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839 results on '"Igarashi, Yasuo"'

225. Reduction of Fe( III) oxides by phylogenetically and physiologically diverse thermophilic methanogens.

Author

Yamada, Chihaya, Kato, Souichiro, Kimura, Satoshi, Ishii, Masaharu, and Igarashi, Yasuo

Subjects
IRON oxides, PHYLOGENY, METHANOGENS, THERMOPHILIC bacteria, METHANOSARCINA thermophila, CELL membranes
Abstract

Three thermophilic methanogens ( Methanothermobacter thermautotrophicus, Methanosaeta thermophila, and Methanosarcina thermophila) were investigated for their ability to reduce poorly crystalline Fe( III) oxides (ferrihydrite) and the inhibitory effects of ferrihydrite on their methanogenesis. This study demonstrated that Fe( II) generation from ferrihydrite occurs in the cultures of the three thermophilic methanogens only when H2 was supplied as the source of reducing equivalents, even in the cultures of Mst. thermophila that do not grow on and produce CH4 from H2/ CO2. While supplementation of ferrihydrite resulted in complete inhibition or suppression of methanogenesis by the thermophilic methanogens, ferrihydrite reduction by the methanogens at least partially alleviates the inhibitory effects. Microscopic and crystallographic analyses on the ferrihydrite-reducing Msr. thermophila cultures exhibited generation of magnetite on its cell surfaces through partial reduction of ferrihydrite. These findings suggest that at least certain thermophilic methanogens have the ability to extracellularly transfer electrons to insoluble Fe( III) compounds, affecting their methanogenic activities, which would in turn have significant impacts on materials and energy cycles in thermophilic anoxic environments. [ABSTRACT FROM AUTHOR]

Published
2014
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226. Stabilization of Pseudomonas aeruginosa Cytochromec 551 by Systematic Amino Acid Substitutions Based on the Structure of Thermophilic Hydrogenobacter thermophilus Cytochrome c 552

Author

Hasegawa, Jun, primary, Shimahara, Hideto, additional, Mizutani, Masayuki, additional, Uchiyama, Susumu, additional, Arai, Hiroyuki, additional, Ishii, Masaharu, additional, Kobayashi, Yuji, additional, Ferguson, Stuart J., additional, Sambongi, Yoshihiro, additional, and Igarashi, Yasuo, additional

Published
1999
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247. The changes of microbial abundance and functional genes in bioelectrochemistry at 15 ℃.

Author

Wang, Hui, Zeng, Shufang, Du, Hongxia, Xie, Haiying, Igarashi, Yasuo, and Luo, Feng

Subjects
BIOELECTROCHEMISTRY, ELECTRON transport, METABOLITES, CHARGE exchange, ANAEROBIC digestion, CARBON electrodes, BIOACCUMULATION, ACETATES
Abstract

Bioelectrochemistry system (BES) provides a new strategy for the improvement of low temperature anaerobic digestion (AD) for methane production. In this study, the BES with carbon brushes as electrodes was operated at 15 °C to analyze the changes of microbial abundance and functional genes. The microbial community structure showed that the application of voltage had no effect to type and relative abundance of bacteria based on 16S-rRNA sequencing. Metatranscriptomic analyses revealed that significantly enhanced the abundance of fermentation bacteria in the fluid activated sludge, and the relative abundance of biosynthesis of other secondary metabolites (61.56%) was also highly expressed. More than that, the abundance of electricigens (Pseudomonas , Syntrophomonas) was also enriched in the BES system. These electricigens could interact with methanogens to promote electron transfer by direct interspecies electron transfer (DIET). The expression level of functional enzyme related to electron transport was increased at the anode (30.60%), but decreased at the cathode (−33.84%). Analysis of methanogens found that the application of voltage decreased the relative abundance of Methanosarcina and promoted the enrichment of Methanothrix. At 15 ℃, acetoclastic was the mainly methanogenic pathway. What's more, the application of voltage could enhance the acetoclastic and inhibited the hydrogenotrophic and the methylotrophic pathway. Further, the acetoclastic pathway was changed from acetate kinase (EC: 2.7.2.1) and phosphate acetyltransferase (EC: 2.3.1.8) to acetate-CoA ligase (EC: 6.2.1.1) by applied voltage. These results are conducive to the further development of low-temperature AD treatment technology. [Display omitted] • Methahnosarcina and Methanothrix were dominated in DNC and SC reactor, respectively. • The applied voltage increased the abundance of electroactive microorganisms. • The application of voltage promoted the acetoclastic pathway at low temperature. • The SC reactor achieved acetate to acetyl-CoA by acetate-CoA ligase. • The DNC reactor was through acetate kinase and phosphate acetyltransferase. [ABSTRACT FROM AUTHOR]

Published
2022
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