title: Physiological and genetic basis for self-aggregation of a thermophilic hydrogenotrophic methanogen, Methanothermobacter strain CaT2.
abstract: Several thermophilic hydrogenotrophic methanogens naturally aggregate in their habitats in association with hydrogen-producing bacteria for efficient transfer of the methane fermentation intermediates to produce methane. However, physiology of aggregation and the identity of aggregation-specific genes remain to be elucidated. Here, we isolated and characterized a hydrogen and formate-utilizing Methanothermobacter sp. CaT2 that is capable of self-aggregation and utilizing formate. CaT2 produced methane from propionate oxidation in association with a syntrophic propionate-oxidizing bacterium faster than other methanogens, including Methanothermobacter thermautotrophicus ΔH and Methanothermobacter thermautotrophicus Z-245. CaT2 also aggregated throughout the culture period and was coated with polysaccharides, which was not found on the ΔH and Z-245 cells. Sugar content (particularly of rhamnose and mannose) was also higher in the CaT2 cells than the ΔH and Z-245 cells. Comparative genomic analysis of CaT2 indicated that four candidate genes, all of which encode glycosyltransferase, were involved in aggregation of CaT2. Transcriptional analysis showed that one glycosyltransferase gene was expressed at relatively high levels under normal growth conditions. The polysaccharide layer on the CaT2 cell surface, which is probably assembled by these glycosyltransferases, may be involved in cell aggregation.
authors.affiliation: Department of Biological Chemistry, Faculty of Agriculture, Yamaguchi University, 1677-1 Yoshida, Yamaguchi, 753-8515, Japan; PRESTO, Japan Science and Technology Agency (JST), Kawaguchi, Saitama, 332-0012, Japan; Bioproduction Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, 305-8566, Japan.
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Kosaka
authors.forename: Hidehiro
authors.initials: H
authors.lastname: Toh
authors.forename: Asao
authors.initials: A
authors.lastname: Fujiyama
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Sakaki
authors.forename: Keiji
authors.initials: K
authors.lastname: Watanabe
authors.forename: Xian-Ying
authors.initials: XY
authors.lastname: Meng
authors.forename: Satoshi
authors.initials: S
authors.lastname: Hanada
authors.forename: Atsushi
authors.initials: A
authors.lastname: Toyoda
mesh_terms: D001422:Bacterial Adhesion / Q000235:genetics; D020869:Gene Expression Profiling; D005798:Genes, Bacterial; D016680:Genome, Bacterial; D006859:Hydrogen / Q000378:metabolism; D008697:Methane / Q000378:metabolism; D017013:Methanobacteriaceae / Q000302:isolation & purification / Q000502:physiology* / Q000648:ultrastructure; D009005:Monosaccharides / Q000378:metabolism; D010084:Oxidation-Reduction; D011422:Propionates / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D009005:Monosaccharides; D011422:Propionates; D006859:Hydrogen; D008697:Methane