CHARACTERIZATION OF A NOVEL OBLIGATE ANAEROBE THAT FERMENTS AGAR

An agar-fermenting bacterium (strain 16AV) was isolated from the sedim ent of an abattoir effluent waste pond. The cells were curved rods, no n-motile, gramnegative, and did not form endospores. Old cultures prod uced spherical bodies that were not refractile and did not survive pas teurization at 80 degrees C for 5 min. Spherical cells were viable aft er at least 10 months storage at room temperature. The bacterium was m etabolically restricted and grew only on agar, agarose, galactose, and cellobiose. No inorganic electron accepters were reduced. Acetate and ethanol were produced as end products. Strain 16AV grew between 20 an d 37 degrees C, with optimum growth occurring at 28 degrees C. Growth occurred in medium containing NaCl from 0 to 15 g l(-1), with an optim um between 2.5 and 5 g l-(1). The DNA base composition was 39.5 mol% G +C. 16S rDNA sequence analysis showed that strain 16AV falls within th e radiation of members of the genus Clostridium and related taxa. This is the first description of an obligate anaerobe capable of degrading agar.