Asticcacaulis benevestitus sp nov., a psychrotolerant, dimorphic, prosthecate bacterium from tundra wetland soil

A Gram-negative, aerobic, heterotrophic, non-pigmented, dimorphic prosthecate bacterium was isolated from tundra wetland soil and designated strain Z-0023(T). Cells of this strain had a dimorphic life cycle and developed a non-adhesive stalk at a site not coincident with the centre of the cell pole, a characteristic typical of representatives of the genus Asticcacaulis. A highly distinctive feature of cells of strain Z-0023(T) was the presence of a conical, bell-shaped sheath when grown at low temperature. This prosthecate bacterium was a psych rotolerant, moderately acidophilic organism capable of growth between 4 and 28 degrees C (optimum 15-20 degrees C) and between PH 4-5 and 8-0 (optimum 5-6-6-0). The major phospholipid fatty acid was 18 : 1 omega 7C and the major phospholipids were phosphaticlylglycerols. The G +C content of the DNA was 60-4 mol%. On the basis of 16S rRNA gene sequence similarity, strain Z-0023(T) was most closely related to Asticcacaulis biprosthecium (98 % similarity), Asticcacaulis taihuensis (98 %) and Asticcacaulis excentricus (95 %). However, low levels of DNA-DNA relatedness to these organisms and a number of distinctive features of the tundra wetland isolate indicated that it represented a novel species of the genus Asticcacaulis, for which the name Asticcacaulis benevestitus sp. nov. is proposed. The type strain is Z-0023(T) (= DSM 16100(T) =ATCC BAA-896(T)).