No abstract

Molecular surveys of aphotic habitats have indicated the presence of major uncultured lineages phylogenetically classified as members of the Cyanobacteria. One of these lineages has recently been proposed as a nonphotosynthetic sister phylum to the Cyanobacteria, the Melainabacteria, based on recovery of population genomes from human gut and groundwater samples. Here, we expand the phylogenomic representation of the Melainabacteria through sequencing of six diverse population genomes from gut and bioreactor samples supporting the inference that this lineage is nonphotosynthetic, but not the assertion that they are strictly fermentative. We propose that the Melainabacteria is a class within the phylogenetically defined Cyanobacteria based on robust monophyly and shared ancestral traits with photosynthetic representatives. Our findings are consistent with theories that photosynthesis occurred late in the Cyanobacteria and involved extensive lateral gene transfer and extends the recognized functionality of members of this phylum.

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.

Techno I og y, Tsu k u ba , lbaraki 305-8566, Japan ~~ The microbial diversity of two types of methanogenic granular sludge, mesophilic (35 "C) and thermophilic (55 "C), which had been treating sucrose/propionate/acetate-based artificial wastewater were compared. 16s rDNA clone libraries were constructed by PCR with a prokaryote-specific primer set, and partial sequencing of the clonal 165 rDNAs was conducted for phylogenetic analysis. Of 11 5 mesophilic granule and 110 thermophilic granule clones sequenced, 19 and 22 %, respectively, were phylogenetically affiliated with the domain Archaea, and the remainder in each case were assigned to the domain Bacteria. Within the domain Archaea, the 165 rDNA clones in both libraries showed relatively close relationships with those of methanogens. Within the Bacteria, a major group represented in the mesophilic clone library was the delta subclass of the Proteobacteria (27%), in which high degrees of relatedness were observed between the clonal 165 rDNA sequences and those of previously identified syntrophic bacteria and sulfate-reducing bacteria. In contrast, in the thermophilic clone library, the Thermodesulfovibrio group (19%), the green non-sulfur bacteria (18%) and the low G+C subclass of the Gram-positive bacteria (18 %) were predominant. A significant difference between the two libraries was that no clone affiliated with the Proteobacteria was detected in the thermophilic clone library, whereas the Proteobacteria was the most predominant group in the mesophilic clones. Thirty-six and 24 different sequences were found in the mesophilic and thermophilic clones, respectively, suggesting that the microbial diversity of the thermophilic granule was lower than that of the mesophilic granule.