Dynamics and prevalence of specific hydrocarbonoclastic bacterial population with respect to nutrient treatment levels in crude oil sludge.

Abstract

The bacterial community composition in soil sediments changes with respect to nutrient concentrations and environmental conditions. Reports on the correlation between bacterial populations and inorganic nutrient concentrations in oily sediments are limited. The present time series study reports the prevalence of specific hydrocarbon-degrading bacterial communities in nutrient-treated oily sludge microcosms. The hydrocarbon degradation was maximum at 625µg nitrogen (N) and 62.5µg phosphorus (P)/g sludge sediment. The 16S rRNA gene-based DGGE analyses revealed noticeable changes in bacterial community composition with time and levels of nutrient treatment. BLASTn analysis of the 16S rRNA gene clone sequence showed the abundance of γ-Proteobacteria (44%), α-Proteobacteria (16%), β-Proteobacteria (10%), CFB (4%), and unidentified bacterial clones (26%). The catechol 1,2-dioxygenase (C12O) and catechol 2,3-dioxygenase (C23O) gene clones were affiliated to the genus Sphingomonas, highlighting the vital role of Sphingomonas in aromatic hydrocarbon degradation. The quantity of the 16S rRNA gene and the alkane hydroxylase (alkB) gene reached maximum levels in extended duration microcosms treated with 625µgN and 62.5µg P/g sludge sediment. In contrast, the C12O gene reached its highest abundance at a low N concentration.