Effect of yeast extract on fluoranthene degradation and aromatic ring dioxygenase expressing bacterial community structure of a fluoranthene degrading bacterial consortium

Abstract

Fluoranthene (Fla) is a high molecular weight polycyclic aromatic hydrocarbon that exerts hazardous effects on living organisms. An efficient Fla degrading bacterial consortium LP was enriched from an oil contaminated soil sample, with and without yeast extract as a supplement. Objective of the present study was to see if there was any differential effect of yeast extract addition on Fla degradation potential and aromatic ring dioxygenase expressing bacteria (ARDB) of the enrichments. Primary enrichment of the soil sample was carried out in minimal salt medium (MSM) added with 500 mg l−1 Fla and 0.05% yeast extract (YMSM). Secondary, tertiary and subsequent enrichments were prepared in YMSM and MSM after every sixteen days of incubation. Fla was efficiently degraded by YMSM enriched culture than MSM enriched culture. However, when MSM enrichment was incubated longer instead of further subculturings, it also degraded Fla efficiently. All three enrichments exhibited growth of bacterial colonies on Fla sprayed minimal agar plates however only YMSM enrichment showed clear zone forming bacterial colonies. A positive effect was observed of yeast extract on ARDB population of LP consortium. To our limited knowledge this is first time that effect of yeast extract on ARDB population was studied.