No abstract

Pseudomonas aeruginosa can utilize hydrocarbons, but different strains have various degrees of adaptation despite their highly conserved genome. P. aeruginosa ATCC 33988 is highly adapted to hydrocarbons, while P. aeruginosa strain PAO1, a human pathogen, is less adapted and degrades jet fuel at a lower rate than does ATCC 33988. We investigated fuel-specific transcriptomic differences between these strains in order to ascertain the underlying mechanisms utilized by the adapted strain to proliferate in fuel. During growth in fuel, the genes related to alkane degradation, heat shock response, membrane proteins, efflux pumps, and several novel genes were upregulated in ATCC 33988. Overexpression of alk genes in PAO1 provided some improvement in growth, but it was not as robust as that of ATCC 33988, suggesting the role of other genes in adaptation. Expression of the function unknown gene PA5359 from ATCC 33988 in PAO1 increased the growth in fuel. Bioinformatic analysis revealed that PA5359 is a predicted lipoprotein with a conserved Yx(FWY)xxD motif, which is shared among bacterial adhesins. Overexpression of the putative resistance-nodulation-division (RND) efflux pump PA3521 to PA3523 increased the growth of the ATCC 33988 strain, suggesting a possible role in fuel tolerance. Interestingly, the PAO1 strain cannot utilize n-C 8 and n-C 10 . The expression of green fluorescent protein (GFP) under the control of alkB promoters confirmed that alk gene promoter polymorphism affects the expression of alk genes. Promoter fusion assays further confirmed that the regulation of alk genes was different in the two strains. Protein sequence analysis showed low amino acid differences for many of the upregulated genes, further supporting transcriptional control as the main mechanism for enhanced adaptation.IMPORTANCE These results support that specific signal transduction, gene regulation, and coordination of multiple biological responses are required to improve the survival, growth, and metabolism of fuel in adapted strains. This study provides new insight into the mechanistic differences between strains and helpful information that may be applied in the improvement of bacterial strains for resistance to biotic and abiotic factors encountered during bioremediation and industrial biotechnological processes.

Understanding the effect of conventional and alternative fuels on the marine bacterial community is crucial, as it pertains to the impact, biodegradation, and final fate of these fuels in the environment. Metagenomics analysis demonstrated that conventional and alternative fuels promoted the growth of Proteobacteria. Marinobacter and Desulfovibrio were predominant in seawater exposed to conventional jet propellant-5 (JP-5), while Hyphomonas and Rhodovulum were most abundant in seawater with hydroprocessed renewable jet fuel (HRJ) and conventional F-76 diesel, respectively. The phyla Bacteroidetes, Firmicutes, and Lentisphaerae were underrepresented in samples with fuel, and these phyla were largely comprised of unclassified bacteria. Culture-dependent tests isolated several of the same genera detected in high abundance by metagenomics DNA sequencing, including Marinobacter, Rhodovulum, and Halobacillus. Growth studies in fuel and gas chromatography analysis demonstrated that isolates grew in fuel and metabolized hydrocarbons efficiently. The hydrocarbon degradation profile of each bacterium was conserved from conventional to alternative fuels. The study indicated that bacteria must out-compete others to get established and proliferate. Competition between hydrocarbon degraders was an important factor affecting the bioremediation process. This study provides insights into the growth characteristics of hydrocarbon-degrading bacteria and the effects of fuel on marine bacterial communities.

Rhodovulum sp. strain NI22 is a hydrocarbon-degrading member of the genus Rhodovulum. The draft genome of Rhodovulum sp. NI22 is 3.8 Mb in size, with 3,756 coding sequences and 64.4% G+C content. The catechol and gentisate pathways for naphthalene degradation are predicted to be present in Rhodovulum sp. NI22.

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Achromobacter spanius strain 6 is a Gram-negative soil bacterium isolated from a hydrocarbon-degrading microcosm. The draft genome sequence of A. spanius strain 6 is 6.57 Mb with a G+C content of 64.7% and 5,855 protein coding genes.

No abstract