The rates of biodegradation of phthalate esters, under aerobic and anaerobic conditions, will be determined using waters and sediments from the Miami River and nearby marine regions. Fish, and other macroorganisms, will be analyzed for phthalate ester contents. Anaerobic bacteria (photosynthetic, sulfate-respiring, nitrate-respiring) with phthalate-esterase activity will be isolated. Cell-free preparations of these organisms, and of aerobic bacteria already isolated, will be examined for esterase specificity. The biochemical pathways for the anaerobic catabolism of o-phthalic and p-phthalic acids will be investigated with denitrifying bacterial cultures already obtained. o-Phthalic acid is first converted by cell suspensions, under anaerobic conditions, to benzoic acid. Studies will concentrate upon the initial stages of metabolism of the two phthalic acids by cell-free systems. Breakdown beyond benzoic acid will be examined with intact cells using o-chlorobenzoic acid as an inhibitor; intermediates which accumulate will allow elucidation of the catabolic route beyond benzoic acid. BIBLIOGRAPHIC REFERENCE: Taylor, B.F. 1975. Degradation of o-Phthalic Acid and Some of Its Esters by Marine Bacteria. Amer. Soc. Microbiol. Ann. Meet. Abstract N25, p. 188.