Mesophilic chitin-degrading anaerobes isolated from an estuarine environment

Abstract

Eight strains of obligately anaerobic, mesophilic, chitinolytic bacteria were isolated from the sediment of an estuarine environment. The isolates were rod-shaped, Gram-negative, and formed terminal spherical spores that swelled the sporangium. The major products from the fermentation of chitin were: acetate, ethanol, formate, CO 2, H 2 and ammonia. Growth of the isolates was possible at pH values ranging from 5.0–9.0. During the fermentation of chitin, N-acetylglucosamine accumulated in the culture fluids and was not metabolized. No organic compounds other than chitin and its oligomers could be demonstrated to support growth of the isolates. Hydrolysis of chitin proceeded at a relatively low rate and was incomplete. Approximately 65% of the initial amount of chitin was hydrolyzed during a period of 5–10 days. Supplementation of the medium with yeast extract, casamino acids or peptone did not enhance the rate of chitin hydrolysis, but reducing agents such as Na 2S 2O 4 and Ti (III)-NTA markedly stimulated the rate of chitin fermentation. The ecological implications of the high degree of substrate specialization are discussed.