Abstract
Salinity stress is one of the serious factors, limiting production of major agricultural crops; especially, in sodic soils. A number of approaches are being applied to mitigate the salt-induced adverse effects in agricultural crops through implying different halotolerant microbes. In this aspect, a halotolerant, Exiguobacterium profundum PHM11 was evaluated under eight different salinity regimes; 100, 250, 500, 1000, 1500, 2000, 2500, and 3000 mM to know its inherent salt tolerance limits and salt-induced consequences affecting its natural metabolism. Based on the stoichiometric growth kinetics; 100 and 1500 mM concentrations were selected as optimal and minimal performance limits for PHM11. To know, how salt stress affects the expression profiles of regulatory genes of its key metabolic pathways, and total production of important metabolites; biomass, carotenoids, beta-carotene production, IAA and proline contents, and expression profiles of key genes affecting the protein folding, structural adaptations, transportation across the cell membrane, stress tolerance, carotenoids, IAA and mannitol production in PHM11 were studied under 100 and 1500 mM salinity. E. profundum PHM11 showed maximum and minimum growth, biomass and metabolite production at 100 and 1500 mM salinity respectively. Salt-induced fine-tuning of expression profiles of key genes of stress pathways was determined in halotolerant bacterium PHM11.
Highlights
Exiguobacterium, a well known halotolerant bacteria, has been attracting most of the researchers as being a vital agent of salinity stress mitigation and an important source of useful carotenoids (Rodrigues et al, 2008)
Based on the obtained BLASTn analysis, indent score, BLAST score, ‘E’ value, and query coverage for 16S rRNA gene, bacterium PHM11 was identified as Exiguobacterium profundum PHM11
2.5 × 109 cells of PHM11 were inoculated in nutrient broth (NB) alone, and with supplementation of 100 and 1500 mM sodium chloride salt, and grown for 72 h, until it reached to initial stationary phase
Summary
Exiguobacterium, a well known halotolerant bacteria, has been attracting most of the researchers as being a vital agent of salinity stress mitigation and an important source of useful carotenoids (Rodrigues et al, 2008). A number of transcriptomic studies of plants inoculated with endophytes and plant growth promoting rhizobacteria have been done and still ongoing; there is a long research gap in knowing that how these useful halotolerant bacteria are fine-tuning their gene expression profiles to acclimatize, and what physiological changes are happening that alternatively promoting their survival under salinity. A halotolerant E. profundum PHM11 bacterium was isolated and characterized for different plant growth promotion traits and tested for the changes in its physiology and gene expression patterns under salinity. Efforts were made to get the salt-induced changes in the physiology and gene expression profiles of PHM11 under salinity that alternatively affect its survival, stress mitigation efficiency, and plant growth promotion potential
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