Genetic analysis of xenocoumacin antibiotic production in the mutualistic bacterium Xenorhabdus nematophila
Genetic analysis of xenocoumacin antibiotic production in the mutualistic bacterium Xenorhabdus nematophila
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DOI：
10.1111/j.1365-2958.2009.06817.x
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发表时间：
2009-09-01
影响因子：
3.6
通讯作者：
Forst, Steven
中科院分区：
文献类型：
--
作者：
Park, Dongjin;Ciezki, Kristin;Forst, Steven
p> Xenocoumacin 1 （Xcn1）和Xenocoumacin 2 （Xcn2）是嗜线虫xenorhabduus nematophila产生的主要抗菌化合物。为了研究Xcn1和Xcn2在嗜线虫生命周期中的作用，鉴定了它们合成所需的14个基因簇（xcnA-N）。重叠RT-PCR分析鉴定出6个主要的xcn转录本。非核糖体肽合成酶基因xcnA和xcnK以及聚酮合成酶基因xcnF、xcnH和xcnL的失活消除了Xcn1的产生。在ompR菌株中，Xcn1表达量和xcnl表达量升高，Xcn2表达量和xcnMN表达量降低。在缺乏能向OmpR提供磷酸基的乙酰磷酸的菌株中，Xcn1的产量也增加了。综上所述，OmpR-phosphate负调控xcnA-L基因的表达，而正调控xcnMN的表达。HPLC-MS分析显示，Xcn1首先产生，随后转化为Xcn2。xcnM和xcnN的失活消除了Xcn1向Xcn2的转化，导致Xcn1产量升高。与野生型菌株相比，xcnM菌株的活力降低了20倍，这支持了Xcn1向Xcn2的转化提供了一种避免自毒性的机制。有趣的是，在长时间的培养过程中，ompR的失活增强了细胞的活力。
P>Xenocoumacin 1 (Xcn1) and xenocoumacin 2 (Xcn2) are the major antimicrobial compounds produced by Xenorhabdus nematophila. To study the role of Xcn1 and Xcn2 in the life cycle of X. nematophila the 14 gene cluster (xcnA-N) required for their synthesis was identified. Overlap RT-PCR analysis identified six major xcn transcripts. Individual inactivation of the non-ribosomal peptide synthetase genes, xcnA and xcnK, and polyketide synthetase genes, xcnF, xcnH and xcnL, eliminated Xcn1 production. Xcn1 levels and expression of xcnA-L were increased in an ompR strain while Xcn2 levels and xcnMN expression were reduced. Xcn1 production was also increased in a strain lacking acetyl-phosphate that can donate phosphate groups to OmpR. Together these findings suggest that OmpR-phosphate negatively regulates xcnA-L gene expression while positively regulating xcnMN expression. HPLC-MS analysis revealed that Xcn1 was produced first and was subsequently converted to Xcn2. Inactivation of xcnM and xcnN eliminated conversion of Xcn1 to Xcn2 resulting in elevated Xcn1 production. The viability of the xcnM strain was reduced 20-fold relative to the wild-type strain supporting the idea that conversion of Xcn1 to Xcn2 provides a mechanism to avoid self-toxicity. Interestingly, inactivation of ompR enhanced cell viability during prolonged culturing.