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Updated: Jul 8, 2026

Culture of Small Colony Variant of Pseudomonas aeruginosa and Quantitation of its Alginate
Published on: February 22, 2020
QscR acts as an intermediate in gacA-dependent regulation of PCA biosynthesis in Pseudomonas sp. M-18
Yi Wang1, Xianqing Huang, Hongbo Hu
1Ministry of Education, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai, 200240, People's Republic of China.
Abstract:
The qscR gene, encoding a quorum sensing regulator, was cloned and the qscR-null mutant strain M-18Q derived from Pseudomonas sp. M-18 was constructed to study the effect of the qscR gene on biosynthesis of phenazine-1-carboxylic acid (PCA) and pyoluteorin (Plt) in strain M-18. Results showed that the PCA produced in the mutant increased four- to six-fold, while the synthesis of Plt was barely influenced in comparison with the wild type. The results were confirmed by complementation with the qscR gene in trans in strain M-18Q. The negative effect of the qscR gene on PCA production was further confirmed by analysis of beta-galactosidase activities from the translational phzA'-lacZ' fusion. Furthermore, by introducing a qscR-lacZ transcriptional fusion vector to strains M-18, M-18Q, and M-18G, a gacA inactivation mutant in strain M-18, respectively, it was found that beta-galactosidase activity in both strain M-18G and strain M-18Q was decreased to half that in the wild type. This suggested that QscR might be involved in autoinducing its own gene expression and act as an intermediate in GacA-dependent gene regulation as well. The result was further demonstrated by the overexpression of the gacA gene in strain M-18Q.
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