The Journal of General and Applied Microbiology
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Volume 57 , Issue 6
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  • Sho-ichi Tsujiyama, Hitomi Ueno
    Volume 57 (2011) Issue 6 Pages 309-317
    Released: February 21, 2012
    JOURNALS FREE ACCESS
    To develop enzyme preparations capable of digesting plant biomass, we examined the production of cinnamic acid esterase as well as cellulolytic and xylanolytic enzymes in cultures of Schizophyllum commune. The cinnamic acid esterase was produced in the cultures containing solid cellulosic substrates, with production being enhanced by delignifying the wood powder. This indicates that these esterases are produced by cellulose, despite their substrates being phenolic compounds. Cellulolytic and xylanolytic enzymes, with the exception of α-arabinofuranosidase, were also produced in cultures containing cellulosic substances. These results show that enzyme preparation can have high activity of cinnamic acid esterase and cellulolytic and xylanolytic enzymes when S. commune is incubated in the presence of cellulose. These enzyme preparations will be useful for digesting plant biomass and for releasing cinnamic acid derivatives from plant cell walls.
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  • Ya Wen, Juan Zhang, Qiuxiang Yan, Shunpeng Li, Qing Hong
    Volume 57 (2011) Issue 6 Pages 319-329
    Released: February 21, 2012
    JOURNALS FREE ACCESS
    Strain F11T, a phenanthrene-degrading bacterium, was isolated from a petroleum residue treatment system, and classified under the genus Rhizobium based on the similarity analysis of its 16S rRNA and recA gene sequences. Strain F11T falls into the same phylogenetic clade with Rhizobium oryzae Alt 505T (96.8% 16S rRNA gene sequence similarity) and Rhizobium pseudoryzae J34A-127T (96.2%). Major cellular fatty acids of strain F11T are C16:0 (6.24%) and summed feature 8 (C18:1ω7c and/or C18:1ω6c, 76.59%), which are also the major fatty acids of R. oryzae Alt 505T and R. pseudoryzae J34A-127T. The DNA G+C content of strain F11T was 59.3±0.4 mol%. Based on the phylogenetic analysis as well as biochemical and physiological characteristics, strain F11T could be separated from all recognized Rhizobium species. Strain F11T (=DSM 21882T =CCTCC AB 209029T) was considered to be representative of a novel species of Rhizobium, for which the name Rhizobium phenanthrenilyticum sp. nov. is proposed.
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  • Tadayuki Tsukatani, Hikaru Suenaga, Tomoko Higuchi, Masanobu Shiga, Ka ...
    Volume 57 (2011) Issue 6 Pages 331-339
    Released: February 21, 2012
    JOURNALS FREE ACCESS
    Bacteria are fundamentally divided into two groups: Gram-positive and Gram-negative. Although the Gram stain and other techniques can be used to differentiate these groups, some issues exist with traditional approaches. In this study, we developed a method for differentiating Gram-positive and -negative bacteria using a colorimetric microbial viability assay based on the reduction of the tetrazolium salt {2-(2-methoxy-4-nitrophenyl)-3-(4-nitrophenyl)-5-(2,4-disulfophenyl)-2H-tetrazolium, monosodium salt} (WST-8) via 2-methyl-1,4-napthoquinone with a selection medium. We optimized the composition of the selection medium to allow the growth of Gram-negative bacteria while inhibiting the growth of Gram-positive bacteria. When the colorimetric viability assay was carried out in a selection medium containing 0.5μg/ml crystal violet, 5.0 μg/ml daptomycin, and 5.0μg/ml vancomycin, the reduction in WST-8 by Gram-positive bacteria was inhibited. On the other hand, Gram-negative bacteria produced WST-8-formazan in the selection medium. The proposed method was also applied to determine the Gram staining characteristics of bacteria isolated from various foodstuffs. There was good agreement between the results obtained using the present method and those obtained using a conventional staining method. These results suggest that the WST-8 colorimetric assay with selection medium is a useful technique for accurately differentiating Gram-positive and -negative bacteria.
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  • Sang-Rae Kim, Yeon-Ju Kim, Ngoc-Lan Nguyen, Jin-Woo Min, Ji-Na Jeon, D ...
    Volume 57 (2011) Issue 6 Pages 341-346
    Released: February 21, 2012
    JOURNALS FREE ACCESS
    A novel strain of Flavobacterium, DCY55T, a Gram-negative, yellow-pigmented, rod-shaped, non-spore-forming and gliding-motile bacterium, was isolated from the soil of a ginseng field in South Korea. Phylogenetic analysis, based on the 16S rRNA sequence, demonstrated that strain DCY55T belongs to the genus Flavobacterium within the family Flavobacteriaceae. Strain DCY55T showed the highest similarity with F. johnsoniae UW101T (97.1%), F. ginsenosidimutans THG 01T (96.8%), F. defluvii EMB 117T (96.6%), F. banpakuense 15F3T (96.3%) and F. anhuiense D3T (95.8%). Chemotaxonomic results showed that strain DCY55T predominantly contains menaquinone MK-6, that its DNA G+C content is 36.1mol%, and that its major cellular fatty acids are iso-C15:0, summed feature 3 (comprising iso-C15:0 2-OH and/or C16:1 ω 7c) and C16:0. The chemotaxonomic and genotypic characteristics support the taxonomic classification of strain DCY55T to the genus Flavobacterium. The results of physiological and biochemical tests confirmed that strain DCY55T is distinct from previously validated species. We conclude that strain DCY55T should be classified as a novel species of the genus Flavobacterium, for which the name Flavobacterium ginsengiterrae sp. nov. is proposed, with the type strain DCY55T (=KCTC 23319T = JCM 17337T).
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  • Khalid A. Hussein, Sedky H. A. Hassan, Jin Ho Joo
    Volume 57 (2011) Issue 6 Pages 347-355
    Released: February 21, 2012
    JOURNALS FREE ACCESS
    In this study Beauveria bassiana and Metarhizium anisopliae were used as inexpensive and efficient biosorbents for Pb(II) and Cd(II) from aqueous metal solutions. The effects of various physicochemical factors on Pb(II) and Cd(II) biosorption by B. bassiana and M. anisopliae were studied. The optimum pH for Cd(II) and Pb(II) biosorption by two fungal species was achieved at pH 6.0 for Pb(II) and 5.0 Cd(II) at a constant time of 30min. The nature of fungal biomass and metal ion interactions was evaluated by Fourier transform infrared. The maximum adsorption capacities (qmax) calculated from Langmuir isotherms for Pb(II), and Cd(II) uptake by B. bassiana were 83.33±0.85, and 46.27±0.12 mg/g, respectively. However, the qmax obtained for Pb(II) uptake by M. anisopliae was 66.66±0.28 mg/g, and 44.22±0.13 mg/g for Cd(II). B. bassiana showed higher adsorption capacity compared to M. anisopliae. The data obtained imply the potential role of B. bassiana and M. anisopliae for heavy metal removal from aqueous solutions.
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  • Young-Ok Kim, In-Suk Park, Hyung-Kwou Kim, Bo-Hye Nam, Hee Jeong Kong, ...
    Volume 57 (2011) Issue 6 Pages 357-364
    Released: February 21, 2012
    JOURNALS FREE ACCESS
    Salinisphaera sp. P7-4 was isolated from the intestine of silver whiting, Sillago japonicas caught in the Pacific Ocean, and the esterase gene was cloned using the shotgun method. The amino acid sequence deduced from the nucleotide sequence (951 bp) corresponded to a protein of 316 amino acid residues with a molecular weight of 34,443. The esterase had 46 and 44% identities with the esterase enzymes of Ralstonia eutropha JMP134 and Rhodopseudomonas palustris HaA2, respectively. The primary structure of P7-4 esterase showed the conserved catalytic triad (Ser, Asp, His), consensus pentapeptide GXSXG, and oxyanion hole sequence (HG). The protein P7-4 was successfully expressed in Escherichia coli in a biologically active form. The enzyme showed high catalytic activity at low temperatures (5-25° C) with an activation energy of 2.18 kcal/mol. This result indicated that the esterase from Salinisphaera sp. P7-4 is a new cold-adapted enzyme. The enzyme preferentially hydrolyzed acyl-group chains with short chain lengths of ≤10 carbon. Metal ions such as Cd2+, Co2+, Cu2+, Hg2+, Ni2+ and Zn2+ inhibited enzymatic activity. Additionally, EDTA has no effect on its activity, whereas inhibition was observed with PMSF, a serine hydrolase inhibitor.
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  • Sirikhwan Tinrat, Sumarn Saraya, Mullika Traidej Chomnawang
    Volume 57 (2011) Issue 6 Pages 365-378
    Released: February 21, 2012
    JOURNALS FREE ACCESS
    Researchers are becoming more interested in studying probiotics at present due to their benefit to human and animal health. In this study, newly isolated strains from human feces were evaluated for probiotic properties. A total of sixty isolated strains were collected from feces and six out of sixty isolated strains could inhibit the growth of Salmonella typhi and Salmonella typhimurium. The strain which gave the best inhibitory effect was selected for further characterization as a probiotic strain. The identification of this strain was analyzed on the basis of morphological and biochemical characteristics and 16S rDNA gene sequence. This strain was Gram-positive, rod shaped, and catalase and oxidase-negative, and produced acids from D-glucose, D-fructose, lactose, mannitol, sorbitol, inulin and starch. It could not hydrolyze esculin or red blood cells. Based on its 16S rDNA gene sequence, it was Lactobacillus salivarius, and so was called L. salivarius MTC 1026 in this study, and was closely related with L. salivarius DSPV 344T isolated from the calf gut. It was able to survive in gastric and small intestinal juices at pH 2.0 and 1.0% bile salt for several hours and also could grow at 45°C. Moreover, this strain showed inhibitory activity against a variety of food-borne pathogens. It was highly sensitive to piperacillin, chloramphenicl, ampicillin, erythromycin and ceftazidime. After plasmid curing, this strain was susceptible to gentamicin, amikacin, norfloxacin and ciprofloxacin. L. salivarius MTC 1026 could significantly inhibit the adhesion process of E. coli ATCC 25922 and S. typhimurium ATCC 13311 on Caco-2 monolayers in a competition assay and also reduced invasion of both pathogens (4-log cfu/ml) in an exclusion and displacement assay. Therefore, it was clearly demonstrated in this study that L. salivarius MTC 1026 has shown promising properties as a candidate for a potential probiotic for applications in humans and animals.
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  • Bo Yang, Zhigang Liu, Bei Deng, Yulei Zeng, Jiajun Hu, Weilin Li, Zhen ...
    Volume 57 (2011) Issue 6 Pages 379-386
    Released: February 21, 2012
    JOURNALS FREE ACCESS
    Microorganisms able to bioconvert DL-2-amino-Δ2-thiazoline-4-carboxylic acid (DL-ATC) into L-cysteine were originally isolated from 10 soil samples with DL-ATC as the sole nitrogen source. Ninety-seven L-cysteine-producing bacterial strains were screened out and obtained in pure culture. Among them, a strain, designated as HUT-78, was selected as the best producer, with a molar bioconversion rate of 60%. Based on the 16S rRNA gene sequence analysis, this isolate was placed within the genus Pseudomonas. A novel mutant of this strain with a significantly reduced activity of L-cysteine desulfhydrase, a L-cysteine-decomposing enzyme, was derived by UV-mutagenesis. This mutant, designated as mHUT-78, exhibited a 42% increase in L-cysteine producing activity. Moreover, the bioconversion reactions in both the parent and the mutant strain were significantly accelerated by co-overexpression of the two key enzymes, AtcB and AtcC, involved in the bioconversion reaction.
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