Project description:To address the question of how photosynthetic bacterium Rhodopseudomonas palustris differentially regulates gene expression of three nitrogenase isozymes (Mo, V, and Fe nitrogenases), we constructed Mo strain (Mo nitrogenase only strain), V strain (V nitrogenase only strain), and Fe strain (Fe nitrogenase only strain), and analyzed the whole genome transcriptome profiles of each mutant and wild-type cells grown under nitrogen-fixing conditions. Keywords: Genetic modification
Project description:To address the question of how photosynthetic bacterium Rhodopseudomonas palustris differentially regulates gene expression of three nitrogenase isozymes (Mo, V, and Fe nitrogenases), we constructed Mo strain (Mo nitrogenase only strain), V strain (V nitrogenase only strain), and Fe strain (Fe nitrogenase only strain), and analyzed the whole genome transcriptome profiles of each mutant and wild-type cells grown under nitrogen-fixing conditions. RNA was isolated from various Rhodopseudomonas palustris strains that were grown to the mid-logarithmic phase of growth. Fluorescently labeled cDNA was prepared by direct incorporation of either Cy3-dCTP or Cy5-dCTP during a first-strand reverse transcription reaction. The hybridization mixtures containing the two labeled cDNA samples to be compared were applied to microarray slides that had been covered with Lifterslips (Erie Scientific Company, Portsmouth, NH). The slides were assembled with hybridization chambers (Corning, Corning, NY) and submerged in a 65ºC water bath. After 14-16 h of hybridization, the slides were washed and scanned with a ScanArray 4000XL scanner (PerkinElmer, Boston, MA). Images (Cy3 and Cy5) were captured as TIFF files and were analyzed with the image processing software ImaGene version 5.6 (BioDiscovery, Inc., El Segundo, CA). The software package lcDNA was used for data normalization and assessment of the statistical confidence intervals of gene expression. Duplicate calibration experiments and three comparative experiments using RNA from three separately grown cultures (three biological replicates) with duplicate slides for each (10 slides in total) were used to generate each data set.
Project description:Facultative phototrophic bacteria are excellent models for analyzing the coordination of major metabolic traits including oxidative phosphorylation, photophosphorylation, carbon dioxide fixation and nitrogen fixation. In Rhodobacter sphaeroides and R. capsulatus, a two-component system called RegBA (PrrBA) controls these functions and it has been thought that this redox sensing regulatory system was essential for coordinating electron flow and could not be easily replaced in facultative phototrophs. Here we show that this is not the case and that the oxygen-sensing FixlJ-K system, initially described in rhizobia, controls microaerobic respiration, photophosphorylation and several other metabolic traits in Rhodopseudomonas palustris. A R. palustris fixK mutant grew normally aerobically but was impaired in microaerobic growth. It was also severely impaired in photosynthetic growth and has very little bacteriochlorophyll. Transcriptome analyses indicated that FixK positively regulates heme and bacteriochlorophyll biosynthesis, cbb3 oxidase and NADH dehydrogenase genes, as well as genes for hydrogen uptake, iron oxidation, and aromatic compound degradation. Electrophoretic mobility shift assays showed that FixK binds directly to the promoters of a bacteriochlorophyll biosynthesis operon, a bacteriophytochrome-histidine kinase gene and the fnr-type regulatory gene, aadR. AadR is likely responsible for mediating some indirect effects of FixK on expression of anaerobic genes. These results underscore that physiologically similar bacteria can use very different regulatory strategies to control common major metabolisms.
Project description:Facultative phototrophic bacteria are excellent models for analyzing the coordination of major metabolic traits including oxidative phosphorylation, photophosphorylation, carbon dioxide fixation and nitrogen fixation. In Rhodobacter sphaeroides and R. capsulatus, a two-component system called RegBA (PrrBA) controls these functions and it has been thought that this redox sensing regulatory system was essential for coordinating electron flow and could not be easily replaced in facultative phototrophs. Here we show that this is not the case and that the oxygen-sensing FixlJ-K system, initially described in rhizobia, controls microaerobic respiration, photophosphorylation and several other metabolic traits in Rhodopseudomonas palustris. A R. palustris fixK mutant grew normally aerobically but was impaired in microaerobic growth. It was also severely impaired in photosynthetic growth and has very little bacteriochlorophyll. Transcriptome analyses indicated that FixK positively regulates heme and bacteriochlorophyll biosynthesis, cbb3 oxidase and NADH dehydrogenase genes, as well as genes for hydrogen uptake, iron oxidation, and aromatic compound degradation. Electrophoretic mobility shift assays showed that FixK binds directly to the promoters of a bacteriochlorophyll biosynthesis operon, a bacteriophytochrome-histidine kinase gene and the fnr-type regulatory gene, aadR. AadR is likely responsible for mediating some indirect effects of FixK on expression of anaerobic genes. These results underscore that physiologically similar bacteria can use very different regulatory strategies to control common major metabolisms. Comparison of transcription profiles of Rhodopseudomonas palustris wild type and fixK mutant grown microaerobically.
Project description:The underlying adaptations required by anoxygenic phototrophs to oxidize Fe(II), a potential stressor, are not well constrained. We used quantitative proteomics to compare cells of the photoferrotroph Rhodopseudomonas palustris TIE-1 grown photoautotrophically with Fe(II) or H2, and photoheterotrophically with acetate. We observed unique proteome profiles for each condition with differences primarily driven by carbon source. Growth on Fe(II) was characterized by a response typical of iron homeostasis which included an increased abundance of proteins required for metal efflux (particularly copper), and decreased abundance of iron import proteins, including siderophore receptors, with no evidence of further stressors such as oxidative damage. This study suggests that the main challenge facing photoferrotrophs comes from limitations imposed by autotrophic growth and, once this challenge is overcome, iron stress can be mitigated using iron management mechanisms common to diverse bacteria.
Project description:Rhodopseudomonas palustris strain SA008.1.07 can use syringic acid as sole organic carbon source anaerobically. Grew all anaerobically in various carbon sources: syringic acid, succinate, and p-hydroxybenzoic acid.
Project description:Rhodopseudomonas palustris is a species of purple phototrophic bacterium. In these species, solar energy is captured by reaction centre-light harvesting 1 (RC-LH1) complexes which reside in membranes within the cells. The RC comprises three protein subunits: H, M, L and is encircled by a ring of LH1-α and LH1-β subunit pairs. Approximately 10% of these complexes in the wild-type (WT) strain include an additional subunit called protein-W. In this project, we have determined cryo-EM structures for RC-LH1 complexes both with and without protein-W. To enable the purification of RC-LH1-W with 100% occupancy of protein-W, strain expressing a C-terminally His-tagged W was engineered. For complexes lacking W, a knockout strain was used. Proteomic analysis was employed to validate these strains and establish that the WT and W-His expressed similar levels of W relative to RC-LH1.