Inhibitive chemical cue of Pseudomonas pseudoalcaligene on biodegradation of anthracene in seawater medium

This study aims to reveal the self-inhibitive mechanism of an oil degrading bacteria, Pseudomonas pseudoalcaligene biodegradation of anthracene in seawater. Biodegradation of anthracene by the oil-degrading bacteria was analogue to the Monod equation and exhibited a typical bacterial growth pattern. Biodegradation of anthracene was retarded when the bacteria approached its stationary growth phase. The results indicated that the level of dissolved organic carbon and hydrogen ion in the seawater medium increased due to anthracene biodegradation. The organic compounds were believed to be secondary metabolites produced by the oil-degrading bacteria. These metabolites seem to inhibit activities of the oil degrading bacteria. The inhibitive effect was confirmed when the newly inoculated oil degrading bacteria failed to grow in the residue medium replenished with nutrients and new carbon source and incubated under optimal condition. It is interesting to note that, this replenished medium supported the growth of other non-oil degrading bacteria, Erythrobacter citreus. Presence of E. citreus in the medium utilized the inhibitive metabolites and thus resumed activities of the oil degrading bacteria for anthracene. Mixing the oil-degrading bacteria (P. pseudoalcaligenes) and non-oil degrading bacteria (E. citreus) improved biodegradation of anthracene in the seawater. The bacterial mixture improved anthracene degradation by 36% compared to the oil degrading bacteria alone.