Abstrait

PROTEOMIC AND METABOLOMIC ANALYSIS OF THE NTRC MUTANT AZOSPIRILLUM BRASILIENSE

Sudhansu Sekhar Patra

Bacterial chemotaxis enables mobile microorganisms to explore their surroundings in search of growth and survival niches. Chemotaxis relies on chemoreceptor signalling arrays that interact with cytoplasmic proteins to regulate the direction of movement at the molecular level. Two separate chemotaxis pathways, Che1 and Che4, mediate chemotaxis in Azospirillum brasilense. In the free-living and plant-associated lifestyles of A. brasilense, Che1 and Che4 are both essential. Here, we investigate the function of chemotaxis in A. brasilense physiology using whole-cell proteomics and metabolomics. We discovered that chemotaxis-unrelated processes, including as significant alterations in transcription, signalling trafficking, and cell metabolism, are impacted in mutants lacking either CheA1 or CheA4 or both. We uncover particular impacts of CheA1 and CheA4 on nitrogen metabolism, such as nitrate absorption and nitrogen fixation, which may be dependent, at the very least, on the transcriptional control of RpoN, which encodes RpoN, a worldwide regulator of metabolism, including nitrogen. We also find unique, as of yet uncharacterized, transcriptional and posttranscriptional regulatory layers for regulators of nitrogen metabolism. Our data show that CheA1 and CheA4 play important roles in chemotaxis and nitrogen metabolism, possibly by controlling global regulatory networks. Salttolerant materials responded to salt stress at the protein and metabolic levels more favourably than salt-sensitive materials did. These findings collectively imply that salt-tolerant germplasm may improve resilience through the repair of intracellular structures, stimulation of lipid metabolism, and elevation of osmotic metabolites. These findings offer fresh perspectives on how seeds respond to salt stress as well as new avenues for research into the molecular processes and metabolic homeostasis of seeds during the early abiotic stresses of germination