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Chlorobaculum macestae sp. nov., a new green sulfur bacterium

Keppen, O. I., Berg, I. A., Lebedeva, N. V., Taisova, A. S., Kolganova, T. V., Slobodova, N. V., Bulygina, E. S., Tourova, T. P., Ivanovsky, R. N.
Microbiology 2008 v.77 no.1 pp. 69-77
Chlorobium, DNA, Gram-negative bacteria, amino acid composition, amino acid sequences, carbon, carotenoids, casein hydrolysates, cell walls, coasts, genes, hydrogen, new species, nitrogen, nucleotide sequences, pH, phylogeny, pigments, ribosomal RNA, sodium chloride, sulfur, sulfur springs, temperature, thiosulfates, urea, vitamin B12, Black Sea
The investigated green sulfur bacterium, strain M, was isolated from a sulfidic spring on the Black Sea Coast of the Caucasus. The cells of strain M are straight or curved rods 0.6-0.9 × 1.8-4.2 μm in size. According to the cell wall structure, the bacteria are gram-negative. Chlorosomes are located along the cell periphery. Strain M is an obligate anaerobe capable of photoautotrophic growth on sulfide, thiosulfate, and H₂. Acetatate is utilized as an additional carbon source. It utilizes ammonium, urea, casein hydrolysate, and N₂ as nitrogen sources and sulfide, thiosulfate, and elemental sulfur as sulfur sources. Bacteriochlorophyll c and the carotenoid chlorobactene are the main pigments. The optimal growth temperature is 25-28°C; the optimal pH is 6.8. The strain does not require NaCl. Vitamin B 12 stimulates growth. The content of the G+C base pairs in the DNA of strain M is 58.3 mol %. In the phylogenetic tree constructed on the basis of analysis of nucleotide sequences of 16S rRNA genes, strain M forms a separate branch, which occupies an intermediate position between the phylogenetic cluster containing representatives of the genus Chlorobaculum (94.9-96.8%) and the cluster containing species of the genus Chlorobium (94.1-96.5%). According to the results of analysis of the amino acid sequence corresponding to the fmo gene, strain M represents a branch which, unlike that in the “ribosomal” tree, falls into the cluster of the genus Chlorobaculum (95.8-97.2%). Phylogenetic analysis of the amino acid sequence corresponding to the nifH gene placed species of the genera Chlorobaculum and Chlorobium into a single cluster, whereas strain M formed a separate branch. The results obtained allow us to describe strain M as a new species of the genus ChlorobacChlorobaculum -- Chlorobaculum macestae sp. nov.