Kazuhito Itoh

Shimane University, Matsu, Shimane, Japan

Are you Kazuhito Itoh?

Claim your profile

Publications (33)57.37 Total impact

  • Shohei Hayashi · Kazuhito Itoh · Kousuke Suyama
    [Show abstract] [Hide abstract]
    ABSTRACT: Synechococcus leopoliensis CCAP1405/1 cannot grow on common solid media; however, the strain can grow when co-cultured with Bacillus subtilis 168. Gene-disruptant strains of B. subtilis 168 by pMUTINs at the following sites lost the ability to support the growth of S. leopoliensis CCAP1405/1 on agar media: yxeO and yufO (transporter), yxdK (histidine kinase), sdhC (succinate dehydrogenase), yvgQR (sulfite reductase), acoB (acetoin dehydrogenase), yusE (thioredoxin), yrdA (function unknown). Involvement of the assimilatory sulfate reduction pathway was the suggested reason for loss of the function.
    No preview · Article · Apr 2015 · Microbial Ecology
  • Yuta Suzuki · Dinesh Adhikari · Kazuhito Itoh · Kousuke Suyama
    [Show abstract] [Hide abstract]
    ABSTRACT: Background and aims Bradyrhizobium japonicum and Bradyrhizobium elkanii dominated soybean nodules in temperate and subtropical regions in Nepal, respectively, in our previous study. The aims of this study were to reveal the effects of temperature on the nodulation dominancy of B. japonicum and B. elkanii and to clarify the relationship between the effects of temperature and the climate-dependent distribution of Bradyrhizobium species. Methods A laboratory competition experiment was conducted between B. japonicum and B. elkanii strains isolated from the same temperate location in Nepal. A mixture of each strain was inoculated into sterilized vermiculite with or without soybean seeds, and inoculated samples were incubated at 33/27 (day/night) and 23/17 °C. Relative populations in the non-rhizosphere, rhizosphere, and nodules were determined by competitive PCR using specific primers for each strain at 0, 1, 2, and 4 weeks after inoculation. Results Both separately inoculated B. japonicum and B. elkanii strains formed nodules at both temperatures. Under competitive conditions, B. japonicum strains dominated at low temperature; however, at high temperature, both strains achieved co-nodulation in 1 week, with B. elkanii dominating after 2 weeks. The relative populations of both strains were similar in the non-rhizosphere and rhizosphere at low temperature, but B. elkanii strains dominated in these regions at high temperature. Conclusions The domination of B. japonicum strains in nodules at the low temperature appeared to be due to preferential infection, while the domination of B. elkanii strains at high temperature appeared to be due to the higher population of B. elkanii in the non-rhizosphere and rhizosphere, in addition to its domination in nodules after co-nodulation. The effects of temperature on the competition between B. japonicum and B. elkanii strains were remarkable and corresponded with the distribution of bradyrhizobial species in Nepal.
    No preview · Article · Jan 2014 · Plant and Soil
  • Source
    Kazuhito Itoh
    [Show abstract] [Hide abstract]
    ABSTRACT: Ecological properties of microorganisms involved in aerobic degradation of 2,4-D, 2,4,5-T and salithion and in anaerobic degradation of chlorophenols were examined based on their phylogenetic classification, identification and characterization of genes and enzymes, and/or distribution, diversity and succession in the soil or sediment environment by culture- and molecular-based methods. Side effects of pesticides were evaluated on the soil microbial community by analyzing community-level physiological profiles, on duckweed proliferation considering long-term exposure, recovery potential from the damage and mixture effects of the pesticides, and on river biofilm by assembling a model river biofilm. (C) Pesticide Science Society of Japan
    Preview · Article · Jan 2014 · Journal of Pesticide Science
  • Source
    Dinesh Adhikari · Kazuhito Itoh · Kousuke Suyama
    [Show abstract] [Hide abstract]
    ABSTRACT: Background and Aims This study was conducted to reveal the genetic diversity of common bean (Phaseolus vulgaris L.) nodulating rhizobia in various agroecological regions in Nepal. Method A total of 63 strains were isolated from common bean grown in the soils collected from seven bean fields in Nepal and characterized based on the partial sequences of 16S–23S internal transcribed spacer (ITS) regions, 16S rDNA, nodC, and nifH. Symbiotic properties of some representative strains with host plants were examined to elucidate their characteristics in relation to genotype and their origin. Results The isolated strains belonged to Rhizobium leguminosarum, Rhizobium etli, Rhizobium phaseoli, and one unknown Rhizobium lineage, all belonging to a common symbiovar (sv.) phaseoli. Nine ITS genotypes were detected mainly corresponding to a single site, including a dominant group at three sites harboring highly diverse multiple ITS sequences. Three symbiotic genotypes corresponded to a geographical region, not to the ribosomal DNA group, suggesting horizontal transfer of symbiotic genes separately in each region. Great differences in nitrogenase activity and nodule forming ability among the strains irrespective of their species and origin were observed. Conclusions Nepalese Himalaya harbor phylogenetically highly diverse and site-specific strains of common bean rhizobia, some of which could have high potential of symbiotic nitrogen fixation.
    Preview · Article · Jul 2013 · Plant and Soil
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Butyric acid, a short-chain fatty acid and one of the main metabolites of intestinal microbial fermentation of dietary fiber, has been shown to have an important role in maintaining the integrity of the intestinal mucosa, while it also has been shown to exert potent anti-inflammatory effects both in vitro and in vivo. However, the precise mechanisms underlying those effects have not been fully identified. We exposed colonic epithelial cells to butyric acid, then extracted total RNA samples, and subsequently hybridized them to microarray chips. Among the upregulated genes, milk fat globule-epidermal growth factor 8 (MFG-E8) was elevated by approximately fivefold. We previously reported that the potential therapeutic benefits of MFG-E8 in intestinal tissue injury were dependent not only on enhanced clearance of apoptotic cells but also required diverse cellular events for maintaining epithelial integrity. The influence of butyric acid on cell function is often attributed to its inhibition of histone deacetylases (HDACs). We found that acetylation on histone 3 lysine 9 (acetyl-H3K9) around the MFG-E8 promoter was significantly increased with butyric acid exposure. Experimental colitis was induced by administration of dextran sodium sulfate (DSS) in C57BL/6N (MFG-E8(+/+)) and MFG-E8(-/-) mice. Although the colonic bacterial compositions in wild-type (WT) and MFG-E8(-/-) mice were not significantly different, intrarectal administration of butyric acid during an acute phase of colitis attenuated intestinal inflammatory parameters and inhibited body weight loss in the WT mice. Our novel findings suggest that butyric acid has significant anti-inflammatory effects partly via MFG-E8 on DSS-induced murine experimental colitis.Laboratory Investigation advance online publication, 10 June 2013; doi:10.1038/labinvest.2013.70; published online 10 June 2013.
    Full-text · Article · Jun 2013 · Laboratory Investigation
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Sixty-nine fungal strains were isolated country-wide from ten Vietnamese soils, in areas both with and without a history of exposure to Agent Orange, and their degrading activities on the phenoxy acid herbicides 2,4-D and 2,4,5-T, as well as related compounds, were examined. Among taxonomically various fungi, 45, 12 and 4% of the isolates degraded phenoxyacetic acid (PA), 2,4-D and 2,4,5-T, respectively. While the PA-degrading fungi were distributed to all sites and among many genera, the 2,4-D-degraders were found only in order Eurotiales in class Eurotiomycetes. All of the 2,4,5-T-degrading fungal strains were phylogenetically close to Eupenicillium spp. and were isolated from southern Vietnam. As a degradation intermediate, the corresponding phenol compounds were detected in some strains. The degradation substrate spectrum for 26 compounds of Eupenicillium spp. strains including 2,4,5-T-degraders and -non-degraders seemed to be related to phylogenetic similarity and soil sampling location of the isolates. These results suggest that the heavily contaminated environments enhanced the adaptation of the phylogenetic group of Eupenicillium spp. toward obtaining the ability to degrade 2,4,5-T. © 2012 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. Allrights reserved.
    Preview · Article · Nov 2012 · FEMS Microbiology Ecology
  • [Show abstract] [Hide abstract]
    ABSTRACT: Backgroud and aims This study was conducted to reveal the genetic diversity of soybean-nodulating rhizobia in Nepal in relation to climate and soil properties. Method A total of 102 bradyrhizobial strains were isolated from the root nodules of soybeans cultivated in 12 locations in Nepal varying in climate and soil properties, and their genetic diversity was examined based on 16S rDNA, ITS regions of 16S–23S rDNA, nodC and nifH. In vitro growth properties of some representative strains were examined to elucidate their characteristic distribution in Nepal. Results Four species of the genus Bradyrhizobium were isolated, and B. japonicum dominated at temperate locations, while in subtropical locations, B. elkanii, B. yuanmingense, and B. liaoningense dominated at acidic, moderately acidic, and slightly alkaline soils, respectively. The relative nodule occupancies could not be fully explained by their in vitro growth properties. Similar nodC and nifH genes among the strains suggested co-evolution of these genes also in Nepal, probably through horizontal gene transfer. Conclusions The influence of climate and soil pH on diversity at the sub-species level was revealed. It is concluded that the highly diverse climate and soils in Nepal might be conducive for the existence of diverse soybean rhizobial strains.
    No preview · Article · Aug 2012 · Plant and Soil
  • Shohei Hayashi · Kazuhito Itoh · Kousuke Suyama
    [Show abstract] [Hide abstract]
    ABSTRACT: The cyanobacterium Synechococcus leopoliensis CCAP1405/1 does not grow on common solid media made of agar, agarose HT, noble agar, gelrite and gelatin, although it grows in liquid media with the same components. The inoculation of S. leopoliensis CCAP1405/1 at a high initial cell density allowed it to grow on the agar media, and co-inoculation with one of the heterotrophic bacterial strains belonging to a wide range of phylogeny, showed the same effects even at a low initial cell density of S. leopoliensis CCAP1405/1. The addition of thiosulfate and high concentrations of vitamin B(12), biotin and thiamine also supported growth on solid media, but catalase had no effect. On inorganic solid media, the autotrophic cyanobacterial strain supported the growth of heterotrophic bacteria, suggesting mutual interaction.
    No preview · Article · Jun 2011 · Microbes and Environments
  • Source
    Munir Mohammad · Kazuhito Itoh

    Preview · Chapter · Jan 2011
  • [Show abstract] [Hide abstract]
    ABSTRACT: Due to the high importance of biofilms on river ecosystems, assessment of pesticides' adverse effects is necessary but is impaired by high variability and poor reproducibility of both natural biofilms and those developed in the laboratory. We constructed a model biofilm to evaluate the effects of pesticides, consisting in cultured microbial strains, Pedobacter sp. 7-11, Aquaspirillum sp. T-5, Stenotrophomonas sp. 3-7, Achnanthes minutissima N71, Nitzschia palea N489, and/or Cyclotella meneghiniana N803. Microbial cell numbers, esterase activity, chlorophyll-a content, and the community structure of the model biofilm were examined and found to be useful as biological factors for evaluating the pesticide effects. The model biofilm was formed through the cooperative interaction of bacteria and diatoms, and a preliminary experiment using the herbicide atrazine, which inhibits diatom growth, indicated that the adverse effect on diatoms inhibited indirectly the bacterial growth and activity and, thus, the formation of the model biofilm. Toxicological tests using model biofilms could be useful for evaluating the pesticide effects and complementary to studies on actual river biofilms.
    No preview · Article · Jan 2011 · Archives of Environmental Contamination and Toxicology
  • Shohei Hayashi · Kazuhito Itoh · Kousuke Suyama
    [Show abstract] [Hide abstract]
    ABSTRACT: The dose response of the biological parameters of the model river biofilm, consisting of two diatom strains and three bacterial strains on the glass surface, was examined with atrazine. Good correlations (r(2)=0.90-0.93) between the atrazine log concentration and the relative increase rates of microbial cell numbers and the amount of chlorophyll a in the model biofilm formation were shown, and similar EC(50) values for the biological parameters including esterase activity were tentatively obtained as an endpoint. The results suggested that this model biofilm could be used for testing the potential effects of pesticides on natural river biofilms at a community level with high reproducibility. (C) Pesticide Science Society of Japan
    No preview · Article · Jan 2011 · Journal of Pesticide Science
  • [Show abstract] [Hide abstract]
    ABSTRACT: Dechlorination of all mono- and dichlorophenol isomers in anaerobic sediment samples of estuarine Lake Shinji and Lake Nakaumi was examined to characterize the chlorophenol-dechlorinating microbial communities in the environments with different salinity levels. Dechlorination was observed only in 2-chlorophenol (2-CP), 3-chlorophenol (3-CP) and 2,6-dichlorophenol (2,6-DCP), and in 2-CP and 2,6-DCP in the Lake Shinji and Nakaumi sediment, respectively. In the sediment of Lake Shinji, the highest activity was observed without adding sodium chloride and sulfate, whereas in the Lake Nakaumi sediment, the highest activity was at 0.7 % of sodium chloride and 6.0 mM of sodium sulfate. The chlorophenols were degraded to benzoate via phenol in both sediments under methanogenic conditions. Benzoate then disappeared from the cultures. All microbial consortia enriched with each monochlorophenol dechlorinated 2-CP, but showed different substrate specificities for dichlorophenols as follows: 2-CP-enriched consortium dechlorinated 2,3-dichlorophenol and 2,6-DCP, 3-CP-enriched consortium dechlorinated all dichlorophenol isomers, and 4-chlorophenol-enriched consortium dechlorinated 2,4-dichlorophenol and 2,6-DCP. Maintenance of the population by halorespiration was suggested in the dechlorination of 2-CP.
    No preview · Article · Jul 2010 · Journal of Environmental Science and Health Part B Pesticides Food Contaminants and Agricultural Wastes
  • Nguyen L Huong · Kazuhito Itoh · Kousuke Suyama
    [Show abstract] [Hide abstract]
    ABSTRACT: Changes in the bacterial community in soil-water suspensions during the enrichment period of 2,4-D and 2,4,5-T degraders were examined using denaturing gradient gel electrophoresis (DGGE) analysis of the 16S rRNA gene. The nucleotide sequences of almost all major bands at the degradation of 2,4-D and 2,4,5-T corresponded to those of 2,4-D- and 2,4,5-T-degrading isolates, and successions of diverse 2,4-D- and 2,4,5-T-degrading bacterial communities were demonstrated in the DGGE profile. These results suggested that 2,4-D- and 2,4,5-T-degrading isolates were responsible for the degradation of 2,4-D and 2,4,5-T in soil-water suspensions; however, one major band of a non-degrader was found in some cases. Therefore, to elucidate the relationship between the structures and functions of bacterial communities, the importance of a combined approach using both culture-dependent and -independent methods was demonstrated.
    No preview · Article · Jan 2008 · Microbes and Environments
  • Sonny Conde · Kousuke Suyama · Kazuhito Itoh · Hiroki Yamamoto
    [Show abstract] [Hide abstract]
    ABSTRACT: A commercially available fenitrothion-ELISA kit, designed for residue analysis of crop samples, was applied in a method development study using 10 different soils spiked with the target pesticide. Recoveries determined by gas chromatography (GC) were compared to those in ELISA analysis. Recoveries in ELISA were biased high in six soil samples which had low pH and high sand content. The range of recoveries in 10 soils was from 87 to 163% while, in contrast, GC recovery was 72-86%. Soil matrix, such as high-molecular-weight organics and divalent cations, influenced the ELISA reaction to cause an overestimation of recovery.
    No preview · Article · Jan 2008 · Journal of Pesticide Science
  • Munir Mohammad · Kazuhito Itoh · Kousuke Suyama
    [Show abstract] [Hide abstract]
    ABSTRACT: The effects of 9 herbicides in 5 different families on the growth of Lemna sp. were studied through 7-day exposure. The treated plant was transferred to fresh medium to observe recovery from inhibition. Inhibition and the recovery of growth were estimated on the basis of frond number and area, and expressed as the relative growth rate (RGR) compared with the untreated control. Patterns of RGR in exposure and recovery periods showed a tendency corresponding to the different families of herbicides. Considering the recovery potential of Lemna sp. from inhibition by chemicals and the large difference in RGRs between exposure and recovery periods, it is appropriate to take them into account for ecotoxicological risk assessment of chemicals.
    No preview · Article · Jan 2008 · Journal of Pesticide Science
  • Sonny Conde · Kousuke Suyama · Kazuhito Itoh
    [Show abstract] [Hide abstract]
    ABSTRACT: Improvement of the commercially available fenitrothion-ELISA kit for soil residue analysis was examined. Recovery trials were conducted with 5 soils spiked at 0.5 μg/g soil. Interference of soil matrix was not adequately removed by the addition of synthetic zeolite in extraction, although it reduced Ca2+ concentration. Ultrafiltration at 9 kDa after dilution of the soil extracts gave enough results to compare with those obtained by gas chromatography. It was suggested that overestimation in ELISA was caused by high-molecular-weight humus-like compounds in soil extracts.
    No preview · Article · Jan 2008 · Journal of Pesticide Science
  • [Show abstract] [Hide abstract]
    ABSTRACT: The tfdB gene encoding chlorophenol hydroxylase and its homolog were found in 2,4-dichlorophenoxyacetic acid (2,4-D)-degrading strain RD5-C2, which belongs to Bradyrhizobium sp. of alpha-Proteobacteria. The nucleotide and deduced amino acid sequence identities of the two genes, designated tfdBa and tfdBb, were 60% and 57% respectively. Their nucleotide sequences most closely matched those of previously reported tfdB, which consisted of those from 2,4-D-degrading beta- and gamma-Proteobacteria and Sphingomonas sp. in alpha-Proteobacteria, with 61-67% identity. The TfdBa expressed in Escherichia coli showed the highest activity for 2,4-dichlorophenol but a narrower range of activity for the other chlorophenols than previously reported TfdBs. In the case of TfdBb, however, no observable activity for any chlorophenols or phenol was detected, although production of a protein with an appropriate molecular size was observed. Based on codon usage patterns and the GC content of the genes, it probable that the tfdBa genes in the 2,4-D-degrading Bradyrhizobium sp. were obtained through horizontal gene transfer.
    No preview · Article · Aug 2007 · Bioscience Biotechnology and Biochemistry
  • Nguyen L. Huong · Kazuhito Itoh · Kousuke Suyama
    [Show abstract] [Hide abstract]
    ABSTRACT: Diverse 2,4-D and 2,4,5-T-degrading bacteria were isolated country-wide from ten Vietnamese soils, with or without a history of exposure to Agent Orange. The 353 degraders were phylogenetically grouped into three major categories; Burkholderias spp. (43.3% of all degraders), Sphingomonas spp. (40.2%), and Ralstonia spp. (15.3%) and two minor ones; Bradyrhizobium sp. (0.8%) and Nocardioides sp. (0.3%). The 2,4,5-T degraders, 65% of all degraders, were isolated from all soil samples and their 16S rRNA genes were the most homologous with that of Sphingomonas spp., Burkholderia spp. or Bradyrhizobium sp. The following four degradative genes were found by PCR: tfdA (tfdA alpha) in the Burkholderia spp., Ralstonia spp., Bradyrhizobium sp., and Nocardioides sp.; tfdB in all degraders; tftA (cadA) in the Sphingomonas spp., Burkholderia sp. and Bradyrhizobium sp.; tftC only in the Burkholderia sp. The degraders among Burkholderia spp. were isolated only from the central and southern sites, while those among Ralstonia spp. were found only at the north sites with one exception. The Sphingomonas spp. were isolated country-wide, but four phylogenetically different groups were found at one site, while only one group was found at the other five sites. At least three different plasmids that carried the tfd genes were found in the Burkholderia spp. and Ralstonia spp. without relation to the sites and the phylogenetic groups. These results suggest that the 2,4-D- and 2,4,5-T-degrading microbial consortia have spread countrywide and are diverse on a genetic as well as geographic basis.
    No preview · Article · Jan 2007 · Microbes and Environments
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The distribution of tfdAalpha and cadA, genes encoding 2,4-dichlorophenoxyacetate (2,4-D)-degrading proteins which are characteristic of the 2,4-D-degrading Bradyrhizobium sp. isolated from pristine environments, was examined by PCR and Southern hybridization in several Bradyrhizobium strains including type strains of Bradyrhizobium japonicum USDA110 and Bradyrhizobium elkanii USDA94, in phylogenetically closely related Agromonas oligotrophica and Rhodopseudomonas palustris, and in 2,4-D-degrading Sphingomonas strains. All strains showed positive signals for tfdAalpha, and its phylogenetic tree was congruent with that of 16S rRNA genes in alpha-Proteobacteria, indicating evolution of tfdAalpha without horizontal gene transfer. The nucleotide sequence identities between tfdAalpha and canonical tfdA in beta- and gamma-Proteobacteria were 46 to 57%, and the deduced amino acid sequence of TfdAalpha revealed conserved residues characteristic of the active site of alpha-ketoglutarate-dependent dioxygenases. On the other hand, cadA showed limited distribution in 2,4-D-degrading Bradyrhizobium sp. and Sphingomonas sp. and some strains of non-2,4-D-degrading B. elkanii. The cadA genes were phylogenetically separated between 2,4-D-degrading and nondegrading strains, and the cadA genes of 2,4-D degrading strains were further separated between Bradyrhizobium sp. and Sphingomonas sp., indicating the incongruency of cadA with 16S rRNA genes. The nucleotide sequence identities between cadA and tftA of 2,4,5-trichlorophenoxyacetate-degrading Burkholderia cepacia AC1100 were 46 to 53%. Although all root nodule Bradyrhizobium strains were unable to degrade 2,4-D, three strains carrying cadA homologs degraded 4-chlorophenoxyacetate with the accumulation of 4-chlorophenol as an intermediate, suggesting the involvement of cadA homologs in the cleavage of the aryl ether linkage. Based on codon usage patterns and GC content, it was suggested that the cadA genes of 2,4-D-degrading and nondegrading Bradyrhizobium spp. have different origins and that the genes would be obtained in the former through horizontal gene transfer.
    Full-text · Article · May 2004 · Applied and Environmental Microbiology
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The distribution of tfdAα and cadA, genes encoding 2,4-dichlorophenoxyacetate (2,4-D)-degrading proteins which are characteristic of the 2,4-D-degrading Bradyrhizobium sp. isolated from pristine environments, was examined by PCR and Southern hybridization in several Bradyrhizobium strains including type strains of Bradyrhizobium japonicum USDA110 and Bradyrhizobium elkanii USDA94, in phylogenetically closely related Agromonas oligotrophica and Rhodopseudomonas palustris, and in 2,4-D-degrading Sphingomonas strains. All strains showed positive signals for tfdAα, and its phylogenetic tree was congruent with that of 16S rRNA genes in α-Proteobacteria, indicating evolution of tfdAα without horizontal gene transfer. The nucleotide sequence identities between tfdAα and canonical tfdA in β- and γ-Proteobacteria were 46 to 57%, and the deduced amino acid sequence of TfdAα revealed conserved residues characteristic of the active site of α-ketoglutarate-dependent dioxygenases. On the other hand, cadA showed limited distribution in 2,4-D-degrading Bradyrhizobium sp. and Sphingomonas sp. and some strains of non-2,4-D-degrading B. elkanii. The cadA genes were phylogenetically separated between 2,4-D-degrading and nondegrading strains, and the cadA genes of 2,4-D degrading strains were further separated between Bradyrhizobium sp. and Sphingomonas sp., indicating the incongruency of cadA with 16S rRNA genes. The nucleotide sequence identities between cadA and tftA of 2,4,5-trichlorophenoxyacetate-degrading Burkholderia cepacia AC1100 were 46 to 53%. Although all root nodule Bradyrhizobium strains were unable to degrade 2,4-D, three strains carrying cadA homologs degraded 4-chlorophenoxyacetate with the accumulation of 4-chlorophenol as an intermediate, suggesting the involvement of cadA homologs in the cleavage of the aryl ether linkage. Based on codon usage patterns and GC content, it was suggested that the cadA genes of 2,4-D-degrading and nondegrading Bradyrhizobium spp. have different origins and that the genes would be obtained in the former through horizontal gene transfer.
    Full-text · Article · Apr 2004 · Applied and Environmental Microbiology