The naphthalene catabolic (nag) genes of Polaromonas naphthalenivorans CJ2:: Evolutionary implications for two gene clusters and novel regulatory control
The naphthalene catabolic (nag) genes of Polaromonas naphthalenivorans CJ2:: Evolutionary implications for two gene clusters and novel regulatory control
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DOI：
10.1128/aem.72.2.1086-1095.2006
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发表时间：
2006-02-01
影响因子：
4.4
通讯作者：
Madsen, EL
中科院分区：
文献类型：
--
作者：
Jeon, CO;Park, M;Madsen, EL
在煤焦油废物污染场地（c - o），发现萘酚单胞菌CJ2负责萘的原位降解。Jeon et al., Proc. Natl。学会科学。美国100:13591-13596,2003)，能够在矿物盐琼脂培养基上生长，萘作为唯一的碳源。从484 bp的nagac样区域开始，我们使用基因组行走策略对编码整个萘降解途径和其他侧翼区域的基因进行测序。我们发现，在P. naphthalenivorans CJ2中，萘分解代谢基因分为一个大基因簇和一个小基因簇，它们之间的距离未知。大基因簇（nagRAaGHAbAcAdBFCQEDJI ORFtnpA）由lysr型调节因子（nagR）结合。小簇（nagR20RF21”KL）由marr型调节器（nagR2）限定。P. naphthalenivorans CJ2的分解代谢基因与Ralstonia U2的许多基因同源，后者通过gentisate途径将萘转化为中心代谢物。然而，在Ralstonia U2中出现的三个开放阅读框架（nagY、nagM和nagN）没有出现。P. naphthalenivorans携带两个gentisate dioxygenase （nagI）拷贝，DNA序列同源性77.4%，与Ralstonia sp.菌株U2同源性82%。利用反转录PCR技术对其操纵子进行分析，发现每个簇都受各自的启动子独立控制。插入失活和lacZ报告基因试验表明，nagR2是一个负调控因子，并且小簇的表达不受萘、水杨酸盐或龙胆酸盐的诱导。两个与偶氮弧菌相关的转座酶与大簇的关联以及一个与偶氮弧菌相关的水杨酸5-羟化酶基因（ORF2）与小簇的关联表明，移动遗传元件可能参与了P. naphthalenivorans中分解代谢和调节基因的新排列。
Polaromonas naphthalenivorans CJ2, found to be responsible for the degradation of naphthalene in situ at a coal tar waste-contaminated site (C.-O. Jeon et al., Proc. Natl. Acad. Sci. USA 100:13591-13596, 2003), is able to grow on mineral salts agar media with naphthalene as the sole carbon source. Beginning from a 484-bp nagAc-like region, we used a genome walking strategy to sequence genes encoding the entire naphthalene degradation pathway and additional flanking regions. We found that the naphthalene catabolic genes in P. naphthalenivorans CJ2 were divided into one large and one small gene cluster, separated by an unknown distance. The large gene cluster (nagRAaGHAbAcAdBFCQEDJI ORFtnpA) is bounded by a LysR-type regulator (nagR). The small cluster (nagR20RF21"KL) is bounded by a MarR-type regulator (nagR2). The catabolic genes of P. naphthalenivorans CJ2 were homologous to many of those of Ralstonia U2, which uses the gentisate pathway to convert naphthalene to central metabolites. However, three open reading frames (nagY, nagM, and nagN), present in Ralstonia U2, were absent. Also, P. naphthalenivorans carries two copies of gentisate dioxygenase (nagI) with 77.4% DNA sequence identity to one another and 82% amino acid identity to their homologue in Ralstonia sp. strain U2. Investigation of the operons using reverse transcription PCR showed that each cluster was controlled independently by its respective promoter. Insertional inactivation and lacZ reporter assays showed that nagR2 is a negative regulator and that expression of the small cluster is not induced by naphthalene, salicylate, or gentisate. Association of two putative Azoarcus-related transposases with the large cluster and one Azoarcus-related putative salicylate 5-hydroxylase gene (ORF2) in the small cluster suggests that mobile genetic elements were likely involved in creating the novel arrangement of catabolic and regulatory genes in P. naphthalenivorans.