Project description:To examine how the Arabidopsis root development responds to the Rhizobium sp. IRBG74 treatment at the molecular level, we performed RNA-seq experiments. Our RNA-seq results suggest that expression of genes mainly involved in auxin signaling, cell wall and cell membrane integrity and transport is altered in response to colonization by Rhizobium sp. IRBG74.
Project description:During the legume-rhizobium symbiosis, free-living soil bacteria known as rhizobia trigger the formation of root nodules. The rhizobia infect these organs and adopt an intracellular lifestyle within the symbiotic nodule cells where they become nitrogen-fixing bacteroids. Several legume lineages enforce their symbionts into an extreme cellular differentiation, comprising cell enlargement and genome endoreduplication. The antimicrobial peptide transporter BclA is a major determinant of this differentiation process in Bradyrhizobium sp. ORS285, a symbiont of Aeschynomene spp.. In the absence of BclA, Bradyrhizobium sp. ORS285 proceeds until the intracellular infection of nodule cells but the bacteria cannot differentiate into enlarged polyploid bacteroids and fix nitrogen. The nodule bacteria of the bclA mutant constitute thus an intermediate stage between the free-living soil bacteria and the intracellular nitrogen-fixing bacteroids. Metabolomics on whole nodules of Aeschynomene afraspera and Aeschynomene indica infected with the ORS285 wild type or the bclA mutant revealed 47 metabolites that differentially accumulated concomitantly with bacteroid differentiation. Bacterial transcriptome analysis of these nodules discriminated nodule-induced genes that are specific to differentiated and nitrogen-fixing bacteroids and others that are activated in the host microenvironment irrespective of bacterial differentiation and nitrogen fixation. These analyses demonstrated that the intracellular settling of the rhizobia in the symbiotic nodule cells is accompanied with a first transcriptome switch involving several hundreds of upregulated and downregulated genes and a second switch accompanying the bacteroid differentiation, involving less genes but that are expressed to extremely elevated levels. The transcriptomes further highlighted the dynamics of oxygen and redox regulation of gene expression during nodule formation and we discovered that bclA represses the expression of non-ribosomal peptide synthetase gene clusters suggesting a non-symbiotic function of BclA. Together, our data uncover the metabolic and gene expression changes that accompany the transition from intracellular bacteria into differentiated nitrogen-fixing bacteroids.
Project description:Metagenomic sequencing provides a window into microbial community structure and metabolic potential; however, linking these data to exogenous metabolites that microorganisms process and produce (the exometabolome) remains challenging. Previously, we observed strong exometabolite niche partitioning among bacterial isolates from biological soil crust (biocrust). Here we examine native biocrust to determine if these patterns are reproduced in the environment. Overall, most soil metabolites display the expected relationship (positive or negative correlation) with four dominant bacteria following a wetting event and across biocrust developmental stages. For metabolites that were previously found to be consumed by an isolate, 70% are negatively correlated with the abundance of the isolate’s closest matching environmental relative in situ, whereas for released metabolites, 67% were positively correlated. Our results demonstrate that metabolite profiling, shotgun sequencing and exometabolomics may be successfully integrated to functionally link microbial community structure with environmental chemistry in biocrust.
Project description:The survival, pollutant degradation activity and transcriptome response was monitored in Sphingomonas sp. LH128 inoculated into soil. Cultivable cell numbers were determined by plating, while phenanthrene degradation was monitored by HPLC. The genetic base for the adaptive strategy of LH128 in soil was investigated by using microarray consisting 7,200 gene-coding ORFs. During 4 hours of incubation, 510 genes were differentially expressed (317 increased and 193 reduced expression) while 610 genes were differentially expressed (318 increased and 292 reduced) after 10 days of incubation. Genes with increased expression comprised of gene encoding PAH catabolic enzymes, stress resistance, oxidative stress tolerance, outer membrane proteins/porins and efflux pump proteins while the downregulated genes comprised of genes encoding flagellar biosynthesis, ribosomal proteins and ATPase. Transcriptomic response of phenanthrene degrading Sphingomonas sp. LH128 inoculated into phenanthrene contaminated soil after 4h and after 10 days of incubation was studied using genome-wide gene expression analysis. For this purpose, the strain was pregrown in minimal medium and inoculated at appropriated celld densitites. RNA was extracted both from soil and and from initial inoculum and cDNA was synthesized and labeled with Cy3. Transcriptomic response in soil of three replicates per conditions after both incubation duration were analyzed and compared with the initial inoculum
Project description:The survival, pollutant degradation activity and transcriptome response was monitored in Sphingomonas sp. LH128 inoculated into soil. Cultivable cell numbers were determined by plating, while phenanthrene degradation was monitored by HPLC. The genetic base for the adaptive strategy of LH128 in soil was investigated by using microarray consisting 7,200 gene-coding ORFs. During 4 hours of incubation, 510 genes were differentially expressed (317 increased and 193 reduced expression) while 610 genes were differentially expressed (318 increased and 292 reduced) after 10 days of incubation. Genes with increased expression comprised of gene encoding PAH catabolic enzymes, stress resistance, oxidative stress tolerance, outer membrane proteins/porins and efflux pump proteins while the downregulated genes comprised of genes encoding flagellar biosynthesis, ribosomal proteins and ATPase.