FUNCTIONAL-ANALYSIS OF COMMUNITIES OF AEROBIC HETEROTROPHIC BACTERIA FROM HYDROCARBON-CONTAMINATED SITES

Microbial communities from soil and groundwater of oil-contaminated si tes (Beelitzhof in Berlin-Nikolassee and the former Pintsch site in Ha nau, bothin Germany) were characterized by description of the physiolo gical potential of arbitrary samples of 48 aerobic heterotrophic bacte rial isolates. It was demonstrated that the sum of metabolic abilities , presented as a percentage of substrate-degrading microorganisms in a sample, is both site specific and reproducible. The percentage of hyd rocarbon-degrading microorganisms in the communities was most strongly influenced by the diversity and amount of carbon supply (whereas afte r addition of mineral salts, total cell counts increased), For example , in groundwater of the waste oil-contaminated Pintsch site, only the accessible short-chain alkanes up to dodecane could be metabolized. Af ter dosing with hydrogen peroxide, long-chain alkane-degrading bacteri a were found in significant amounts among the predominant microorganis ms, which was apparently due to a solubilization effect that brought t he longer alkanes (and their degraders) into the groundwater. Because the addition of precultured organisms to a soil-composting windrow had no effect on the degradation pattern of its microbiota, the carbon so urces available probably determined whether allochthonous bacteria wou ld become indigenous. Although the physiological potentials of the ind ividual bacteria complemented each other and thus determined the disti nctive profile characteristic of the microbial community, the individu al members could differ in their metabolic abilities, as was shown by the distribution of positive test results in different samples, and th ey could also differ in their taxonomic status, Evidently, the taxonom ic status of the bacteria did not determine their activities: Strains of the same species showed different degradation abilities for hydroca rbon substrates. However, the taxonomic status of isolates seemed to b e highly dependent on the physicochemical factors of a site (soil stru cture, water capacity, etc.).