Depletion of BamA activates the RSI circuit in S. meliloti
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ABSTRACT:
PROVIDER: PRJNA817812 | ENA |
REPOSITORIES: ENA
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Project description:The symbiotic relationship between the alpha-proteobacterium S. meliloti and the legume M. truncatula has been extensively studied. However, stress response mechanisms vital to bacterial survival and adaptation are as yet poorly understood. In this study, we sought to characterize the response of S. meliloti to depletion of essential outer membrane protein BamA, which is predicted to cause a loss of outer membrane integrity and an accumulation of unfolded proteins in the periplasm. A total of 132 differentially expressed genes were detected, with 74 genes up-regulated and 58 genes down-regulated. The transcriptomic response to BamA depletion shares similarities to those observed during activation of the RSI circuit, which plays a role in mitigating loss of viability in response to this stress. Induction of genes in the RSI regulon is likely due to a loss of negative regulator ExoR during BamA depletion. The two-component stress response system CpxRA and regulator CpxP also were found to affect the response to BamA depletion.
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Project description:We wanted to test the effect on global gene expression of depleting the essential cell cycle regulator CtrA in order to determine the genes both indirectly and directly transcriptionally regulated by CtrA Gene expression changes in S. meliloti 1,2,4 and 6 hours post CtrA depletion Log-phase S. meliloti cultures carrying an IPTG-inducible allele of CtrA were split and transferred to growth media lacking IPTG (depletion) and with 1mM IPTG (control). Samples for RNA extraction were taken 1,2,4, and 6 hours after the start of the depletion experiment to monitor gene expression changes in the population after different periods of CtrA depletion.
2015-04-24 | E-GEOD-68218 | biostudies-arrayexpress
Project description:We wanted to test the effect on global gene expression of depleting the essential cell cycle regulator CtrA in order to determine the genes both indirectly and directly transcriptionally regulated by CtrA Gene expression changes in S. meliloti 1,2,4 and 6 hours post CtrA depletion
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Project description:Endospore formation in Firmicutes is a complex morphological process triggered by environmental stress. At the end of this process, a mature spore containing the condensed genome is released through lysis of the mother cell. The mature spore is encased by several protective layers, including an inner and an outer spore membrane (IsM and OsM, respectively), both derived from the inner membrane (IM) of the mother cell. While this process is well understood in monoderm bacteria like Bacillus subtilis, less is known about diderm spore-formers such as Acetonema longum, which retain and remodel their OsM into a true outer membrane (OM) during germination. Our results show that outer membrane proteins (OMPs), including the essential β-barrel Assembly Machinery (BAM) component BamA, are present in vegetative and germinating cells but absent from mature spores. These observations highlight an unprecedented mechanism of inner to outer membrane remodelling in the absence of BamA. Expression profiles of cells at different growth stages and phylogenomic analyses identified two novel proteins, co-expressed and in an operon with BamA, that were highly conserved among diderm Firmicutes: a β-barrel OMP containing three polypeptide transport-associated (POTRA) domains (SonA) and a putative OM lipoprotein (SonB). In vitro experiments further demonstrated that both BamA and SonA can self-insert into liposomes under physiological conditions. Together, we propose a model in which BamA and its functional partners, SonA and SonB, drive membrane remodelling during germination. The process is initiated by self-insertion of BamA, which then assists the folding and insertion of other OMPs, including LptD, progressively shifting the protein and lipid composition of the OsM to produce a true OM. Collectively, our findings provide new insights into the functional role of BamA in membrane remodelling during OM biogenesis.
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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.
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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.
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Project description:Sinorhizobium meliloti, a facultative microsymbiont of alfalfa, should fine-tune its cellular processes to live saprophytically in soils characterized with limited nutrients and diverse stresses. In this study, TiO2 enrichment and LC-MS/MS were used to uncover the site-specific Ser/Thr/Tyr phosphoproteome of S. meliloti in minimum medium at stationary phase. There are a total of 96 unique phosphorylated sites, with a Ser/Thr/Tyr distribution of 65:32:5, in 78 proteins. Phosphoproteins identified in S. meliloti showed a wide distribution pattern regarding to functional categories, such as replication, transcription, translation, posttranslational modification, transport and metabolism of amino acids, carbohydrate, inorganic ion, succinoglycan etc. Ser/Thr/Tyr phosphosites identified within the conserved motif in proteins of key cellular function indicate a crucial role of phosphorylation in modulating cellular physiology. Moreover, phosphorylation events potentially involved in rhizobial adaptation to diverse stresses were also discussed, such as those identified in SMa0114 and PhaP2 (polyhydroxybutyrate synthesis), ActR (pH stress and microaerobic adaption), SupA (potassium stress), chaperonin GroEL2 (viability and potentially symbiosis), and ExoP (succinoglycan synthesis and secretion). These Ser/Thr/Tyr phosphosites identified herein would be helpful for our further investigation and understanding of the role of phosphorylation in rhizobial physiology.
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