Project description:Pseudomonas chlororaphis strain 30-84 is an effective biological control agent against take-all disease of wheat. Phenazines, bacterial secondary metabolites produced by 30-84, are essential for 30-84 to inhibit fungal pathogens, form biofilms, and effectively colonize the rhizosphere. However, how the bacteria themselves respond to phenazines remains unknown. In this study, we conducted an RNA-seq analysis by comparing the wild type strain with a phenazine deficient mutant. RNA-seq analysis identified over 200 genes differentially regulated by phenazines. Consistent with previous findings in Pseudomonas aeruginosa PAO1, phenazines positively contribute to the expression of their own biosynthetic genes. Moreover, phenazine regulatory genes including the phzI/phzR quorum sensing system and the rpeB response regulatory were also expressed at high levels in the presence of phenazines. Besides phenazine biosynthesis and regulatory genes, genes involved in secondary metabolism, exopoysaccharide production and iron uptake as well as amino acid transport were identified as the major components under phenazine control, including many novel genes. We have also demonstrated that mutation of the primary siderophore gene pvdA resulted in up-regulation of phenazine genes when grown in iron-limiting media. These findings implicate phenazines as signaling molecules to regulate gene expression and hence alter metabolism in P. chlororaphis strain 30-84. A total of 4 samples were analyzed in AB medium + 2% casamino acids, Pseudomonas chlororaphis wild type strain (2 replicates); Pseudomonas chlororaphis ZN mutant (2 replicates).
Project description:The GacS/GacA two component regulatory system globally activates the production of secondary metabolites including phenazines in Pseudomonas chlororaphis 30-84. To better understand the regulatory role of the Gac system, we conducted RNA-seq analyses to determine the regulon of the response regulator GacA. Transcriptome analyses identified over 700 genes differentially regulated by GacA. Consistent with our previous findings, phenazine biosynthetic genes were significantly down-regulated in a gacA mutant. The expression levels of phenazine regulatory genes such as phzI, phzR, iopA, iopB, rpoS and pip were also decreased. Moreover, the expression of three none-coding RNAs (ncRNAs) including rsmX, rsmY and rsmZ was significantly decreased by gacA mutation consistent with the presence of GacA binding sites in their promoters. Our results also demonstrated that over-expression of rsmZ from a non-gac regulated promoter resulted in the restoration of AHL and phenazine production as well as the expression of other secondary metabolites in gac mutants. The role of RsmA and RsmE in phenazine production was also investigated. Over-expression of rsmE, but not rsmA, resulted in decreased AHL production and phenazine gene expression in P. chlororaphis. Consistently, a mutation in rsmE bypassed the requirement of GacA in phenazine gene expression. On the contrary, constitutive expression of the phzI/phzR quorum sensing system was not able to rescue phenazine production in the gacA mutant indicating the direct impact of Gac system on the transcript stability of phenazine biosynthetic genes. Together, these results indicate that the Gac system regulates phenazine production at multiple levels and exerts its positive effect on AHL and phenazine biosynthesis via RsmZ and RsmE. A model is proposed to illustrate the GacA regulon in P. chlororaphis 30-84. A total of 6 samples were analyzed in AB medium + 2% casamino acids, Pseudomonas chlororaphis wild type strain (3 replicates); Pseudomonas chlororaphis gacA mutant (3 replicates).
Project description:Pseudomonas chlororaphis strain 30-84 is an effective biological control agent against take-all disease of wheat. Phenazines, bacterial secondary metabolites produced by 30-84, are essential for 30-84 to inhibit fungal pathogens, form biofilms, and effectively colonize the rhizosphere. However, how the bacteria themselves respond to phenazines remains unknown. In this study, we conducted an RNA-seq analysis by comparing the wild type strain with a phenazine deficient mutant. RNA-seq analysis identified over 200 genes differentially regulated by phenazines. Consistent with previous findings in Pseudomonas aeruginosa PAO1, phenazines positively contribute to the expression of their own biosynthetic genes. Moreover, phenazine regulatory genes including the phzI/phzR quorum sensing system and the rpeB response regulatory were also expressed at high levels in the presence of phenazines. Besides phenazine biosynthesis and regulatory genes, genes involved in secondary metabolism, exopoysaccharide production and iron uptake as well as amino acid transport were identified as the major components under phenazine control, including many novel genes. We have also demonstrated that mutation of the primary siderophore gene pvdA resulted in up-regulation of phenazine genes when grown in iron-limiting media. These findings implicate phenazines as signaling molecules to regulate gene expression and hence alter metabolism in P. chlororaphis strain 30-84.
Project description:Pseudomonas chlororaphis strain 30-84 is an effective biological control agent against take-all disease of wheat. In this study, we conducted an RNA-seq analysis by comparing the wild type strain, PCA and O star with a phenazine deficient mutant. RNA-seq analysis identified over 800 genes differentially regulated by phenazines.
Project description:The GacS/GacA two component regulatory system globally activates the production of secondary metabolites including phenazines in Pseudomonas chlororaphis 30-84. To better understand the regulatory role of the Gac system, we conducted RNA-seq analyses to determine the regulon of the response regulator GacA. Transcriptome analyses identified over 700 genes differentially regulated by GacA. Consistent with our previous findings, phenazine biosynthetic genes were significantly down-regulated in a gacA mutant. The expression levels of phenazine regulatory genes such as phzI, phzR, iopA, iopB, rpoS and pip were also decreased. Moreover, the expression of three none-coding RNAs (ncRNAs) including rsmX, rsmY and rsmZ was significantly decreased by gacA mutation consistent with the presence of GacA binding sites in their promoters. Our results also demonstrated that over-expression of rsmZ from a non-gac regulated promoter resulted in the restoration of AHL and phenazine production as well as the expression of other secondary metabolites in gac mutants. The role of RsmA and RsmE in phenazine production was also investigated. Over-expression of rsmE, but not rsmA, resulted in decreased AHL production and phenazine gene expression in P. chlororaphis. Consistently, a mutation in rsmE bypassed the requirement of GacA in phenazine gene expression. On the contrary, constitutive expression of the phzI/phzR quorum sensing system was not able to rescue phenazine production in the gacA mutant indicating the direct impact of Gac system on the transcript stability of phenazine biosynthetic genes. Together, these results indicate that the Gac system regulates phenazine production at multiple levels and exerts its positive effect on AHL and phenazine biosynthesis via RsmZ and RsmE. A model is proposed to illustrate the GacA regulon in P. chlororaphis 30-84.
Project description:To better understand transcriptional changes in the SCV, RNA-seq analyses were conducted by comparing a SCV mutant to the wild-type. Transcriptomic profiling identified more than 1000 genes indicating a significant reprograming of gene expression in the SCV mutant. In accordance with observed phenotypes, genes involved in metabolism functions, motility and phenazine production were downregulated; whereas, oxidative stress and iron uptake genes were significantly upregulated. A total of 5 samples were analyzed in AB medium + 2% casamino acids, Pseudomonas chlororaphis wild type strain (3 replicates); Pseudomonas chlororaphis SCV mutant (2 replicates).
Project description:ErfA is a transcription factor of Pseudomonas aeruginosa. We here define the genome-wide binding sites of ErfA by DAP-seq in Pseudomonas aeruginosa PAO1 and IHMA87, Pseudomonas chlororaphis PA23, Pseudomonas protegens CHA0 and Pseudomonas putida KT2440.
Project description:The ability of certain Pseudomonas (P.) species to grow or persist in anoxic habitats by either denitrification, acetate fermentation or arginine fermentation has been described in several studies as a special property. Previously, we had isolated strains belonging to the species P. lundensis, P. weihenstephanensis and P. fragi from anoxic MAP minced beef and further proved their anaerobic growth in vitro on agar plates. This follow-up study investigated the anaerobic growth of two strains per respective species in situ on inoculated chicken breast fillet under 100% N2 modified atmosphere. We were able to prove anaerobic growth of all six strains on chicken breast fillet with cell division rates of 0.2-0.8 /day. Furthermore, we characterized the anaerobic metabolic lifestyle of these Pseudomonas strains by comparative proteomics, upon their cultivation in meat simulation media, which were constantly gassed with either air or 100% N2 atmospheres. From these proteomic predictions, and respective complementation by physiological experiments, we conclude that the Pseudomonas strains P. fragi, P. weihenstephanensis, P. lundensis exhibit a similar anaerobic lifestyle and employ arginine fermentation via the arginine deiminase (ADI) pathway to grow anaerobically also on MAP meats. Furthermore, glucose fermentation to ethanol via the ED-pathway is predicted to enable long term survival but no true growth, while respiratory growth with nitrate as alternative electron acceptor or glucose fermentation to acetate could be excluded due to absence of essential genes. The citric acid cycle is partially bypassed by the glyoxylate shunt, functioning as the gluconeogenetic route without production of NADH2 under carbon limiting conditions as e.g. in packaged meats. Triggered by an altered redox balance, we also detected upregulation of enzymes involved in protein folding as well as disulphide bonds isomerization under anoxic conditions as a counteracting mechanism to reduce protein misfolding. Hence, this study reveals the mechanisms enabling anaerobic grow and persistence of common meat-spoiling Pseudomonas species, and further complements the hitherto limited knowledge of the anaerobic lifestyle of Pseudomonas species in general.
Project description:Biofilms are ubiquitous in natural, medical, and engineering environments. While most antibiotics that primarily aim to inhibit cell growth may result in bacterial drug resistance, biofilm inhibitors do not affect cell growth and there is less chance of developing resistance. This work sought to identify novel, non-toxic and potent biofilm inhibitors from Streptomyces bacteria for reducing the biofilm formation of Pseudomonas aeruginosa PAO1. Out of 4300 Streptomyces strains, one species produced and secreted peptide(s) to inhibit P. aeruginosa biofilm formation by 93% without affecting the growth of planktonic cells. Global transcriptome analyses (DNA microarray) revealed that the supernatant of the Streptomyces 230 strain induced phenazine, pyoverdine, and pyochelin synthesis genes. Electron microscopy showed that the supernatant of Streptomyces 230 strain reduced the production of polymeric matrix in P. aeruginosa biofilm cells, while the Streptomyces species enhanced swarming motility of P. aeruginosa. Therefore, current study suggests that Streptomyces bacteria are an important resource of biofilm inhibitors as well as antibiotics.
Project description:Pseudomonas aeruginosa is a versatile opportunistic pathogen requiring iron for its survival and virulence within the host. The ability to switch to heme as an iron source provides an advantage in chronic infection. We have recently shown the extracellular heme metabolites biliverdin IX (BVIX) and/or BVIX positively regulate the heme dependent cell surface signaling cascade. We further investigated the role of BVIX and BVIX in cell signaling utilizing allelic strains lacking a functional HemO (hemOin), or one reengineered to produce BVIX (hemO). Compared to PAO1 both strains show a heme dependent growth defect, decreased swarming and twitching and less robust biofilm formation. Interestingly, the motility and biofilm defects were partially rescued on addition of exogenous BVIX and BVIX. Utilizing LC-MS/MS we performed a comparative proteomics and metabolomics analysis of PAO1 versus the allelic strains in shaking and static conditions. In shaking conditions, the hemO allelic strains showed a significant increase in proteins involved in quorum sensing (QS), phenazine production and chemotaxis.Metabolite profiling further revealed increased levels of PQS and phenazine metabolites. In static conditions we observed a significant repression of chemosensory pathways and Type IV pili (TFP) biogenesis proteins as well as several phosphodiesterases associated with biofilm dispersal. We propose BVIX metabolites function as signaling and chemotactic molecules integrating heme utilization as an iron source into the adaptation of P. aeruginosa from a planktonic to sessile lifestyle.