Journal of Microbiology

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Aliisedimentitalea scapharcae gen. nov., sp. nov., isolated from ark shell Scapharca broughtonii: Young-Ok Kim , Sooyeon Park , Bo-Hye Nam , Dong-Gyun Kim , Sung-Min Won , Ji-Min Park , Jung-Hoon Yoon; J. Microbiol. 2015;53(8):495-502. Published online July 31, 2015; DOI: https://doi.org/10.1007/s12275-015-5075-7

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Abstract: A Gram-negative, aerobic, non-spore-forming, motile and ovoid or rod-shaped bacterial strain, designated MA2-16T, was isolated from ark shell (Scapharca broughtonii) collected from the South Sea, South Korea. Strain MA2-16T was found to grow optimally at 30캜, at pH 7.0?.0 and in the presence of 2.0% (w/v) NaCl. Neighbour-joining, maximum-likelihood and maximum-parsimony phylogenetic trees based on 16S rRNA gene sequences revealed that strain MA2-16T clustered with the type strain of Sedimentitalea nanhaiensis. The novel strain exhibited a 16S rRNA gene sequence similarity value of 97.1% to the type strain of S. nanhaiensis. In the neighbour- joining phylogenetic tree based on gyrB sequences, strain MA2-16T formed an evolutionary lineage independent of those of other taxa. Strain MA2-16T contained Q-10 as the predominant ubiquinone and C18:1 ?c and 11-methyl C18:1 ?c as the major fatty acids. The major polar lipids of strain MA2-16T were phosphatidylcholine, phosphatidylglycerol, phosphatidylethanolamine, an unidentified aminolipid and an unidentified lipid. The DNA G+C content of strain MA2- 16T was 57.7 mol% and its DNA-DNA relatedness values with the type strains of S. nanhaiensis and some phylogenetically related species of the genera Leisingera and Phaeobacter were 13?4%. On the basis of the data presented, strain MA2-16T is considered to represent a novel genus and novel species within the family Rhodobacteraceae, for which the name Aliisedimentitalea scapharcae gen. nov., sp. nov. is proposed. The type strain is MA2-16T (=KCTC 42119T =CECT 8598T).

NOTE] Probing the ArcA Regulon in the Rumen Bacterium Mannheimia succiniciproducens by Genome-Wide Expression Profiling: Seulgi Yun , Jong Moon Shin , Oh-Cheol Kim , Young Ryul Jung , Doo-Byoung Oh , Sang Yup Lee , Ohsuk Kwon; J. Microbiol. 2012;50(4):665-672. Published online July 21, 2012; DOI: https://doi.org/10.1007/s12275-012-2007-7

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Abstract: In this study, the putative target genes of the Arc two-component system of the rumen bacterium Mannheimia succiniciproducens were determined by analyzing the transcriptome of the ArcA overexpression strain and by the in silico scanning of the entire genome sequence with the position weight matrix of the ArcA binding sequence developed for Escherichia coli. The majority of 79 repressed genes were involved in energy metabolism and carbohydrate transport and metabolism, while the majority of 82 induced genes were involved in hypothetical or unknown functions. Our results suggest that the Arc system in M. succiniciproducens has a specific function that differs from that in E. coli.

Purification and Biochemical Properties of a Glucose-Stimulated β-D-Glucosidase Produced by Humicola grisea var. thermoidea Grown on Sugarcane Bagasse: Cesar Vanderlei Nascimento , Flávio Henrique Moreira Souza , Douglas Chodi Masui , Francisco Assis Leone , Rosane Marina Peralta , João Atílio Jorge , Rosa Prazeres Melo Furriel; J. Microbiol. 2010;48(1):53-62. Published online March 11, 2010; DOI: https://doi.org/10.1007/s12275-009-0159-x

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Abstract: The effect of several carbon sources on the production of mycelial-bound β-glucosidase by Humicola grisea var. thermoidea in submerged fermentation was investigated. Maximum production occurred when cellulose was present in the culture medium, but higher specific activities were achieved with cellobiose or sugarcane bagasse. Xylose or glucose (1%) in the reaction medium stimulated β-glucosidase activity by about 2-fold in crude extracts from mycelia grown in sugarcane bagasse. The enzyme was purified by ammonium sulfate precipitation, followed by Sephadex G-200 and DEAE-cellulose chromatography, showing a single band in PAGE and SDS-PAGE. The β-glucosidase had a carbohydrate content of 43% and showed apparent molecular masses of 57 and 60 kDa, as estimated by SDS-PAGE and gel filtration, respectively. The optimal pH and temperature were 6.0 and 50°C, respectively. The purified enzyme was thermostable up to 60 min in water at 55°C and showed half-lives of 7 and 14 min when incubated in the absence or presence of 50 mM glucose, respectively, at 60°C. The enzyme hydrolyzed p-nitrophenyl-β-D-glucopyranoside, p-nitrophenyl-β-galactopyranoside, p-nitrophenyl-β-D-fucopyranoside, p-nitrophenyl-β-D-xylopyranoside, o-nitrophenyl-β-Dgalactopyranoside, lactose, and cellobiose. The best synthetic and natural substrates were p-nitrophenyl-β-Dfucopyranoside and cellobiose, respectively. Purified enzyme activity was stimulated up to 2-fold by glucose or xylose at concentrations from 25 to 200 mM. The addition of purified or crude β-glucosidase to a reaction medium containing Trichoderma reesei cellulases increased the saccharification of sugarcane bagasse by about 50%. These findings suggest that H. grisea var. thermoidea β-glucosidase has a potential for biotechnological applications in the bioconversion of lignocellulosic materials.

NOTE] Evidence Against the Physiological Role of Acetyl Phosphate in the Phosphorylation of the ArcA Response Regulator in Escherichia coli: Xueqiao Liu , Gabriela R. Peña Sandoval , Barry L. Wanner , Won Seok Jung , Dimitris Georgellis , Ohsuk Kwon; J. Microbiol. 2009;47(5):657-662. Published online October 24, 2009; DOI: https://doi.org/10.1007/s12275-009-0087-9

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Abstract: The Arc two-component signal transduction system of Escherichia coli comprises the ArcB sensor kinase and the ArcA response regulator. Under anoxic growth conditions, ArcB autophosphorylates and transphosphorylates ArcA, which, in turn, represses or activates its target operons. ArcA has been shown to be able to autophosphorylate in vitro at the expense of acetyl-P. Here, the in vivo effect of acetyl phosphate on the redox signal transduction by the Arc system was assessed. Our results indicate that acetyl phosphate can modulate the expression of ArcA-P target genes only in the absence of ArcB. Therefore, the acetyl phosphate dependent ArcA phosphorylation route does not seem to play a significant role under physiological conditions.

Polyamine Stimulation of arcA Expression in Escherichia coli: Mun Su Rhee , Young Sik Kim , Seon Young Park , Myung Hun Choi , Bo Min Kim , Seong Uk Kang , Kui Joo Lee , Jong Ho Lee; J. Microbiol. 2002;40(4):305-312.

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Abstract: The effects of two natural polyamines (putrescine and spermidine) on the synthesis of ArcA, a response regulator of the Arc two-component signal transduction system, were studied using an E. coli mutant deficient in polyamine biosynthesis. Endogenous polyamine deficiency of the mutant resulted in marked reduction in the ArcA level determined by Western blot analysis. Putrescine supplement to the growth medium effectively increased the ArcA level of the mutant in a concentration-dependent manner. Spermidine also stimulated the ArcA level in the mutant to a greater degree than putrescine. Expression of arcA'::lacZ operon fusion in the mutant was stimulated 6-fold and 10-fold by putrescine and spermidine at a 1mM concentration, respectively, indicating that the stimulatory effect of the polyamines on ArcA synthesis is due to transcriptional induction, and that spermidine is a more potent arcA inducer than putrescine. The polyamine-dependent arcA'::lacZ induction was growth-phase-dependent and independent of either arcA or fnr which are two regulators involved in anaerobic stimulation of the ArcA level. These results suggested that putrescine and spermidine polyamines may be potential intracellular signal molecules in the control of arcA expression, and thereby may play an important role in cellular metabolism.

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