Degradation of Phthalic Acids by Denitrifying, Mixed Cultures of Bacteria

Abstract

Mixed cultures of bacteria, enriched from aquatic sediments, grew anaerobically on all three isomers of phthalic acid. Each culture grew anaerobically on only one isomer and also grew aerobically on the same isomer. Pure cultures were isolated from the phthalic acid (o-phthalic acid) and isophthalic acid (m-phthalic acid) enrichments that grew aerobically on phthalic and isophthalic acids. Cell suspension experiments indicated that protocatechuate is an intermediate of aerobic catabolism. Pure cultures which grew aerobically on terephthalic acid (p-phthalic acid) could not be isolated from the enrichments, and neither could pure cultures that grew anaerobically on any of the isomers. Cell suspension experiments suggested that separate pathways exist for the aerobic and anaerobic oxidation of phthalic acids. Each enrichment culture used only one phthalic acid isomer under anaerobic conditions, but all isomers were simultaneously adapted for the anaerobic catabolism of benzoate. Cells grown anaerobically on a phthalic acid immediately attacked the isomer under anaerobic conditions, whereas there was a lag before aerobic breakdown occurred, and, for phthalic and terephthalic acids, chloramphenicol stopped aerobic adaptation but had no effect on anaerobic catabolism. This work suggests that phthalic acids are biodegradable in anaerobic environments.