Community dynamics of a mixed-bacterial culture growing on petroleum hydrocarbons in batch culture

The effects of various hydrocarbon substrates. and a chemical surfactant ca pable of enhancing crude-oil biodegradation, on the community structure of a mixed-bacterial inoculum were examined in batch culture. Of 1000 TSA-cult urable isolates, 68.6% were identified at the genus level or better by phos pholipid fatty acid analysis over 7-day time course experiments. Cultures w ere exposed to 20 g/L Bow River crude oil with and without 0.625 g/L Igepal CO-630 (a nonylphenol ethoxylate surfactant), 5 g/L saturates, 5 g/L aroma tics, or 125 g/L refinery sludge. A group of six genera dominated the cultu res: Acinetobacter, Alcaligenes, Ochrobactrum, Pseudomonas/Flavimonas, Sten otrophomonas, and Yersinia. Species from four of the genera were shown to b e capable of hydrocarbon degradation, and counts of hydrocarbon degrading a nd total heterotrophic bacteria over time were nearly identical. Pseudomona s/Flavimonas and Stenotrophomonas normally dominated during the early porti ons of cultures, although the lag phase of Stenotrophomonas appears to have been increased by surfactant addition. Acinetobacter calcoaceticus was the most frequently isolated microorganism during exposure to the saturate fra ction of crude oil. Regardless of substrate, the culture medium supported a greater variety of organisms during the latter portions of cultures. Under standing the community structure and dynamics of mixed bacterial cultures i nvolved in treatment of heterogeneous waste substrates may assist in proces s development and optimization studies.