Unknown,Transcriptomics,Genomics,Proteomics

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RNA-seq analysis of polyhydroxyalkanoate-producing Ralstonia eutropha H16

ABSTRACT: Ralstonia eutropha H16 is well-known to produce poly(3-hydroxybutyrate) [P(3HB)], a kind of polyhydroxyalkanoates attracted as bio-based biodegradable plastics, efficiently as an energy storage material under unbalanced growth conditions. To obtain further extended knowledge of PHA biosynthesis, this study employed quantitative transcriptome analysis based on deep sequencing of complementary DNA generated from RNA (RNA-seq) for R. eutropha H16. Total RNAs were extracted from R. eutropha cells in growth, PHA production, and stationary phases on fructose. rRNAs in the preparation were removed by repeated treatments with magnetic beads specific to bacterial rRNAs, and then the 36 bp sequences were determined by using Illumina high-throughput sequencer. The RNA-seq results supported induction of gene expression for transcription, translation, cell division, peptidoglycan biosynthesis, pilus and flagella assembly, energy conservation, and fatty acid biosynthesis in growth phase, and repression trends for genes involved in central metabolisms in PHA production phase. Interestingly, transcription of genes for Calvin-Benson-Bassham (CBB) cycle and several selected genes for ?-oxidation were significantly induced in PHA production phase even when the cells were grown on fructose. mRNA profiles of R. eutropha H16 grown on fructose at different phases were generated by deep sequencing, in duplicate, using Illumina GAIIx.

ORGANISM(S): Ralstonia eutropha H16

SUBMITTER: Toshiaki Fukui

PROVIDER: E-GEOD-47759 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Clostridium ljungdahlii derives energy by acetogenesis as a lithotrophic pathway and as part of various organotrophic pathways. Its recently sequenced genome has made it possible to discover changes in gene expression that occur in different growth modes, from which strategies for biofuel production may be developed. C. ljungdahlii was grown with fructose as an organoheterotrophic substrate and also lithoautotrophically, either on syngas or with H2 as the electron donor and CO2 as the electron acceptor. RNA extracted from all three conditions was analyzed by hybridization to a microarray, and gene expression was compared quantitatively by RNA-Seq of C. ljungdahlii grown with fructose and with H2 and CO2. Results. Strongly upregulated (> 10-fold, p < 0.05) genes with both syngas and H2/CO2 encode enzymes that degrade aspartate and arginine through the urea cycle to control the release of ammonia from amino acids. Numerous genes for uptake and degradation of peptides and amino acids, response to sulfur starvation, and molybdopterin-dependent pathways were also significantly (> 2-fold, p < 0.05) upregulated, along with three potentially NADPH-producing pathways for which the key metabolites are (S)-malate, ornithine and 6-phospho-D-gluconate. Upregulation of genes implicated in quorum sensing, sporulation and cell wall remodeling suggests a global and multicellular response to lithoautotrophic conditions. With syngas, (R)-lactate dehydrogenase and associated electron transfer flavoproteins were upregulated, representing a route of electron transfer from ferredoxin to NAD that is independent of the proton-translocating Rnf complex. With H2/CO2, a flavodoxin and histidine biosynthesis enzymes were upregulated. Genes for degradation of purine bases entering the cell by facilitated diffusion were upregulated in lithotrophic cells, whereas genes for degradation of adenine or adenosine derivatives entering by active transport were significantly (2-fold, p < 0.05) downregulated. The most downregulated genes, after those specific to fructose metabolism, encode enzymes of pyrimidine and purine biosynthesis, arginine fermentation to ornithine, threonine biosynthesis and phosphate uptake. Genes for biogenesis of an intracytoplasmic microcompartment were downregulated, within which (S)-1,2-propanediol dehydratase and other enzymes may dispose of methylglyoxal, a toxic byproduct of glycolysis, as 1-propanol. Several redox-active proteins, both cytoplasmic and membrane-associated, and predicted cell surface proteins were identified as differentially regulated. Conclusion. The transcriptomic profiles of C. ljungdahlii in lithoautotrophic and organoheterotrophic growth modes indicate large-scale physiological and metabolic differences, observations that may guide the production of biofuels and commodity chemicals with this species.

Project description:Transcriptomics analysis of biopolymer (medium chain length polyhydroxyalkanoate) producing strain P.putida LS46 cultured with biodiesel derived waste carbon sources: studies of cellular adaptation to the industrial waste streams and metabolic profiling under the polymer producing conditions. We are reporting RNAseq analysis data here as part of our multi-level Omics study of medium chain length polyhydroxyalkanoate (mcl-PHA) producing strain P.putida LS46 culture with biodiesel derived waste glycerol and waste fatty acids. The data presented here will be used in two separate manuscripts. The objectives of this study are a): to evaluate cellular responses of P.putida LS46 under industrial waste stream. b): to study gene expression profile under two selected mcl-PHA producing conditions of P.putida LS46. Comparative multi-level Omics study: for objective a): Exponential P.putida LS46 cell from waste glycerol culture compared against reagent grade pure glycerol culture. For objective b): Two mcl-PHA producing conditions, namely stationary phase waste glycerol culture and exponential phase waste fatty acid culture of P.putida LS46, were compared against exponential phase waste glycerol culture of P.putida LS46. Major results from objective a): The waste glycerol substrate induced expression of a large number of genes putatively involved in heavy metal tolerance, including three gene clusters: a putative cusABC transcript unit and two copies of copAB, which are usually involved in copper resistance and tolerance to other monovalent heavy metals. A local gene relocation was observed in cluster 1 consisting cusABC and copAB relative to the KT2440 type strain according to the phylogenetic and gene neighbourhood analyses on various P. putida strains. P. putida LS46 also contains 11 putative MerR family regulators, which sense various environmental stimuli including heavy metals. MerR-1 is an ortholog of the copper response regulator of other gram-negative bacteria, and was highly up-regulated in waste glycerol cultures. Finally, a number of genes involved in cell responses to high extra-cellular Na+ concentrations, and genes of the fatty acid beta-oxidation pathway were up-regulated in waste glycerol cultures Major results from objective b): Regardless to the type of substrates, up-regulation of two mcl-PHA synthase (PhaC1 and PhaC2), and two phasin proteins (PhaF and PhaI) are the most common genotype under mcl-PHA production conditions. PhaG and possible PhaJ4 connect fatty acid de novo synthesis to mcl-PHA in waste glycerol culture. Interestingly, expression of gene, fabZ, in production of unsaturated fatty acid from fatty acid de novo synthesis was only observed in waste glycerol culture. On the other hand, PhaJ1 and PhaJ4 derived mcl-PHA production via fatty acid beta-oxidation was observed under waste fatty acid culture. These results would help to explain observed different production kinetics and monomer distribution of the polymer. Although under active mcl-PHA production condition, depression on the expression of glpF genes in glycerol transportation system prevent further channelling extra-cellular glycerol into the cell. Waste glycerol culture also triggers trahalose synthesis pathway, a potential competing pathway during mcl-PHA synthesizing. In waste fatty acid culture, the intermediates (acyl-CoA and 3-hydroxyacyl-CoA) of fatty acid beta-oxidation were used for mcl-PHA production and were also likely hydrolysed to their free acid forms via an up-regulated thioesteras coding gene, tesA. Acetyl-CoA cleaved from the pathway was clearly channeled into glyoxylate shut for C2 carbon assimilation over spillage as CO2 through TCA cycle or used in fatty acid biosynthesis pathway. In total 4 sampling points, namely exponential phase of pure glycerol, waste glycerol and waste free fatty acids cultures, and stationary phase of waste glycerol culture. For each sampling point, 2 biological replicates were taken. (Thus 8 samples in total)

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RNA-seq analysis of polyhydroxyalkanoate-producing Ralstonia eutropha H16

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