Acidicapsa borealis gen. nov., sp. nov. and Acidicapsa ligni sp. nov., subdivision 1 Acidobacteria from Sphagnum peat and decaying wood

Abstract

Two strains of subdivision 1 Acidobacteria , a pink-pigmented bacterium KA1T and a colourless isolate WH120T, were obtained from acidic Sphagnum peat and wood under decay by the white-rot fungus Hyploma fasciculare, respectively. Cells of these isolates were Gram-negative-staining, non-motile, short rods, which were covered by large polysaccharide capsules and occurred singly, in pairs, or in short chains. Strains KA1T and WH120T were strictly aerobic mesophiles that grew between 10 and 33 °C, with an optimum at 22–28 °C. Both isolates developed under acidic conditions, but strain WH120T was more acidophilic (pH growth range 3.5–6.4; optimum, 4.0–4.5) than strain KA1T (pH growth range 3.5–7.3; optimum , 5.0–5.5). The preferred growth substrates were sugars. In addition, the wood-derived isolate WH120T grew on oxalate, lactate and xylan, while the peat-inhabiting acidobacterium strain KA1T utilized galacturonate, glucuronate and pectin. The major fatty acids were iso-C15 : 0 and iso-C17 : 1ω8c; the cells also contained significant amounts of 13,16-dimethyl octacosanedioic acid. The quinone was MK-8. The DNA G+C contents of strains KA1T and WH120T were 54.1 and 51.7 mol%, respectively. Strains KA1T and WH120T displayed 97.8 % 16S rRNA gene sequence similarity to each other. The closest recognized relatives were Acidobacterium capsulatum and Telmatobacter bradus (93.4–94.3 % 16S rRNA gene sequence similarity). These species differed from strains KA1T and WH120T by their ability to grow under anoxic conditions, the absence of capsules, presence of cell motility and differing fatty acid composition. Based on these differences, the two new isolates are proposed as representing a novel genus, Acidicapsa gen. nov., and two novel species. Acidicapsa borealis gen. nov., sp. nov. is the type species for the new genus with strain KA1T ( = DSM 23886T = LMG 25897T = VKM B-2678T) as the type strain. The name Acidicapsa ligni sp. nov. is proposed for strain WH120T ( = LMG 26244T = VKM B-2677T = NCCB 100371T).