Xu Meixiang, Xiao Xiang, Wang Fengping
Key Laboratory of Marine Biogenetic Resources, Third Institute of Oceanography, State Oceanic Administration, Xiamen 361005, People's Republic of China.
Extremophiles. 2008 Mar;12(2):255-62. doi: 10.1007/s00792-007-0122-x. Epub 2007 Dec 18.
Two clones 9E7 and 21G8 in a metagenomic library of the east Pacific deep-sea sediment were found to contain alkane hydroxylase genes (alkB). The whole insert sequences of the two cosmid clones were determined. The insert sequences of 9E7 and 21G8 are 40 and 35 kb, respectively. Besides alkB, several alcohol/aldehyde dehydrogenase genes were also determined. A homolog of rubredoxin 2 of Pseudomonas putida was identified on 9E7 immediately downstream the alkB gene, but was lacking on 21G8. Unlike previous reports, the alkB genes on 9E7 and 21G8 have opposite transcription directions to those of linked alcohol/aldehyde dehydrogenase genes. Phylogenetic analysis put these two deep-sea AlkBs into a unique branch of integral membrane hydroxylases. The two alkB genes (9E7-alkB and 21G8-alkB) were cloned into pCom8 and introduced into two alkB expression host systems P. fluorescens KOB2 Delta 1 and P. putida GPo12 (pGEc47 Delta B). The transformed strains can grow on the n-alkanes from C5 to C16, indicating that both 9E7-AlkB and 21G8-AlkB have a wide substrate range. The data further indicate that the deep sea would be a rich resource for exploring novel alkane-degrading strains and genes.
在东太平洋深海沉积物的宏基因组文库中发现，两个克隆9E7和21G8含有烷烃羟化酶基因（alkB）。测定了这两个黏粒克隆的完整插入序列。9E7和21G8的插入序列分别为40 kb和35 kb。除alkB外，还测定了几个醇/醛脱氢酶基因。在9E7上alkB基因紧邻下游处鉴定出恶臭假单胞菌红素氧还蛋白2的一个同源物，但在21G8上没有。与之前的报道不同，9E7和21G8上的alkB基因与相连的醇/醛脱氢酶基因的转录方向相反。系统发育分析将这两种深海AlkB归入完整膜羟化酶的一个独特分支。将这两个alkB基因（9E7-alkB和21G8-alkB）克隆到pCom8中，并导入两个alkB表达宿主系统荧光假单胞菌KOB2 Delta 1和恶臭假单胞菌GPo12（pGEc47 Delta B）。转化菌株能够在C5至C16的正构烷烃上生长，这表明9E7-AlkB和21G8-AlkB都具有广泛的底物范围。这些数据进一步表明，深海将是探索新型烷烃降解菌株和基因的丰富资源。
