Abstract
A gram-negative aliphatic hydrocarbon-degrading bacterium SJTD-1 isolated from oil-contaminated soil was identified as Pseudomonas aeruginosa by comparative analyses of the 16S rRNA sequence, phenotype, and physiological features. SJTD-1 could efficiently mineralize medium- and long-chain n-alkanes (C12-C30) as its sole carbon source within seven days, showing the most optimal growth on n-hexadecane, followed by n-octadecane, and n-eicosane. In 36 h, 500 mg/L of tetradecane, hexadecane, and octadecane were transformed completely; and 2 g/L n-hexadecane was degraded to undetectable levels within 72 h. Two putative alkane-degrading genes (gene 3623 and gene 4712) were characterized and our results indicated that their gene products were rate-limiting enzymes involved in the synergetic catabolism of C12–C16 alkanes. On the basis of bioinformatics and transcriptional analysis, two P450 monooxygenases, along with a putative AlmA-like oxygenase, were examined. Genetically defective mutants lacking the characteristic alkane hydroxylase failed to degrade n-octadecane, thereby suggesting a different catalytic mechanism for the microbial transformation of alkanes with chain lengths over C18.
Highlights
Oil pollution poses a severe threat to ecosystems, because of its refractory resistance to environmental degradation
Strain SJTD-1 isolated from the enrichment culture of oilcontaminated soil is a rod-shaped, gram-negative bacterium
SJTD-1 could not grow in the presence of ndecane or other shorter length n-alkanes, its growth was not inhibited by the short-chain n-alkanes like n-hexane
Summary
Oil pollution poses a severe threat to ecosystems, because of its refractory resistance to environmental degradation. In the past 30 years, several research groups around the world have tried to build robust biocatalysts for the efficient removal of contaminating oil residues. These attempts have not succeeded so far, the constant search for an effective biocatalyst has resulted in the discovery of a large number of microorganisms that could be used for bioremediation [2,3]. Several Pseudomonas strains are known to utilize aliphatic hydrocarbons as its sole carbon sources [13,14,15]. P. aeruginosa RR1 and P. fluorescens CHA0 degrade n-alkanes ranging from C12 to C34 [16,17]; and P. aeruginosa DQ8 can grow in the presence of n-tetrodecane, n-docosane, n-triacontane, and n-tetrocontane [8]
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