Water content, temperature and biocide effects on the growth kinetics of bacteria isolated from JP-8 aviation fuel storage tanks

Three bacterial strains isolated from JP-8 aviation fuel storage tanks were used to examine their ability to utilize the fuel as their sole source of carbon and energy. The isolates were Staphylococcus epidermidis, Agrobacterium tumefaciens and Ralstonia picketii. The purpose of this study was to determine the effect of temperature and water content on the growth kinetics of the bacterial isolates. Growth measurements were carried out by using light microscopy to enumerate bacterial cells. Growth phases of the bacterial cell cycle were determined under different experimental conditions and rate constants were calculated for the growth phase from the slopes of the graphical representations of ln(cells/ml) vs. time, assuming that bacterial growth follows a first order process. JP-8 fuel was found to support microbial growth, with increasing temperature and water content having a positive impact on the growth profiles of the bacterial strains. Biocidal activity of an isothiazolone biocide (Kathon FP 1.5) was also examined. The results indicate that the biocide can suppress the growth of S. epidermidis by 73%, A. tumefaciens by 77% and R. picketii by 81%, when used at the appropriate concentration. A mathematical model which correlates the number of cells and biocide concentration for each bacterial species was also developed.