Mucilaginibacter paludis gen. nov., sp. nov. and Mucilaginibacter gracilis sp. nov., pectin-, xylan- and laminarin-degrading members of the family Sphingobacteriaceae from acidic Sphagnum peat bog

Abstract

Two facultatively aerobic, heterotrophic bacteria capable of degrading pectin, xylan, laminarin and some other polysaccharides were obtained from the acidic Sphagnum peat bog Bakchar, in western Siberia, Russia, and were designated strains TPT18T and TPT56T. Cells of these isolates are Gram-negative, non-motile, long rods that are covered by large capsules. On ageing, they transform into spherical L-forms. Strains TPT18T and TPT56T are acido- and psychrotolerant organisms capable of growth at pH 4.2–8.2 (with an optimum at pH 6.0–6.5) and at 2–33 °C (with an optimum at 20 °C). The major fatty acids are iso-C15 : 0, anteiso-C15 : 0, iso-C17 : 0 3-OH and summed feature 3 (iso-C15 : 0 2-OH and/or C16 : 1 ω7c); the quinones are MK-7 and MK-6. Comparative 16S rRNA gene sequence analysis revealed that the novel strains share 97 % sequence similarity and belong to the family Sphingobacteriaceae; however, they are related only distantly to members of the genera Pedobacter (91.8–93.3 % similarity) and Sphingobacterium (89.6–91.2 % similarity). The DNA G+C content of strains TPT18T and TPT56T is 42.4 and 46.1 mol%, respectively. The low DNA–DNA hybridization value (42 %) and a number of phenotypic differences between strains TPT18T and TPT56T indicated that they represent two separate species. Since the two isolates are clearly distinct from all currently described members of the family Sphingobacteriaceae, we propose a novel genus, Mucilaginibacter gen. nov., containing two novel species, Mucilaginibacter gracilis sp. nov. and Mucilaginibacter paludis sp. nov. The type strains of Mucilaginibacter gracilis and Mucilaginibacter paludis are respectively TPT18T (=ATCC BAA-1391T =VKM B-2447T) and TPT56T (=ATCC BAA-1394T =VKM B-2446T).