Anaerolinea thermophila gen. nov., sp. nov. and Caldilinea aerophila gen. nov., sp. nov., novel filamentous thermophiles that represent a previously uncultured lineage of the domain bacteria at the subphylum level

Two thermophilic, Gram-negative, non-spore-forming, multicellular filamentous micro-organisms were isolated from thermophilic granular sludge in an upflow anaerobic sludge blanket reactor treating fried soybean-curd manufacturing waste water (strain UNI-1^T) and from a hot spring sulfur-turf in Japan (strain STL-6-O1^T). The filaments were longer than 100 μm and of 0.2-0.3 μm (strain UNI-1^T) or 0.7-0.8 μm (strain STL-6-O1^T) in width. Strain UNI-1^T was a strictly anaerobic organism. The optimum temperature for growth was around 55 °C; growth occurred in the range 50-60 °C. The optimum pH for growth was around 7.0; growth occurred in the range pH 6.0-8.0. Strain STL-6-O1^T was a facultatively aerobic bacterium. The optimum temperature for growth was around 55 °C; growth occurred in the range 37-65 °C. The optimum pH for growth was around 7.5-8.0; growth occurred in the range pH 7.0-9.0. The two organisms grew chemo-organotrophically on a number of carbohydrates and amino acids in the presence of yeast extract. The G + C content of the DNA of strains UNI-1^T and STL-6-O1^T was 54.5 and 59.0 mol%, respectively. Major cellular fatty acids for strain UNI-1^T were C_16:0, C_15:0, C_14:0, and C_18:0, whereas those for strain STL-6-O1^T were C_18:0, C_16:0, C_17:0 and iso-C_17:0. MK-10 was the major quinone from aerobically grown STL-6-O1^T cells. Phylogenetic analyses based on 16S rDNA sequences revealed that both strains belong to an uncultured, previously recognized clone lineage of the phylum Chloroflexi (formerly known as green non-sulfur bacteria). These phenotypic and genetic properties suggested that each strain should be classified into a new independent genus; hence, the names Anaerolinea thermophila and Caldilinea aerophila are proposed for strains UNI-1^T (=JCM 11387^T = DSM 14523^T) and STL-6-O1^T(=JCM 11388^T = DSM 14525^T), respectively. These strains represent the type and sole species of the genera Anaerolinea and Caldilinea, respectively.