Characterization of microbial contamination in United States Air Force aviation fuel tanks

Abstract

Bacteria and fungi, isolated from United States Air Force (USAF) aviation fuel samples, were identified by gas chromatograph fatty acid methyl ester (GC-FAME) profiling and 16S or 18S rRNA gene sequencing. Thirty-six samples from 11 geographically separated USAF bases were collected. At each base, an above-ground storage tank, a refueling truck, and an aircraft wing tank were sampled at the lowest sample point, or sump, to investigate microbial diversity and dispersion within the fuel distribution chain. Twelve genera, including four Bacillus species and two Staphylococcus species, were isolated and identified. Bacillus licheniformis, the most prevalent organism isolated, was found at seven of the 11 bases. Of the organisms identified, Bacillus sp., Micrococcus luteus, Sphinogmonas sp., Staphylococcus sp., and the fungus Aureobasidium pullulans have previously been isolated from aviation fuel samples. The bacteria Pantoea ananatis, Arthrobacter sp., Alcaligenes sp., Kocuria rhizophilia, Leucobacter komagatae, Dietza sp., and the fungus Discophaerina fagi have not been previously reported in USAF aviation fuel. Only at two bases were the same organisms isolated from all three sample points in the fuel supply distribution chain. Isolation of previously undocumented organisms suggests either, changes in aviation fuel microbial community in response to changes in aviation fuel composition, additives and biocide use, or simply, improvements in isolation and identification techniques.

Culture-Independent Analysis of Bacterial Fuel Contamination Provides Insight into the Level of Concordance with the Standard Industry Practice of Aerobic Cultivation

“…In contrast, only a single Pseudomonas phylotype was observed across 15 fuel samples when analyzed by DGGE (Table 1), and Pseudomonas reads constituted only 1.1% of 16S rRNA gene V6 amplicons recovered from the 4 samples examined (Table 3). These results suggest that Pseudomonas species may not play as central a role in fuel system contamination as has often been assumed in the literature (39,41). Their overrepresentation in previous reports may be due to the robust, nonfastidious nature of isolates belonging to this genus, which grow quickly on industry standard TSA nutrient.…”

“…This depth of analysis and taxonomic specificity in terms of contaminant identification has not been previously applied to such environmental/industrial samples (25). In addition, despite cultivation-independent community analysis being applied to hydrocarbon-contaminated environments such as arctic ice (15) and mangrove sediments (51), there are few published reports of such molecular approaches being used directly on contaminated fuels (5,41).…”

“…Molecular methods with high discriminatory power and increased reproducibility now dominate the field of bacterial taxonomy, with 16S rRNA gene sequencing-based identification approaches being widely used in environmental and clinical settings (17,38,49). The use of this technology to assess contamination of hydrocarbon fuel systems has been limited, with only a few studies examining biofouling in molecular detail (5,41).…”

Microbiologically Influenced Corrosion in Aluminium Alloys 7075 and 2024

“…The bacteria were found in corrosion product of a drain valve from military aircraft, and it is closely related to Bacillus megaterium species [37]. B megaterium bacteria have been declared before, by other authors, as fuel tank microbial contaminant of the United States Air Force aviation [21]. The presence of this type of bacteria in fuel tanks and drain valves [23] could be caused by changes in refinery practices and chemical composition of fuels or possibly by the increased use of fuel additives [20].…”

“…In the past, jet fuel contaminants have been reported to include a diverse group of bacteria and fungi, with the most common contaminant being the fungus Hormoconis resinae [20]. However, Rauch et al [21] investigated microbial contamination in the United States Air Force (USAF) aviation fuel tanks. They found 12 genera, including four Bacillus species and two Staphylococcus species.…”