To isolate and quantify diesel utilizing bacteria from Qua river sediments and ascertain their tolerance levels to varying concentrations of diesel was the primary aim of this study. Samples were collected and processed using standard microbiological techniques. Screening tests was then carried out using the vapour phase transfer method and incubated at room temperature (28±2⁰C). The highest diesel utilizing bacterial count was 9.7 x 10³CFU/g recorded for sample(3) while the least bacterial count was 6.0 x 10³CFU/g recorded for sample one(1). Pseudomonas sp., Micrococcus luteus and Bacillus sp. were the identified diesel utilizing bacterial isolates. Tests to determine the tolerance of these isolates to 1%, 3%, 5% and 7% diesel in Mineral salt broth proved by optical densities (OD_600nm) that Micrococcus luteus showed less growth (OD_600nm) to 1%(0.279), 3%(0.253) and 5%(0.154) diesel than Pseudomonas sp. at1%(0.685), 3%(0.483) and 5%(0.466) and Bacillus sp. at 1%(0.509), 3%(0.452) and 5%(0.390) but showed slightly higher growth (OD_600nm) at 7%(0.1) than Pseudomonas sp. (0.095) and Micrococcus luteus (0.093). ANOVA at 5% significance level proved that there is significant difference of diesel concentrations on growth (OD_600nm) of these isolates. These results highlight Qua River as a potential source for petroleum bioremediating bacteria.

Key words: diesel-utilizing bacteria, sediments, hydrocarbon degradation, bacterial identification, bioremediation