Larkinella arboricola sp. nov., a new spiral-shaped bacterium of the phylum Bacteroidetes isolated from the microbial community of decomposing wood

An aerobic gram-negative bacterial strain Z-0532 with ring-shaped cells forming spirals in the course of growth was isolated from the humified solution produced by spruce wood decomposition. The new isolate was a chemoorganotrophic, mesophilic, moderately acidophilic organism with the temperature range of 6-32°C (optimum at 25-28°C) and pH range from 4.7 to 7.2 (optimum at pH 5.5-6.5). A broad range of substrates was used as carbon and energy sources, including sugars, some organic acids and polyalcohols, and soluble polymeric compounds (gelatin, esculin, starch, xylan, laminarin, dextrin, casein hydrolysate, and Tween-40). According to its physiological and biochemical characteristics, strain Z-0532 is a typical member of the trophic group of oligotrophic bacteria, which utilize the products of wood hydrolysis dissipated by xylotrophic microorganisms. The G+C base content of strain Z-0532 was 52.1 mol %. Sequencing of the 16S rRNA gene of the new isolate revealed 98% similarity to Larkinella insperata LMG 22510T, which is a recently described species of the family Spirosomaceae of the phylum Bacteroidetes. The level of DNA: DNA homology between this species and strain Z-0532 was only 40%. The differences in the phenotypic and genotypic characteristics suggested classification of the isolate obtained from decomposing wood as a new species of the genus Larkinella, Larkinella arboricola sp. nov., with the type strain Z-0532T (=VKM B-2528T = DSM 21851T).