-terminal domain. The mutational analysis of xylanase J indicated that Glu-93, Glu-183, Trp-18, Trp-86, Tyr-84 and Tyr-95 play an important role in the catalytic activity. A deletion derivative of xylanase J lacking the C-terminal domain retained its activity, suggesting that the C-terminal domain does not directly involved in catalysis.

Amino Acid Sequence↗
PubMed1995

Structure and heterologous expression of the gene encoding the cell surface glycoprotein from Haloarcula japonica strain TR-1.

The gene encoding the cell surface glycoprotein (CSG) of Haloarcula japonica strain TR-1 was cloned and sequenced. The structural gene consisted from an open reading frame of 2,586 bp. A potential promoter sequence was found about 150 bp upstream of the ATG initiation codon. N-terminal amino acid sequence of the Ha. japonica CSG revealed that the mature CSG consisted of 828 amino acids. Five potential N-glycosylation sites were found in the mature sequence. The cloned CSG gene of Ha. japonica was expressed in closely-related halophilic archaea.

Amino Acid Sequence↗
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

Characterization of a Protease from a Psychrotroph, Pseudomonas fluorescens 114.

A psychrotrophic bacterium isolated from river sediment was identified as Pseudomonas fluorescens 114. It grew at 0 degrees C and optimally at 20 degrees C. The bacterium produced a protease with a molecular weight of 47,000, which was stable in the pH range of 5 to 9 and worked optimally between pH 6.5 and 10. Activity was optimal at 35 degrees C and was lost immediately at 50 degrees C and after 5 min at 45 degrees C. At 0, 10, and 20 degrees C, 24, 38, and 57% of optimal activity were observed, respectively.

Journal Article↗
PubMed1994

Oxidative Bioconversion of Cholesterol by Pseudomonas sp. Strain ST-200 in a Water-Organic Solvent Two-Phase System.

Pseudomonas sp. strain ST-200, which is capable of conversion of cholesterol, was isolated from humus soil. This organism effectively modified cholesterol dissolved in an organic solvent by dehydrogenation and oxygenation. When the organism was grown in a medium overlaid with a 10% volume of a mixed organic solvent (p-xylene and diphenylmethane; 3:7, vol/vol) containing cholesterol (20 mg/ml), the cholesterol concentration in the organic solvent was reduced to only 0.4 mg/ml after 8 days. Although the organism did not assimilate cholesterol, 98% of the cholesterol initially present disappeared. The organic solvent layer contained two major and three minor compounds converted from cholesterol. The major compounds were 6beta-hydroxycholest-4-en-3-one (8.9 mg/ml) and cholest-4-ene-3,6-dione (7.6 mg/ml). The concentrations of these compounds were equivalent to 43 and 37% of the cholesterol initially present. This organism would provide an effective and convenient system to oxidize the C-3 and -6 positions of cholesterol by introduction of a hydroxyl or ketone group.

Journal Article↗
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

Identification of 2-amino-2,6-dideoxy-D-glucose (D-quinovosamine), isolated from the cell walls of the alkaliphilic Bacillus sp. Y-25, by 500-MHz 1H NMR spectroscopy.

Cell walls of alkaliphilic Bacillus strain Y-25 are composed of gamma-peptidoglycan and two acidic polymers. An amino sugar, which was a min component of one acidic polymer, did not correspond to any of the commercially available hexosamines. The amino sugar was isolated from the hydrolysate of the acidic polymer, purified, and identified as D-quinovosamine (2-amino-2,6- dideoxy-D-glucose) by 500-MHz NMR spectroscopic analysis and polarimetry.

Bacillus↗
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↗