Effects of ginkgolic acid(C15:1)on biofilm formation, pathogenic factor production and quorum sensing of Pseudomonas aeruginosa.

To complete the investigation of the bacterial inhibitory activity of ginkgolic acid (GA), the quorum sensing activity of GA was investigated to assess the potential of ginkgo biloba exocarp for the production of quorum sensing inhibitor. The effect of GA (C15:1) on the growth and secondary metabolism of p. aeruginosa PAO1 were tested. The results showed that GA (C15:1) had no effect on the growth of p. aeruginosa PAO1, and that GA (C15:1) was able to inhibit the formation of quorum sensing dependent virulence factors, but promoted the formation of biofilms. Finally, the above experimental results were verified by LasR-GFP, RhlR-GFP system and fluorescence quantitative PCR. These results suggested that GA (C15:1) was capable of modulating the quorum sensing system of p. aeruginosa PAO1 and possessed potential as an anti-virulence factor drug, but is not suitable for development as a broad-spectrum biofilm inhibitor.

Design, Synthesis and Biological Evaluation of Novel Anthraniloyl-AMP Mimics as PQS Biosynthesis Inhibitors Against Pseudomonas aeruginosa Resistance.

The Pseudomonas quinolone system (PQS) is one of the three major interconnected quorum sensing signaling systems in Pseudomonas aeruginosa. The virulence factors PQS and HHQ activate the transcription regulator PqsR (MvfR), which controls several activities in bacteria, including biofilm formation and upregulation of PQS biosynthesis. The enzyme anthraniloyl-CoA synthetase (PqsA) catalyzes the first and critical step in the biosynthesis of quinolones; therefore, it is an attractive target for the development of anti-virulence therapeutics against Pseudomonas resistance. Herein, we report the design and synthesis of novel triazole nucleoside-based anthraniloyl- adenosine monophosphate (AMP) mimics. These analogues had a major impact on the morphology of bacterial biofilms and caused significant reduction in bacterial aggregation and population density. However, the compounds showed only limited inhibition of PQS and did not exhibit any effect on pyocyanin production.

Comparison of transcriptomes of wild-type and isothiazolone-resistant Pseudomonas aeruginosa by using RNA-seq.

Isothiazolone biocides (such as Kathon) are widely used in a variety of industrial and domestic applications. However, the mechanisms through which bacteria develop resistance to these biocides are not completely clear. A better understanding of these mechanisms can contribute to optimal use of these biocides. In this study, transcription profiles of a Kathon-resistant strain of Pseudomonas aeruginosa (Pa-R) and the wild-type strain were determined using RNA sequencing (RNA-Seq) with the Illumina HiSeq 2000 platform. RNA-Seq generated 18,657,896 sequence reads aligned to 7093 genes. In all, 1550 differently expressed genes (DEGs, log2 ratio ≥1, false discovery rate (FDR) ≤0.001) were identified, of which 482 were up-regulated and 1068 were down-regulated. Most Kathon-induced genes were involved in metabolic and cellular processes. DEGs significantly enriched nitrogen metabolism and oxidative phosphorylation pathways. In addition, Pa-R showed cross-resistance to triclosan and ciprofloxacin and showed repressed pyocyanin production. These results may improve our understanding of the resistance mechanisms of P. aeruginosa against isothiazolones, and provide insight into the development of more efficient isothiazolones.