1887

Abstract

One thermophilic (strain IMO-1) and two mesophilic (strains KIBI-1 and YMTK-2) non-spore-forming, non-motile, Gram-negative, multicellular filamentous micro-organisms, which were previously isolated as members of the tentatively named class ‘’ of the phylum , were characterized. All isolates were strictly anaerobic micro-organisms. The length of the three filamentous isolates was greater than 100 μm and the width was 0.3–0.4 μm for strain IMO-1, 0.4–0.5 μm for strain KIBI-1 and thinner than 0.2 μm for strain YMTK-2. Strain IMO-1 could grow at pH 6.0–7.5 (optimum growth at pH 7.0). The optimal temperature for growth of strain IMO-1 was around 50 °C (growth occurred between 42 and 55 °C). Growth of the mesophilic strains KIBI-1 and YMTK-2 occurred at pH 6.0–7.2 with optimal growth at pH 7.0. Both of the mesophilic strains were able to grow in a temperature range of 25–50 °C with optimal growth at around 37 °C. Yeast extract was required for growth of all three strains. All the strains could grow with a number of carbohydrates in the presence of yeast extract. The G+C contents of the DNA of strains IMO-1, KIBI-1 and YMTK-2 were respectively 53.3, 59.5 and 48.2 mol%. Major fatty acids for thermophilic strain IMO-1 were anteiso-C, iso-C, C and anteiso-C, whereas those for mesophilic strains KIBI-1 and YMTK-2 were branched C, iso-C, C and branched C, and branched C, C, C and C, respectively. Detailed phylogenetic analyses based on their 16S rRNA gene sequences indicated that the isolates belong to the class-level taxon ‘’ of the bacterial phylum , which for a long time had been considered as a typical uncultured clone cluster. Their morphological, physiological, chemotaxonomic and genetic traits strongly support the conclusion that these strains should be described as three novel independent taxa in the phylum . Here, sp. nov. (type strain IMO-1=JCM 12577=DSM 16554), gen. nov., sp. nov. (type strain KIBI-1=JCM 12578=DSM 16555) and gen. nov., sp. nov. (type strain YMTK-2=JCM 12579=DSM 16556) are proposed. In addition, we formally propose to subdivide the tentative class-level taxon ‘’ into classis nov. and classis nov. We also propose the subordinate taxa ord. nov., ord. nov., fam. nov. and fam. nov.

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2006-06-01
2019-12-06
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