Unknown,Transcriptomics,Genomics,Proteomics

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INTERACTIONS BETWEEN CYANOBACTERIA AND HETEROTROPHS UNDER DIFFERENT TROPHIC CONDITIONS

ABSTRACT: Application of genome-scale 'omics approaches to dissect subcellular pathways and regulatory networks governing interspecies interactions is dependent, at least initially, on the availability of model systems with well-annotated genomes and tractable genetics. We employed controlled cultivation and next-generation sequencing technology to identify transcriptional responses of euryhaline unicellular cyanobacterium Synechococcus sp. PCC 7002 and a marine facultative aerobe Shewanella putrefaciens W3-18-1 to investigate the effect of C sources and C flux directions on the interactions between these organisms.

ORGANISM(S): Synechococcus sp. PCC 7942

SUBMITTER: Lye Meng Markillie

PROVIDER: E-GEOD-53360 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Through chemical contamination of natural environments, microbial communities are exposed to many different types of chemical stressors; however, research on whole genome responses to this contaminant stress is limited. This study examined the transcriptome response of a common soil bacterium, Pseudomonas aeruginosa, to the common environmental contaminant pentachlorophenol (PCP). Cells were grown in chemostats at a low growth rate to obtain substrate-limited, steady-state, balanced-growth conditions. The PCP stress was administered as a continuous increase in concentration, and samples taken over time were examined for physiological function changes with whole cell acetate uptake rates (WAUR) and cell viability, and for gene expression changes using Affymetrix GeneChip technology and RT-PCR. Cell viability, measured by heterotrophic plate counts, showed a moderately steady decrease after exposure to the stressor, but WAURs did not change in response to PCP. In contrast to the physiological data, the microarray data showed significant changes in the expression of several genes. In particular, genes coding for multi-drug efflux pumps, including MexAB-OprM, were strongly upregulated. The upregulation of these efflux pumps protected the cells from the potentially toxic effects of PCP, allowing the physiological whole-cell function to remain constant. Experiment Overall Design: Cells of P. aeruginosa were grown in steady-state nutrient-limiting conditions using a minimal medium with acetate as the sole carbon source. PCP was added as a continuous input, and the samples were taken at timepoints corresponding to approximately 0.5, 1, and 2 generation times. Reactors were run at least in triplicate, and samples from duplicate WT reactors and a single RpoS- reactor were used for the microarrays. Gene expression is reported as the average fold-change associated with gene expression of PCP-shocked cells compared with the pre-PCP timepoint (0 hours) for the WT.

Project description:Hemicellulose, the second most abundant plant biomass fraction after cellulose, is widely viewed as a potential feedstock for the production of liquid fuels and other value-added materials. Degradation of hemicellulose by filamentous fungi requires production of many different enzymes, which are induced by biopolymers or its derivatives and regulated mainly at the transcriptional level through transcription factors (TFs). Neurospora crassa has been shown to express and secrete plant cell wall associated enzymes. To better understand genes specifically associated with degradation of hemicellulose, we identified 353 genes by transcriptome analysis of N. crassa wild type strain grown on beechwood xylan. Exposure to xylan induces 9 of the 19 predicted hemicellulase genes. The xylanolytic phenotype of strains with deletions in genes identified from the secretome and transcriptome analysis of wild type showed that none were essential for growth on beechwood xylan. The transcription factor XlnR/Xyr1 in Aspergillus and Trichoderma species is considered to be the major transcriptional regulator of genes encoding both cellulases and hemicellulases. We identified a xlnR/xyr1 homolog in N. crassa, NCU06971, termed xlr-1 (xylanase regulator 1). Deletion of xlr-1 in N. crassa abolishes the growth on xylan and xylose, but growth on cellulose was indistinguishable from wild type. To determine regulatory mechanisms associated with hemicellulose degradation, we explored the transcriptional regulon of XLR-1 under xylose and xylanolytic versus cellulolytic conditions. XLR-1 regulated only some predicted hemicellulase genes in N. crassa and was required for a full induction of several cellulase genes. Hemicellulase gene expression was induced by a combination of release from carbon catabolite repression (CCR) and induction. However, in N. crassa, xlr-1 is subject to non-CRE-1 mediated CCR. This systematic analysis provides the similarities and differences of hemicellulose degradation and regulation mechanisms used by N. crassa in comparison to other filamentous fungi. Four-condition experiments (minimal medium, xylan medium,xylose and Avicel medium) of mutant strain(xlr-1) compared to wild type strain; Cy3 and Cy5 dye swap

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INTERACTIONS BETWEEN CYANOBACTERIA AND HETEROTROPHS UNDER DIFFERENT TROPHIC CONDITIONS

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