Hanada, Satoshi

A novel aerobic, chemoheterotrophic bacterium, strain YO-36T, isolated from the rhizoplane of an aquatic plant (a reed, Phragmites australis) inhabiting a freshwater lake in Japan, was morphologically, physiologically and phylogenetically characterized. Strain YO-36T was Gram-negative and ovoid to rod-shaped, and formed pinkish hard colonies on agar plates. Strain YO-36T grew at 20–40 °C with optimum growth at 30–35 °C, whilst no growth was observed at 15 °C or 45 °C. The pH range for growth was 5.5–8.5 with an optimum at pH 6.5. Strain YO-36T utilized a limited range of substrates, such as sucrose, gentiobiose, pectin, gellan gum and xanthan gum. The strain contained C16 : 0, C16 : 1, C14 : 0 and C15 : 0 as the major cellular fatty acids and menaquinone-12 as the respiratory quinone. The G+C content of the genomic DNA was 62.4 mol%. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain YO-36T belonged to the candidate phylum OP10 comprised solely of environmental 16S rRNA gene clone sequences except for two strains, P488 and T49 isolated from geothermal soil in New Zealand; strain YO-36T showed less than 80 % sequence similarity to strains P488 and T47. Based on the phylogetic and phenotypic findings, a new genus and species, Armatimonas rosea gen. nov., sp. nov., is proposed for the isolate (type strain YO-36T  = NBRC 105658T  = DSM 23562T). In addition, a new bacterial phylum named Armatimonadetes phyl. nov. is proposed for the candidate phylum OP10 represented by A. rosea gen. nov., sp. nov. and Armatimonadaceae fam. nov., Armatimonadales ord. nov., and Armatimonadia classis nov.

One thermophilic (strain IMO-1T) and two mesophilic (strains KIBI-1T and YMTK-2T) non-spore-forming, non-motile, Gram-negative, multicellular filamentous micro-organisms, which were previously isolated as members of the tentatively named class ‘Anaerolineae’ of the phylum Chloroflexi, 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-1T, 0.4–0.5 μm for strain KIBI-1T and thinner than 0.2 μm for strain YMTK-2T. Strain IMO-1T could grow at pH 6.0–7.5 (optimum growth at pH 7.0). The optimal temperature for growth of strain IMO-1T was around 50 °C (growth occurred between 42 and 55 °C). Growth of the mesophilic strains KIBI-1T and YMTK-2T 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-1T, KIBI-1T and YMTK-2T were respectively 53.3, 59.5 and 48.2 mol%. Major fatty acids for thermophilic strain IMO-1T were anteiso-C17 : 0, iso-C15 : 0, C16 : 0 and anteiso-C15 : 0, whereas those for mesophilic strains KIBI-1T and YMTK-2T were branched C14 : 0, iso-C15 : 0, C16 : 0 and branched C17 : 0, and branched C17 : 0, C16 : 0, C14 : 0 and C17 : 0, respectively. Detailed phylogenetic analyses based on their 16S rRNA gene sequences indicated that the isolates belong to the class-level taxon ‘Anaerolineae’ of the bacterial phylum Chloroflexi, 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 Chloroflexi. Here, Anaerolinea thermolimosa sp. nov. (type strain IMO-1T=JCM 12577T=DSM 16554T), Levilinea saccharolytica gen. nov., sp. nov. (type strain KIBI-1T=JCM 12578T=DSM 16555T) and Leptolinea tardivitalis gen. nov., sp. nov. (type strain YMTK-2T=JCM 12579T=DSM 16556T) are proposed. In addition, we formally propose to subdivide the tentative class-level taxon ‘Anaerolineae’ into Anaerolineae classis nov. and Caldilineae classis nov. We also propose the subordinate taxa Anaerolineales ord. nov., Caldilineales ord. nov., Anaerolineaceae fam. nov. and Caldilineaceae fam. nov.