Clostridium carboxidivorans sp. nov., a solvent-producing clostridium isolated from an agricultural settling lagoon, and reclassification of the acetogen Clostridium scatologenes strain SL1 as Clostridium drakei sp. nov.

Abstract

A novel solvent-producing, anaerobic clostridium, strain P7T, was isolated from sediment from an agricultural settling lagoon after enrichment with CO as the substrate. The metabolism of this Gram-positive, motile, spore-forming rod was primarily acetogenic. Acetate, ethanol, butyrate and butanol were the end-products of metabolism. Strain P7T grew on CO, H2/CO2, glucose, galactose, fructose, xylose, mannose, cellobiose, trehalose, cellulose, starch, pectin, citrate, glycerol, ethanol, propanol, 2-propanol, butanol, glutamate, aspartate, alanine, histidine, asparagine, serine, betaine, choline and syringate as sole substrates. Growth was not supported by methanol, formate, d-arabinose, fucose, lactose, melibiose, amygdalin, gluconate, lactate, malate, arginine, glutamine or vanillate. Nitrate reduction, production of indole, gelatin hydrolysis and aesculin hydrolysis were not observed. Analysis of the 16S rRNA gene sequence of the isolate showed that it was closely related to Clostridium scatologenes ATCC 25775T (99·7 % sequence similarity) and clostridial strain SL1T (99·8 % sequence similarity). Strain SL1 had been classified as a strain of C. scatologenes. However, DNA–DNA reassociation analysis showed that both strain P7T and strain SL1 represented novel clostridial species. It is proposed that strain P7T (=ATCC BAA-624T=DSM 15243T) be classified as the type strain of Clostridium carboxidivorans sp. nov. and that strain SL1T (=ATCC BAA-623T=DSM 12750T) be reclassified as the type strain of Clostridium drakei sp. nov.