Chancey S T, Wood D W, Pierson L S
Department of Plant Pathology, University of Arizona, Tucson, Arizona 85721, USA.
Appl Environ Microbiol. 1999 Jun;65(6):2294-9. doi: 10.1128/AEM.65.6.2294-2299.1999.
Production of phenazine antibiotics by the biological control bacterium Pseudomonas aureofaciens 30-84 is regulated in part by the PhzI/PhzR N-acyl-homoserine lactone (AHL) response system (L. S. Pierson III, V. D. Keppenne, and D. W. Wood, J. Bacteriol. 176:3966-3974, 1994; D. W. Wood and L. S. Pierson III, Gene 168:49-53, 1996). Two mutants, 30-84W and 30-84.A2, were isolated and were found to be deficient in the production of phenazine, protease, hydrogen cyanide (HCN), and the AHL signal N-hexanoyl-homoserine lactone. These mutants were not complemented by phzI, phzR, or the phenazine biosynthetic genes (phzFABCD) (L. S. Pierson III, T. Gaffney, S. Lam, and F. Gong, FEMS Microbiol. Lett. 134:299-307, 1995). A 2.2-kb region of the 30-84 chromosome which fully restored production of all of these compounds in strain 30-84W was identified. Nucleotide sequence analysis of this region revealed a single open reading frame encoding a predicted 213-amino-acid protein which is very similar to the global response regulator GacA. Strain 30-84.A2 was not complemented by gacA or any cosmid from a genomic library of strain 30-84 but was complemented by gacS (formerly lemA) homologs from Pseudomonas fluorescens Pf-5 (N. Corbel and J. E. Loper, J. Bacteriol. 177:6230-6236, 1995) and Pseudomonas syringae pv. syringae B728a (E. M. Hrabek and D. K. Willis, J. Bacteriol. 174:3011-3020, 1992). Transcription of phzR was not altered in either mutant; however, phzI transcription was eliminated in strains 30-84W and 30-84.A2. These results indicated that the GacS/GacA two-component signal transduction system of P. aureofaciens 30-84 controls the production of AHL required for phenazine production by mediating the transcription of phzI. Addition of exogenous AHL did not complement either mutant for phenazine production, indicating that the GacS/GacA global regulatory system controls phenazine production at multiple levels. Our results reveal for the first time a mechanism by which a two-component regulatory system and an AHL-mediated regulatory system interact.
生防细菌金黄假单胞菌30 - 84产生吩嗪抗生素的过程部分受PhzI/PhzR N - 酰基高丝氨酸内酯（AHL）响应系统调控（L. S. Pierson III、V. D. Keppenne和D. W. Wood，《细菌学杂志》176:3966 - 3974，1994；D. W. Wood和L. S. Pierson III，《基因》168:49 - 53，1996）。分离出两个突变体30 - 84W和30 - 84.A2，发现它们在吩嗪、蛋白酶、氰化氢（HCN）以及AHL信号N - 己酰高丝氨酸内酯的产生方面存在缺陷。这些突变体不能被phzI、phzR或吩嗪生物合成基因（phzFABCD）互补（L. S. Pierson III、T. Gaffney、S. Lam和F. Gong，《FEMS微生物学快报》134:299 - 307，1995）。在30 - 84染色体上鉴定出一个2.2 kb的区域，该区域能完全恢复30 - 84W菌株中所有这些化合物的产生。对该区域的核苷酸序列分析揭示了一个单一的开放阅读框，编码一个预测的213个氨基酸的蛋白质，该蛋白质与全局响应调节因子GacA非常相似。30 - 84.A2菌株不能被gacA或来自30 - 84菌株基因组文库的任何粘粒互补，但能被来自荧光假单胞菌Pf - 5（N. Corbel和J. E. Loper，《细菌学杂志》177:6230 - 6236，1995）和丁香假单胞菌丁香致病变种B728a（E. M. Hrabek和D. K. Willis，《细菌学杂志》174:3011 - 3020，1992）的gacS（原lemA）同源物互补。在这两种突变体中，phzR的转录均未改变；然而，在30 - 84W和30 - 84.A2菌株中，phzI的转录被消除。这些结果表明，金黄假单胞菌30 - 84的GacS/GacA双组分信号转导系统通过介导phzI的转录来控制吩嗪产生所需的AHL的产生。添加外源AHL不能互补任何一种突变体的吩嗪产生，这表明GacS/GacA全局调节系统在多个水平上控制吩嗪的产生。我们的结果首次揭示了双组分调节系统和AHL介导的调节系统相互作用的机制。
