title: Temperature-dependent expression of phzM and its regulatory genes lasI and ptsP in rhizosphere isolate Pseudomonas sp. strain M18.
abstract: Pseudomonas sp. strain M18, an effective biological control agent isolated from the melon rhizosphere, has a genetic background similar to that of the opportunistic human pathogen Pseudomonas aeruginosa PAO1. However, the predominant phenazine produced by strain M18 is phenazine-1-carboxylic acid (PCA) rather than pyocyanin (PYO); the quantitative ratio of PCA to PYO is 105 to 1 at 28 degrees C in strain M18, while the ratio is 1 to 2 at 37 degrees C in strain PAO1. We first provided evidence that the differential production of the two phenazines in strains M18 and PAO1 is related to the temperature-dependent and strain-specific expression patterns of phzM, a gene involved in the conversion of PCA to PYO. Transcriptional levels of phzM were measured by quantitative real-time PCR, and the activities of both transcriptional and translational phzM'-'lacZ fusions were determined in strains M18 and PAO1, respectively. Using lasI::Gm and ptsP::Gm inactivation M18 mutants, we further show that expression of the phzM gene is positively regulated by the quorum-sensing protein LasI and negatively regulated by the phosphoenolpyruvate phosphotransferase protein PtsP. Surprisingly, the lasI and ptsP regulatory genes were also expressed in a temperature-dependent and strain-specific manner. The differential production of the phenazines PCA and PYO by strains M18 and PAO1 may be a consequence of selective pressure imposed on P. aeruginosa PAO1 and its relative M18 in the two different niches over a long evolutionary process.
authors.affiliation: Key Laboratory of Microbial Metabolism, Ministry of Education, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China.
authors.forename: Jiaofang
authors.initials: J
authors.lastname: Huang
authors.forename: Yuquan
authors.initials: Y
authors.lastname: Xu
authors.forename: Hongyan
authors.initials: H
authors.lastname: Zhang
authors.forename: Yaqian
authors.initials: Y
authors.lastname: Li
authors.forename: Xianqing
authors.initials: X
authors.lastname: Huang
authors.forename: Bin
authors.initials: B
authors.lastname: Ren
authors.forename: Xuehong
authors.initials: X
authors.lastname: Zhang
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D002874:Chromosome Mapping; D019662:Cucurbitaceae / Q000382:microbiology; D017931:DNA Primers / Q000235:genetics; D004269:DNA, Bacterial / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D006801:Humans; D008780:Methyltransferases / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D010619:Phenazines / Q000378:metabolism; D014176:Protein Biosynthesis; D011549:Pseudomonas / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D011550:Pseudomonas aeruginosa / Q000235:genetics / Q000378:metabolism; D011710:Pyocyanine / Q000378:metabolism; D013045:Species Specificity; D013696:Temperature; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; D017931:DNA Primers; D004269:DNA, Bacterial; D010619:Phenazines; C037165:1-phenazinecarboxylic acid; D011710:Pyocyanine; D008780:Methyltransferases; C439052:PhzM protein, Pseudomonas aeruginosa