Abstract
An anaerobic, acid-tolerant bacterium, CK55(T), was isolated from an acidic forest bog. Cells of CK55(T) stained Gram-negative but did not have an outer membrane. Cells were spore-forming, motile rods with peritrichous flagella, formed chains or aggregates and were linked by connecting filaments that were composed of a core and outer sheath. Cellobiose, glucose, xylose, mannose, mannitol, sucrose and peptone supported growth. Arabinose, lactose, raffinose, H(2)/CO(2), CO/CO(2), vanillate, Casamino acids and various purines and pyrimidines did not support growth. Growth on carbohydrates yielded acetate, butyrate, lactate, formate and H(2) as end-products. Growth was observed at pH 4.0--9.0, with an optimum at pH 6.5, and at 10--30 degrees C, with an optimum at 20--25 degrees C. At 20 degrees C, doubling times were 4 and 6 h at pH 6.5 and 4.0, respectively. Hydrogenase activity in cell-free extracts was 12 U (mg protein)(-1). CK55(T) did not: (i) contain detectable levels of CO, formate, lactate dehydrogenases or cytochromes; (ii) carry out dissimilatory reduction of nitrate or sulfate; or (iii) produce methane. Thus, CK55(T) was characterized as a non-acetogenic, fermentative chemo-organotroph. The G+C content of CK55(T) was 28.0 mol%. CK55(T) was phylogenetically most closely related to Clostridium botulinum (types B, E and F), Clostridium acetobutylicum and other saccharolytic clostridia; the 16S rRNA gene sequence similarity values to the nearest relatives of CK55(T) were approximately 97%. Based on morphological, physiological and phylogenetic properties of CK55(T), it is proposed that CK55(T) be termed Clostridium uliginosum sp. nov. (=DSM 12992(T)=ATCC BAA-53(T)).