[Effects of insertional inactivation of gacS gene on two secondary metabolites in Psedomonas chlororaphis G-05].
Phenazine-1-carboxylic acid biosynthesized and secreted by Pseudomonas chlororaphis G-05 isolated from the rhizosphere of pepper in greenhouse (Huaian, China), contributes to its biological suppression of R. solani growth.


OBJECTIVE
Our aim is to elucidate its biocontrol function and regulation mechanism.


METHODS
We first identified the strain with biochemical method and homology comparison of 16S rDNA. A conservative DNA fragment of gacS gene was then obtained from the genomic DNA of the wild type strain G-05 by polymerase chain reaction (PCR). According to homologous recombination technology, a mutant G-05S was then created with insertional inactivation of gentamycin resistance cassette (aacC1).


RESULTS
In comparison with the wild type strain G-05, the gacS-deficient mutant G-05S produced trace amount of phenazine-1-carboxylic acid in King's B ( KMB ) or Pigment Production Medium( PPM) medium, respectively. However, it produced indole-3-acetic acid (IAA) in the same way as the wild type strain. When the gacS gene was introduced with the shuttle vector pME6032, the mutant G-05S produced the same phenazine-1-carboxylic acid as the wild type strain.


CONCLUSIONS
The regulation mediated by gacS gene on secondary metabolites is specific and differential in some biocontrol agents.
Ge
Yihe
Y
School of Life Sciences, Ludong University, Yantai 264000, China. geyihe@ldu.edu.cn
Chen
Lijuan
L
Wang
Lei
L
Su
Hongyan
H
Zhou
Jinfeng
J
Cheng
Xianhao
X
D001426:Bacterial Proteins / Q000037:antagonists & inhibitors*; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D007210:Indoleacetic Acids / Q000378:metabolism*; D016254:Mutagenesis, Insertional / Q000187:drug effects*; D010619:Phenazines / Q000494:pharmacology; D016133:Polymerase Chain Reaction; D011549:Pseudomonas / Q000187:drug effects* / Q000378:metabolism; D014157:Transcription Factors / Q000037:antagonists & inhibitors* / Q000172:deficiency
D001426:Bacterial Proteins; D007210:Indoleacetic Acids; D010619:Phenazines; D014157:Transcription Factors; C037165:1-phenazinecarboxylic acid; C030737:indoleacetic acid; C074165:lemA protein, bacterial