Zampolli Jessica, Collina Elena, Lasagni Marina, Di Gennaro Patrizia
Department of Biotechnology and Biosciences, University of Milano-Bicocca, Piazza della Scienza 2, Milano, 20126, Italy ; Department of Earth and Environmental Sciences, University of Milano-Bicocca, Milano, Italy.
Department of Earth and Environmental Sciences, University of Milano-Bicocca, Milano, Italy.
AMB Express. 2014 Sep 30;4:73. doi: 10.1186/s13568-014-0073-4. eCollection 2014.
Rhodococcus opacus R7 is a Gram-positive bacterium isolated from a polycyclic aromatic hydrocarbon contaminated soil for its versatile metabolism; indeed the strain is able to grow on naphthalene, o-xylene, and several long- and medium-chain n-alkanes. In this work we determined the degradation of n-alkanes in Rhodococcus opacus R7 in presence of n-dodecane (C12), n-hexadecane (C16), n-eicosane (C20), n-tetracosane (C24) and the metabolic pathway in presence of C12. The consumption rate of C12 was 88%, of C16 was 69%, of C20 was 51% and of C24 it was 78%. The decrement of the degradation rate seems to be correlated to the length of the aliphatic chain of these hydrocarbons. On the basis of the metabolic intermediates determined by the R7 growth on C12, our data indicated that R. opacus R7 metabolizes medium-chain n-alkanes by the primary alcohol formation. This represents a difference in comparison with other Rhodococcus strains, in which a mixture of the two alcohols was observed. By GC-MSD analysis we also identified the monocarboxylic acid, confirming the terminal oxidation. Moreover, the alkB gene cluster from R. opacus R7 was isolated and its involvement in the n-alkane degradation system was investigated by the cloning of this genomic region into a shuttle-vector E. coli-Rhodococcus to evaluate the alkane hydroxylase activity. Our results showed an increased biodegradation of C12 in the recombinant strain R. erythropolis AP (pTipQT1-alkR7) in comparison with the wild type strain R. erythropolis AP. These data supported the involvement of the alkB gene cluster in the n-alkane degradation in the R7 strain.
奥氏红球菌R7是一种革兰氏阳性细菌，从多环芳烃污染的土壤中分离出来，因其具有多种代谢功能；实际上，该菌株能够在萘、邻二甲苯以及几种长链和中链正构烷烃上生长。在这项工作中，我们测定了奥氏红球菌R7在存在正十二烷（C12）、正十六烷（C16）、正二十烷（C20）、正二十四烷（C24）的情况下对正构烷烃的降解情况以及在存在C12时的代谢途径。C12的消耗率为88%，C16为69%，C20为51%，C24为78%。降解率的下降似乎与这些烃类脂肪链的长度相关。根据R7在C12上生长所确定的代谢中间体，我们的数据表明奥氏红球菌R7通过生成伯醇来代谢中链正构烷烃。这与其他红球菌菌株不同，在其他菌株中观察到的是两种醇的混合物。通过气相色谱 - 质谱联用（GC - MSD）分析，我们还鉴定出了一元羧酸，证实了末端氧化。此外，分离出了奥氏红球菌R7的alkB基因簇，并通过将该基因组区域克隆到穿梭载体大肠杆菌 - 红球菌中来研究其在正构烷烃降解系统中的作用，以评估烷烃羟化酶活性。我们的结果表明，与野生型红平红球菌AP菌株相比，重组菌株红平红球菌AP（pTipQT1 - alkR7）中C12的生物降解有所增加。这些数据支持了alkB基因簇参与R7菌株中正构烷烃的降解。
