Characterisation of surfactant-expressing bacteria and their potential bioremediation properties from hydrocarbon-contaminated and uncontaminated soils

We are investigating characteristics associated with oil degradation amongst bacteria isolated from clean and hydrocarbon contaminated soils from Nigeria and the UK.Our focus has been to identify bacteria expressing surfactants following isolation on Pseudomonas selective (PSA-CFC) and non-selective nutrient media and investigate the nature of surfactants, heavy metal resistance and hydrocarbon-degrading enzymes expressed by the bacteria. Of five sites sampled, a total of 1460 colonies were tested using the drop collapse assay, and 110 were found to express surfactants reducing liquid surface tensions as assessed by quantitative tensiometry to between 24.7 and 26.7 mN.m-1 (Tukey-Kramer HSD, α=0.05). We undertook a range of growth and behaviour-based assays on 60 selected strain which, when investigated by Hierarchical cluster analysis (HCA) demonstrated that this collection showed considerable phenotypic diversity. Eight out of the 60 strains could grow at a high temperature (50 °C), 35 of the 60 strains utilized diesel as a sole carbon source, and most of the strains could tolerate high concentrations (up to 20 mM) of heavy metals. Identification by 16S rDNA sequencing revealed that some of the strains belong to Pseudomonas, Bacillus, and Stenotrophomonas genera. We found using bioinformatics analysis of eight-selected draft genome sequences (AntiSMASH and RAST) NRPS-like (probable surfactants), cytochrome P450, catechol-1,2/2,3-dioxygenase, lipase, and heavy metal resistance gene sequences. We intend to use the information provided in this research to select strains for potential applications in in-situor ex-situ bioremediation of hydrocarbon-contaminated soils.