Metabolomics,Unknown,Transcriptomics,Genomics,Proteomics

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Cellular Response of the bacterium Cupriavidus metallidurans CH34 to Strontium: bio-precipitation as strontium carbonate.

ABSTRACT: The physiological and transcriptomic response of the metal resistant bacterium Cupriavidus metallidurans strain CH34 in response to stable (non-radioactive) strontium ions (Sr) was investigated. C. metallidurans CH34 could survive and proliferate in the presence of relatively high concentrations of SrCl2 (D10 is 70mM, MIC is 120 mM). Precipitation of Sr as strontium carbonate was observed in the culture during aerobic growth of CH34 in the presence of 60 mM SrCl2. To identify the cellular mechanisms involved in the bioprecipitation process, gene expression in the cells was analyzed after short-time (30 min) exposure to low (5 mM) and high (60 mM) concentrations of SrCl2. The transcription of the gene clusters annotated as hmyFCBA and czcCBADRS, coding for ion efflux pumps, was significantly induced following exposure to Sr, and not with Ca. There were also significant changes is the transcription of the genes encoding TctCBA proteins involved in citrate uptake and two hypothetical porin coding genes following exposure Sr and Ca. These results highlight a specific molecular response of bacterium Cupriavidus metallidurans CH34 to Sr, including the identification of putative Sr specific efflux pumps, and thus the potential of this bacterium to distinguish Sr from Ca. These findings will help to better understand natural Sr (and Ca) microbial weathering or mineralization processes in the environment, and could be of interest for bioremediation or bioprocessing of (radioactive) Sr-containing water, soil or waste. Two-condition experiments. Comparing samples after induction with metals (Sr, Ca) versus non-induced samples. Biological triplicate. Each array contains 3 technical replicates.

ORGANISM(S): Cupriavidus metallidurans CH34

SUBMITTER: Pieter Monsieurs

PROVIDER: E-GEOD-29863 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Background: The high number of heavy metal resistance genes in the soil bacterium Cupriavidus metallidurans CH34 makes it an interesting model organism to study microbial responses to heavy metals. Results: In this study the transcriptional response of this bacterium was measured after challenging it to a wide range of sub-lethal concentrations of various essential or toxic metals. Considering the global transcriptional responses for each challenge as well as by identifying the overlap in upregulated genes between different metal responses, the sixteen metals could be clustered in three different groups. Additionally, next to the assessment of the transcriptional response of already known metal resistance genes, new metal response gene clusters were identified. The majority of the metal response loci showed similar expression profiles when cells were exposed to different metals, suggesting complex cross-talk at transcriptional level between the different metal responses. The highly redundant nature of these metal resistant regions – illustrated by the large number of paralogous genes – combined with the phylogenetic distribution of these metal response regions within evolutionary related and other metal resistant bacteria, provides important insights on the recent evolution of this naturally soil dwelling bacterium towards a highly metal-resistant strain found in harsh and anthropogenic environments. Conclusions: The metal-resistant soil bacterium Cupriavidus metallidurans CH34 displays myriads of gene expression patterns when exposed to a wide range of heavy metals at non-lethal concentrations. The interplay between the different gene expression clusters points towards a complex cross-regulated regulatory network governing heavy metal resistance in C. metallidurans CH34. Keywords: Cupriavidus metallidurans CH34, transcriptional regulation, heavy metal resistance Two-condition experiments. Comparing samples after induction with heavy metals versus non-induced samples. Biological duplicate or triplicate. Each array contains 3 or 4 technical replicates.

Project description:Various environmental bacteria were adapted to the presence of toxic and recalcitrant organic solvents. Cupriavidus metallidurans CH34, a β-proteobacterium that was found in industrial environments is known as a bacterial model to study heavy metal resistance. Interestingly, genome screening of CH34 also reveals the existence of genes involved in the degradation of recalcitrant organic solvents, such acetone and aromatic compounds. Here, we showed that this bacterium could resist a large variety of organic solvents, and was also able to metabolize some of them. In particular, investigations were focused on acetone and isopropanol catabolism. Integrative studies based on transcriptomic (DNA microarrays), proteomic (2D-DIGE and Isotope-Coded Protein Label technology) and biochemical analyses (enzyme purification and characterization) showed a similar catabolic pathway for both molecules which involved the AcxABC acetone carboxylase. First, isopropanol is oxidized into acetone by the Adh alcohol dehydrogenase. Acetoacetate production from acetone is then catalyzed by the acetone carboxylase. The generated acetoacetate molecules are then transformed by the PacIJ 3-oxoacid CoA-transferase, to acetoacetyl-CoA and succinate. Finally, an acetyl-CoA acetyltransferase catalyses the hydrolysis of acetoacetyl-CoA into 2 acetyl-CoA that are introduced into the glyoxylate cycle. As demonstrated, key enzymes of the acetone/isopropanol catabolism (encoded by acx and ald genes) are under the control of a σ54-dependent RNA polymerase. Moreover, the catabolic pathway involved in acetone and isopropanol consumption was repressed when gluconate was given as alternative carbon substrate, displaying a new example of diauxie. The results presented here provide a comprehensive picture of acetone and isopropanol biodegradation in Cupriavidus metallidurans CH34 and strongly support the fact that CH34 can be considered as a solvent tolerant bacterium. Two-condition experiments. Comparing samples after induction with acetone versus non-induced samples. Biological triplicate. Each array contains 3 technical replicates.

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Cellular Response of the bacterium Cupriavidus metallidurans CH34 to Strontium: bio-precipitation as strontium carbonate.

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