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Abstract
A Gram-stain-negative, heterotrophic, aerobic, non-spore-forming and non-motile bacterial strain, designated LM5T, was isolated from activated sludge from a sequencing batch reactor for the treatment of effluents contaminated by malachite green. The taxonomy of strain LM5T was studied by phenotypic and phylogenetic methods. Strain LM5T formed orange colonies on R2A and YP plates. Cells were rods, 0.4–0.6 μm in diameter and 0.8–1.2 μm in length. Growth occurred at 10–35 °C (optimum, 20–25 °C), at pH 5.5–9.5 (optimum, pH 6.5–7.5) and in the presence of 0–2 % (w/v) NaCl (optimum, 0.5 %). Oxidase and catalase activities were present. Flexirubin-type pigments were present, but extracellular glycans were absent. MK-6 was the major respiratory quinone. The major fatty acids were iso-C15 : 0 (28.3 %) and iso-C17 : 1 ω9c (13.8 %). Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain LM5T was a member of the genus Flavobacterium with highest sequence similarity to Flavobacterium soli DS-6T (93.2 %) and Flavobacterium lindanitolerans IP-10T (92.9 %). Together with F. lindanitolerans IP-10T, strain LM5T formed a distinct lineage in the phylogenetic tree. The DNA G+C content was 52±0.6 mol% (HPLC), which is significantly higher than that of other species of the genus Flavobacterium (30–41 mol%). Based on phylogenetic and phenotypic evidence, strain LM5T is considered to represent a novel species of the genus Flavobacterium, for which the name Flavobacterium caeni sp. nov. is proposed; the type strain is LM5T (=CGMCC 1.7031T=NBRC 104239T).
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