The growth of the Rhodococcus sp. on diesel fuel under the effect of heavy metals and different concentrations of zinc

Co-contamination of diesel fuel and heavy metals can be challenging for microbial remediation due to the complex composition of the fuel and the inhibitory effect of heavy metals. There is an urgent need to study this interaction to improve the pollutant removal efficiency in the Polar Regions. The growth of an Antarctic bacterium, Rhodococcus sp. was studied by comparing the growth at the logarithmic phase under the effect of selected heavy metals(Pb, Cr, As, Cd, Cu, Zn, Ni, Hg and Co). The selected heavy metals inhibited the growth of the Rhodococcus sp. on diesel fuel in an order from highest to lowest of: Hg > Zn > Cd > Cu > Co > Ni > As >Pb> Cr. Growth on diesel fuel co-contaminated with Hg and Zn were 2.95% and 5.71%,respectively compared to the no-metal control. A further experiment with various Zn concentrations was conducted. The specific growth rate of Rhodococcus sp. co-contaminated with different concentrations of Zn showed a correlation coefficient(r) of 0.916, and was modelled with an exponential decay model. Additional investigation is needed to determine the effect of low concentration of Zn on hydrocarbon degradation. It is important to understand the relationships between microbes, hydrocarbons and heavy metals, especially in the Polar Regions because this interaction might be promising in treating hydrocarbon-polluted sites containing heavy metals. The data and results also provide baseline tools of bioremediation processes at low temperatures and the knowledge of the ecological roles of Rhodococcus sp. in Antarctica.