Project description:Hydroxyproline in decaying organic matter and root exudates and is a source of carbon and nitrogen to soil-dwelling microorganisms. A bacterial pathway for hydroxyproline catabolism was elucidated over 30 years ago however genes and gene function relationships were not established. In that pathway, trans-4-hydroxy-L-proline (4-L-Hyp) is epimerized to cis-4-hydroxy-D-proline (4-D-Hyp), and then, in three enzymatic reactions, the D-diastereomer is converted via 1-pyrroline-4-hydroxy-2-carboxylate and alpha-ketoglutaric semialdehyde to alpha-ketoglutaric acid. Here we report on the regulation and functions of several genes from a hydroxyproline catabolism locus on the pSymB megaplasmid of the legume endosymbiont Sinorhizobium meliloti. The hydroxyproline catabolism genes (hyp) are negatively regulated by hypR and are organized as four single transcripts (hypR, hypD, hypS and hypH) and a 9 gene transcript (hypMNPQ(RE)XYZ). Transcription of these genes was induced in the presence of either 4-L-Hyp and 4-D-Hyp, and was not subject to nitrogen source regulation. The hypRE gene is shown to encode 4-hydroxyproline 2-epimerase (HypRE) responsible for the reversible isomerization of 4-L-Hyp and 4-D-Hyp, whereas a hypRE mutant grew with 4-D-Hyp but not of 4-L-Hyp as carbon source. hypO, hypD and hypH are predicted to encode the 4-D-Hyp oxidase, the 1-pyrroline-4-hydroxy-2-carboxylate deaminase and alpha-ketoglutaric semialdehyde dehydrogenase respectively. No epimerase activity was detected for the HypY (Smb20270), a predicted racemase, and activities from four other genes (designated hypS, hypX and hypZ) remain to be determined. In summary, the 4-hydroxyproline (4-Hyp) catabolic pathway for S. meliloti is similar to that previously elucidated for Pseudomonas however the presence of additional genes at the hyp locus suggests that additional metabolic steps still remain to be elucidated.
Project description:The Alphaproteobacterium Sinorhizobium meliloti lives in soil and is capable of fixing molecular nitrogen in symbiosis with legume plants. In this work, the small proteome of S. meliloti strain 2011 was studied to uncover translation of both annotated and novel small open reading frame (sORF)-encoded proteins (SEPs).
Project description:We characterized transcriptomes of a Sinorhizobium meliloti wild type strain (CL150) expressing either Ca. Liberibacter asiaticus ctrA or Sinorhizobium meliloti ctrA
Project description:We characterized transcriptomes of a Sinorhizobium meliloti rpoH1rpoH2 deletion mutant (RFF231; Lang et al. 2018, mSphere 3:e00454-18) expressing either Ca. Liberibacter asiaticus rpoH or Sinorhizobium meliloti rpoH1
Project description:This experiment studies the effect of purified Sinorhizobium meliloti Nodulation factors (Nod-factors, NF) on gene expression in the model legume Medicago truncatula.
Project description:Sinorhizobium meliloti lives as a soil saprophyte, and engages in a nitrogen fixing symbiosis with plant roots. To succeed in such diverse environments, the bacteria must continually adjust gene expression. Transcriptional plasticity in eubacteria is often mediated by alternative sigma factors interacting with core RNA polymerase. The S. meliloti genome encodes 14 of these alternative sigmas, including 11 extracytoplasmic function (ECF) sigmas. We used custom Affymetrix Symbiosis Chips to characterize the global transcriptional response of S. meliloti overexpressing the ECF sigma factor, RpoE2. Our work identifies over 200 genes whose expression is dependent on RpoE2.
Project description:Sinorhizobium meliloti can live as a soil saprophyte, and can engage in a nitrogen fixing symbiosis with plant roots. To succeed in such diverse environments, the bacteria must continually adjust gene expression. Transcriptional plasticity in eubacteria is often mediated by alternative sigma factors interacting with core RNA polymerase. The S. meliloti genome encodes 14 of these alternative sigmas, including two putative RpoH (heat shock) sigmas. We used custom Affymetrix Symbiosis Chips to characterize the global transcriptional response of S. meliloti rpoH1, rpoH2 and rpoH1 rpoH2 mutants during heat shock and stationary phase growth. Under these conditions, expression of over 300 genes is dependent on rpoH1 and rpoH2.
