Clostridium uliginosum sp nov., a novel acid-tolerant anaerobic bacterium with connecting filaments

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/CO2, CO/CO2, vanillate, Casamino acids and various purines and pyrimidines did not support growth. Growth on carbohydrates yielded acetate, butyrate, lactate, formate and H, as end-products. Growth was observed at pH 4.0-9.0, with an optimum at pH 6.5, and at 10-30 degreesC, with an optimum at 20-25 degreesC. At 20 degreesC, 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, CK55T was characterized as a non-acetogenic, fermentative chemo-organotroph. The G+C content of CK55T was 28.0 mol%. CK55(T) was phylogenetically most closely related to Clostridium botulinum (types B, E and 6), Clostridium acetobutylicum and other saccharolytic clostridia; the 16S rRNA gene sequence similarity values to the nearest relatives of CK55T were approximately 97%. Based on morphological, physiological and phylogenetic properties of CK55T, it is proposed that CK55T be termed Clostridium uliginosum sp. nov. (= DSM 12992(T) = ATCC BAA-53(T).