Caloramator coolhaasii sp nov., a glutamate-degrading, moderately thermophilic anaerobe

An obligately anaerobic, moderately thermophilic, glutamate-degrading bacterium (strain z(T)) was isolated from an enrichment culture obtained from anaerobic thermophilic granular sludge. The cells were rod-shaped to INTRODUCTION filamentous and showed no motility or spore formation. The cell wall had a Gram-positive structure, which was revealed by electron microscopy. Optimum growth of the strain was observed under neutrophilic conditions at 50-55 degrees C. The doubling time of strain Z(T) grown in rich medium was approximately 1 h at optimal pH and temperature. Strain Z(T) was able to grow on a variety of organic compounds. Most carbon sources were converted to acetate, CO2, H-2, and traces of propionate and lactate. Strain Z(T) oxidized glutamate to acetate, CO2 NH4+, traces of propionate and H-2. The doubling time on this substrate was 1.6 d. The strain fermented glutamate syntrophically in co-culture with Methanobacterium thermoautotrophicum Z-245(T) to the same products, but the co-culture had a fourfold higher growth rate. 16S rDNA sequence analysis revealed a relationship with Thermobrachium celere, Caloramator indicus and Caloramator proteoclasticus. The G+C content was 31.7 mol%. Based on its morphological, phylogenetic and physiological characteristics, it is proposed that strain Z(T) should be classified in the genus Caloramator as a new species, Caloramator coolhaasii.