The Composition of Diesel Fuel Influences the Structure of Microbiological Assemblages in Contaminated Fuel Storage Tanks

Microbiological contamination in diesel storage tanks is widespread and under-reported. The contaminating microorganisms can degrade components of the fuel, which contributes to fouling and corrosion. To better understand the connection between the microorganisms that are responsible for this contamination, the composition of affected fuels, and the resulting impact on fuel quality, we conducted a survey of 106 fuel tanks at 17 military bases across the continental United States. Fuel was sampled from each tank and the resident microbial communities were characterized using high throughput sequencing of small subunit ribosomal RNA gene libraries. Fatty acid methyl esters (FAME) and n-alkanes were characterized and quantified using GC-MS to determine their correlation with the presence of microbial taxa. Redundancy Analyses identified which microbial taxa were more prominent in contaminated fuels. Members of the fungal family Trichomaceae were found to be prominent in fuels containing more FAME. Members of the yeast family Debaryomycetaceae were found to be prominent in fuels containing more pentadecanoic and oleic acid methyl esters. These relationships between fungal taxa and fuel components were directly tested in growth experiments with representative isolates of the Trichocomaceae (Paecilomyces AF001) and Debaryomycetaceae (Wickerhamomyces SE3) families. Paecilomyces was capable of growth on linoleic acid methyl ester but unable to grow on pentadecanoic acid methyl ester, while Wickerhamomyces was able to grow on both substrates. Fuel composition may provide some insight into which microorganisms can proliferate but other factors like competition and symbiosis may also drive microbial proliferation, fouling, degradation, and corrosion in diesel fuels.