Bioactive Compounds from P. pertomentellum That Regulate QS, Biofilm Formation and Virulence Factor Production of P. aeruginosa
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SUBMITTER: Hernandez-Moreno L
PROVIDER: S-EPMC10488431 | biostudies-literature | 2023 Aug
REPOSITORIES: biostudies-literature
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Project description:Cyclic di-GMP (c-di-GMP) is a ubiquitous bacterial second messenger molecule that is an important virulence regulator in the plant pathogen Erwinia amylovora Intracellular levels of c-di-GMP are modulated by diguanylate cyclase (DGC) enzymes that synthesize c-di-GMP and by phosphodiesterase (PDE) enzymes that degrade c-di-GMP. The regulatory role of the PDE enzymes in E. amylovora has not been determined. Using a combination of single, double, and triple deletion mutants, we determined the effects of each of the four putative PDE-encoding genes (pdeA, pdeB, pdeC, and edcA) in E. amylovora on cellular processes related to virulence. Our results indicate that pdeA and pdeC are the two phosphodiesterases most active in virulence regulation in E. amylovora Ea1189. The deletion of pdeC resulted in a measurably significant increase in the intracellular pool of c-di-GMP, and the highest intracellular concentrations of c-di-GMP were observed in the Ea1189 ΔpdeAC and Ea1189 ΔpdeABC mutants. The regulation of virulence traits due to the deletion of the pde genes showed two patterns. A stronger regulatory effect was observed on amylovoran production and biofilm formation, where both Ea1189 ΔpdeA and Ea1189 ΔpdeC mutants exhibited significant increases in these two phenotypes in vitro In contrast, the deletion of two or more pde genes was required to affect motility and virulence phenotypes. Our results indicate a functional redundancy among the pde genes in E. amylovora for certain traits and indicate that the intracellular degradation of c-di-GMP is mainly regulated by pdeA and pdeC, but they also suggest a role for pdeB in regulating motility and virulence.IMPORTANCE Precise control of the expression of virulence genes is essential for successful infection of apple hosts by the fire blight pathogen, Erwinia amylovora The presence and buildup of a signaling molecule called cyclic di-GMP enables the expression and function of some virulence determinants in E. amylovora, such as amylovoran production and biofilm formation. However, other determinants, such as those for motility and the type III secretion system, are expressed and functional when cyclic di-GMP is absent. Here, we report studies of enzymes called phosphodiesterases, which function in the degradation of cyclic di-GMP. We show the importance of these enzymes in virulence gene regulation and the ability of E. amylovora to cause plant disease.
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Project description:Pseudomonas aeruginosa infections are attributed to its ability to form biofilms and are difficult to eliminate with antibiotic treatment. Biofilm formation is regulated by quorum sensing (QS), an intracellular bacterial communication mechanism that allows the activation of numerous virulence factors and secondary metabolites. Targeting the QS pathway is a potential approach that prevents QS-controlled phenotypes and biofilm formation. For the first time, the current work has identified antiquorum sensing activity in the partially purified four fractions from the hot ethyl acetate extract of Cassia fistula fruit pods. Of the four fractions, only fraction-1 gave decreased AHL activity; the phytoconstituents in this fraction were identified as rhein, 3-aminodibenzofuran, 5-(hydroxymethyl)-2-(dimethoxymethyl)furan, and dihydrorhodamine. Fraction-1 (1 mg ml-1) and rhein (0.15 mg ml-1) showed 63% and 42.7% reduction in short-chain AHL production, respectively, without hindering the bacterial growth. Fraction-1 inhibited QS-mediated extracellular virulence factors viz. protease, elastase, pyocyanin, and rhamnolipid (p < 0.05). Quantitative analysis of biofilm formation showed 77% & 62.4% reduction by fraction-1 (1 mg ml-1) and rhein (0.15 mg ml-1) respectively. Confocal laser microscopy (CLMS) & scanning electron microscopy (SEM) confirmed the reduction of biofilm formation in Pseudomonas aeruginosa upon treatment with fraction-1 and rhein. Moreover, the in vivo study displayed that fraction-1 and rhein (standard) significantly enhanced the survival of Caenorhabditis elegans by suppressing the potency of virulence factors of Pseudomonas aeruginosa. Quantitative real-time polymerase chain reaction results demonstrated the down-regulation of QS-related genes, lasI, lasR, rhlI, and rhlR. In addition, in silico analysis divulged that a component identified by GC-MS displayed a strong affinity towards LasI and LasR. These findings suggest that potent phytochemicals from fraction-1, including rhein, could serve as novel phytotherapeutics in controlling emerging infections of antibiotic-resistant bacterial pathogens like Pseudomonas aeruginosa.
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