Project description:Pseudomonas putida S12 is an inherently solvent-tolerant strain and constitutes a promising platform for biotechnology applications in whole-cell biocatalysis of aromatic compounds. The genome of P. putida S12 consists of a 5.8 Mbp chromosome and a 580 kbp megaplasmid pTTS12. pTTS12 encodes several genes which enable the tolerance to various stress conditions, including the main solvent efflux pump SrpABC. Removal (curing) of megaplasmid pTTS12 and subsequent loss of solvent efflux pump SrpABC caused a significant reduction in solvent tolerance of the resulting strain. In this study, we succeeded in restoring solvent tolerance in the megaplasmid-cured P. putida S12 using adaptive laboratory evolution (ALE) and molecular analysis to investigate the intrinsic solvent tolerance of P. putida S12. RNA-seq was performed to study the global transcriptomic response of the solvent-adapted plasmid-cured P. putida S12 in the presence of toluene. This analysis revealed the downregulation of ATP synthase, flagella and other RND efflux pumps, which indicates the importance of maintaining proton motive force during solvent stress.
Project description:Pseudomonas putida S12 is exceptionally tolerant to various organic solvents. To obtain further insight in this bacteriumM-bM-^@M-^Ys primary defence mechanisms towards these potentially harmful substances, we studied its genome wide transcriptional response to sudden addition of toluene. Global gene expression profiles were monitored for 30 minutes after toluene addition. During toluene exposure, high oxygen-affinity cytochrome c oxidase is specifically expressed to provide for an adequate proton gradient supporting solvent efflux mechanisms. Concomitantly, the glyoxylate bypass route was up-regulated, to repair an apparent toluene stress-induced redox imbalance. A knock-out mutant of trgI, a recently identified toluene-repressed gene, was investigated in order to identify TrgI function. Remarkably, upon addition of toluene the number of differentially expressed genes initially was much lower in the trgI-mutant than in the wild-type strain. This suggested that after deletion of trgI cells were better prepared for sudden organic solvent stress. Before, as well as after, addition of toluene many genes of highly diverse functions were differentially expressed in trgI-mutant cells as compared to wild-type cells. This led to the hypothesis that TrgI may not only be involved in the modulation of solvent-elicited responses but in addition may affect basal expression levels of large groups of genes. Differential gene expression after a sudden addition of 5 mM toluene was analysed in early exponential phase cultures (optical density at 600 nm of 0.5-0.6) of P. putida strains S12 (wild-type) and S12M-NM-^TtrgI. Samples were drawn immediately before (t=0) and at set intervals (1, 2, 5, 10 and 30 minutes) after toluene exposure. Duplicat samples were drawn. This resulted in 12 samples per strain, 24 in total.
Project description:KaiC is the central cog of the circadian clock in Cyanobacteria. Close homologs of this protein are widespread among bacteria not known to have a circadian physiology. The function, interaction network, and mechanism of action of these KaiC homologs are still largely unknown. Here, we focus on KaiC homologs found in environmental Pseudomonas species. We characterize experimentally the only KaiC homolog present in Pseudomonas putida KT2440 and Pseudomonas protegens CHA0. Through phenotypic assays and transcriptomics, we show that KaiC is involved in osmotic and oxidative stress resistance in P. putida and in biofilm production in both P. putida and P. protegens.
Project description:Pseudomonas putida S12 is exceptionally tolerant to various organic solvents. To obtain further insight in this bacterium’s primary defence mechanisms towards these potentially harmful substances, we studied its genome wide transcriptional response to sudden addition of toluene. Global gene expression profiles were monitored for 30 minutes after toluene addition. During toluene exposure, high oxygen-affinity cytochrome c oxidase is specifically expressed to provide for an adequate proton gradient supporting solvent efflux mechanisms. Concomitantly, the glyoxylate bypass route was up-regulated, to repair an apparent toluene stress-induced redox imbalance. A knock-out mutant of trgI, a recently identified toluene-repressed gene, was investigated in order to identify TrgI function. Remarkably, upon addition of toluene the number of differentially expressed genes initially was much lower in the trgI-mutant than in the wild-type strain. This suggested that after deletion of trgI cells were better prepared for sudden organic solvent stress. Before, as well as after, addition of toluene many genes of highly diverse functions were differentially expressed in trgI-mutant cells as compared to wild-type cells. This led to the hypothesis that TrgI may not only be involved in the modulation of solvent-elicited responses but in addition may affect basal expression levels of large groups of genes.