Fall R R, Brown J L, Schaeffer T L
Appl Environ Microbiol. 1979 Oct;38(4):715-22. doi: 10.1128/aem.38.4.715-722.1979.
Experiments were carried out to construct pseudomonad strains capable of the biodegradation of certain recalcitrant branched hydrocarbons via a combination of alkane and citronellol degradative pathways. To promote the metabolism of the recalcitrant hydrocarbon 2,6-dimethyl-2-octene we transferred the OCT plasmid to Pseudomonas citronellolis, a pseudomonad containing the citronellol pathway. This extended the n-alkane substrate range of the organism, but did not permit utilization of the branched hydrocarbon even in the presence of a gratuitous inducer of the OCT plasmid. In a separate approach n-decane-utilizing (Dec+) mutants of P. citronellolis were selected and found to be constitutive for the expression of medium- to long-chain alkane oxidation. The Dec+ mutants were capable of degradation of 2,6-dimethyl-2-octene via the citronellol pathway as shown by (i) conversion of the hydrocarbon to citronellol, determined by gas-liquid chromatography-mass spectrometry, (ii) induction of geranyl-coenzyme A carboxylase, a key enzyme of the citronellol pathway, and (iii) demonstration of beta-decarboxymethylation of the hydrocarbon by whole cells. The Dec+ mutants had also acquired the capacity to metabolize other recalcitrant branched hydrocarbons such as 3,6-dimethyloctane and 2,6-dimethyldecane. These studies demonstrate how enzyme recruitment can provide a pathway for the biodegradation of otherwise recalcitrant branched hydrocarbons.
开展了实验，旨在通过烷烃和香茅醇降解途径的组合构建能够生物降解某些难降解支链烃的假单胞菌菌株。为促进难降解烃2,6-二甲基-2-辛烯的代谢，我们将OCT质粒转移至香茅假单胞菌，这是一种含有香茅醇途径的假单胞菌。这扩展了该生物体的正构烷烃底物范围，但即使在存在OCT质粒的 gratuitous 诱导剂的情况下，也不允许其利用支链烃。在另一种方法中，选择了利用正癸烷的（Dec+）香茅假单胞菌突变体，发现它们对于中长链烷烃氧化的表达是组成型的。如通过以下几点所示，Dec+突变体能够通过香茅醇途径降解2,6-二甲基-2-辛烯：（i）通过气液色谱-质谱法测定烃向香茅醇的转化；（ii）香茅醇途径的关键酶香叶酰辅酶A羧化酶的诱导；（iii）全细胞对烃的β-脱羧甲基化的证明。Dec+突变体还获得了代谢其他难降解支链烃的能力，如3,6-二甲基辛烷和2,6-二甲基癸烷。这些研究证明了酶的募集如何能够为原本难降解的支链烃的生物降解提供一条途径。
