EFFECTS OF HEAVY METAL COMPONENTS ON HYDROCARBON DEGRADING BACTERIA AS ABIOTIC STRESS ON HYDROCARBON CONTAMINATED SITES

In our study 11 hydrocarbon degrading aerobic microbe strains were examined. These strains are originated from Hungarian hydrocarbon contaminated sites (eg. petrol stations, pipeline breakages and former oil distribution facilities, sites) and as members of a product (soil and groundwater inoculum) they are used for bioremediation purposes. In some cases the mentioned strains are used on hydrocarbon contaminated sites that have heavy metal pollution also (eg. complex contaminations of heavy industrial areas). High heavy metal concentrations are toxic (Takacs et al., 2003) and able to decrease the growth of aerobic bacteria (Algaida et al, 2007). Our work was focused on this abiotic stress. This abiotic effect was studied by in vitro, agar diffusion hole tests and this method was used to determine the effect of 10, 100, 1000 and 5000 mg/l concentration of the chosen heavy metals (zinc, lead, copper, nickel and chromium[VI]) on the inoculum strains. Some of these elements (Zn, Cu) are essential but the excess of them is toxic (Raja et al, 2008). From practical point of view it was very important to determine whether the members of the inoculum are able to grow and degrade in groundwater or soil that is contaminated not only with hydrocarbon but with heavy metals also. After assessing the results of our study, strains from the inoculum, those could be selected that are able to degrade hydrocarbon compounds on these kinds of complex contaminated sites. Notes about heavy metal tolerance of the degrading strains could be added to the biodegrading products as information for users, to assure them the possibility of choosing the appropriate site specific inoculum.