This is the first report on comparative analysis of the genomes of phototrophic Chloroflexota. A mesophilic filamentous anoxygenic phototrophic bacterium, designated M50-1, was isolated from a microbial mat of the Chukhyn Nur soda lake (northeastern Mongolia) with salinity of 5−14 g/L and pH 8.0−9.3. The organism is a strictly anaerobic phototrophic bacterium, which required sulfide for phototrophic growth. The cells formed short undulate trichomes surrounded by a thin sheath and containing gas vesicles. Motility of the trichomes was not observed. The cells contained chlorosomes. The antenna pigments were bacteriochlorophyll d and β- and γ -carotenes. Analysis of the genome assembled from the metagenome of the enrichment culture revealed all the enzymes of the 3-hydroxypropionate bi-cycle for autotrophic CO2 assimilation. The genome also contained the genes encoding a type IV sulfide:quinone oxidoreductase (sqrX). The organism had no nifHDBK genes, encoding the proteins of the nitrogenase complex responsible for dinitrogen fixation. Classification of the filamentous anoxygenic phototrophic bacterium M50-1 as a new ‘Candidatus Chloroploca’ species was proposed, with the species name ‘Candidatus Chloroploca mongolica’ sp. nov.
Our results significantly improved our understanding of the biodiversity and genomics of the phototrophic filamentous anoxygenic phototrophs of the phylum Chloroflexota. It may be concluded that genetic and phenotypic research on the enrichment cultures of mesophilic FAP from diverse sources show the new trends in the evolution of chlorophototrophs.
The SciBear team is proud to have participated in this unique research project. Our contribution was comparative genomic analyses of Chlroroflexota genomes, including metagenomic, phylogenetic and pan-genome approaches.
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FEMS Microbiology Letters. 2021. doi:10.1093/femsle/fnab107