Department of Environmental Microbiology, Helmholtz Centre for Infection Research, Braunschweig, Germany.
Appl Environ Microbiol. 2013 Jul;79(14):4282-93. doi: 10.1128/AEM.00694-13. Epub 2013 May 3.
The marine hydrocarbonoclastic bacterium Alcanivorax borkumensis is able to degrade mixtures of n-alkanes as they occur in marine oil spills. However, investigations of growth behavior and physiology of these bacteria when cultivated with n-alkanes of different chain lengths (C6 to C30) as the substrates are still lacking. Growth rates increased with increasing alkane chain length up to a maximum between C12 and C19, with no evident difference between even- and odd-numbered chain lengths, before decreasing with chain lengths greater than C19. Surface hydrophobicity of alkane-grown cells, assessed by determination of the water contact angles, showed a similar pattern, with maximum values associated with growth rates on alkanes with chain lengths between C11 and C19 and significantly lower values for cells grown on pyruvate. A. borkumensis was found to incorporate and modify the fatty acid intermediates generated by the corresponding n-alkane degradation pathway. Cells grown on distinct n-alkanes proved that A. borkumensis is able to not only incorporate but also modify fatty acid intermediates derived from the alkane degradation pathway. Comparing cells grown on pyruvate with those cultivated on hexadecane in terms of their tolerance toward two groups of toxic organic compounds, chlorophenols and alkanols, representing intensely studied organic compounds, revealed similar tolerances toward chlorophenols, whereas the toxicities of different n-alkanols were significantly reduced when hexadecane was used as a carbon source. As one adaptive mechanism of A. borkumensis to these toxic organic solvents, the activity of cis-trans isomerization of unsaturated fatty acids was proven. These findings could be verified by a detailed transcriptomic comparison between cultures grown on hexadecane and pyruvate and including solvent stress caused by the addition of 1-octanol as the most toxic intermediate of n-alkane degradation.
海洋烃降解菌 Alcanivorax borkumensis 能够降解海洋溢油中存在的混合正构烷烃。然而，对于这些细菌在以不同链长（C6 到 C30）的正构烷烃作为底物进行培养时的生长行为和生理学的研究仍然缺乏。生长速率随烷烃链长的增加而增加，在 C12 和 C19 之间达到最大值，偶数和奇数链长之间没有明显差异，然后随着链长大于 C19 而减少。通过测定水接触角评估的烷烃生长细胞的表面疏水性呈现出相似的模式，最大值与 C11 和 C19 之间的烷烃生长速率相关，而与丙酮酸生长的细胞相比，值显著降低。发现 A. borkumensis 能够吸收和修饰相应正构烷烃降解途径产生的脂肪酸中间产物。用不同的正构烷烃培养的细胞证明，A. borkumensis 不仅能够吸收，还能够修饰来自烷烃降解途径的脂肪酸中间产物。将以丙酮酸生长的细胞与以十六烷生长的细胞在耐受两组毒性有机化合物（氯酚和烷醇）方面进行比较，这些化合物代表了经过深入研究的有机化合物，发现它们对氯酚的耐受性相似，而当十六烷作为碳源时，不同正烷醇的毒性显著降低。作为 A. borkumensis 对这些有毒有机溶剂的一种适应机制，证明了不饱和脂肪酸的顺反异构化活性。通过在十六烷和丙酮酸培养物之间进行详细的转录组比较，并包括添加 1-辛醇作为最毒的正构烷烃降解中间产物引起的溶剂应激，可以验证这些发现。
