CALORAMATOR PROTEOCLASTICUS SP-NOV, A NEW MODERATELY THERMOPHILIC ANAEROBIC PROTEOLYTIC BACTERIUM

A new moderately thermophilic proteolytic anaerobe, strain U-T, was is olated from mesophilic granular methanogenic sludge. The cells were sp ore-forming, motile rods that were 0.4 mu m wide and 2.4 to 4 mu m lon g and stained gram negative. Electron micrographs of thin sections rev ealed the presence of an atypical gram-positive cell wall. Optimum gro wth occurred at 55 degrees C and at pH values between 7.0 and 7.5, wit h a doubling time of 30 min. The DNA base ratio of guanine plus cytosi ne was 31 mol%. The bacterium fermented proteins mainly to acetate, hy drogen, formate, and branched-chain fatty acids. Several amino acids, including glutamate, aspartate, arginine, histidine, threonine, methio nine, and branched-chain amino acids, were also utilized. Glutamate wa s degraded to acetate, formate, hydrogen, and alanine. In addition, th e strain degraded carbohydrates, including glucose, fructose, mannose, cellobiose, and starch, to acetate, ethanol, formate, lactate, and hy drogen. The results of a 16S rRNA sequence analysis phylogenetically p laced strain U-T in the low-guanine-plus cytosine-content subgroup of the gram-positive phylum. We propose to classify the described strain in the genus Caloramator as a new species, Caloramator proteoclasticus . The type strain of C. proteoclasticus, strain U, has been deposited in the Deutsche Sammlung von Mikroorganismen as strain DSM 10124.