A comparative analysis of exopolysaccharide and phytohormone secretions by four drought-tolerant rhizobacterial strains and their impact on osmotic-stress mitigation in Arabidopsis thaliana

Ghosh, Daipayan; Gupta, Anshika; Mohapatra, Sridev

doi:10.1007/s11274-019-2659-0

Cited by 124 publications

(74 citation statements)

References 90 publications

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“…The EPS production was recorded to be higher in B. megaterium PB50, followed by B. altitudinis PB46 and B. endophyticus PB3. Similarly, the increased production of EPSs under osmotic stress was reported in B. endophyticus [38]. Hence, our bacterial strains possibly could colonize on the surface of rice leaf and thrive under abiotic stress conditions.…”

Section: Discussionsupporting

confidence: 79%

Mitigation of drought stress in rice crop with plant growth‐promoting abiotic stress‐tolerant rice phyllosphere bacteria

Sabarinathan

Gomathy

et al. 2020

J Basic Microbiol

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In the search of effective drought‐alleviating and growth‐promoting phyllosphere bacteria, a total of 44 bacterial isolates were isolated from the leaf surface of drought‐tolerant rice varieties, Mattaikar, Nootripattu, Anna R(4), and PMK3, and screened for their abiotic stress tolerance by subjecting their growth medium to temperature, salinity, and osmotic stress. Only eight isolates were found to grow and proliferate under different abiotic stress conditions. These isolates were identified using 16S ribosomal DNA gene sequence and submitted to the NCBI database. All the bacterial isolates were identified as Bacillus sp., except PB24, which was identified as Staphylococcus sp., and these isolates were further screened for plant growth‐promoting (PGP) traits such as IAA production, GA production, ACC deaminase activity, and exopolysaccharide production under three different osmotic stress conditions adjusted using polyethylene glycol (PEG 6000). Additionally, mineral solubilization was measured under the normal condition. Bacillus endophyticus PB3, Bacillus altitudinis PB46, and Bacillus megaterium PB50 were found to have multifarious PGP traits. Consecutively, the performance of an individual strain to improve the plant growth was investigated under the osmotic stress (25% PEG 6000) and nonstress condition by inoculating them into rice seeds using hydroponics culture. Furthermore, the drought‐alleviating potency of bacterial strains was assessed in the rice plants using pot experiment (−1.2 MPa) through bacterial foliar application during the reproductive stage. Finally, as a result of seed inoculation and foliar spray, the application of B. megaterium PB50 significantly improved the plant growth under osmotic stress, protected plants from physical drought through stomatal closure, and improved carotenoid, total soluble sugars, and total protein content. Metabolites of PB50 were profiled under both stress and nonstress conditions using gas chromatography–mass spectroscopy.

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Section: Discussionsupporting

confidence: 79%

Mitigation of drought stress in rice crop with plant growth‐promoting abiotic stress‐tolerant rice phyllosphere bacteria

Sabarinathan

Gomathy

et al. 2020

J Basic Microbiol

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“…Bacterial EPS production is an important salt-tolerant characteristic which is always associated with biofilm production. Exopolysaccharides are able to lessen the hostile effect of osmotic-stress by augmenting fresh weight, dry weight and water content in plants [32]. All these salt-tolerance characteristics were supported by the SEM observation, which showed the bacterial ability to produce EPS, flocculate and biofilm formation when exposed to the saline condition as compared to non-saline media.…”

Section: Discussionmentioning

confidence: 67%

Characterization of salt-tolerant plant growth-promoting rhizobacteria and the effect on growth and yield of saline-affected rice

et al. 2020

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In this study, we characterized, identified, and determined the effect of salt-tolerant PGPR isolated from coastal saline areas on rice growth and yield. A total of 44 bacterial strains were isolated, and 5 were found to be tolerant at high salt concentration. These isolates were further characterized for salinity tolerance and beneficial traits through a series of quantitative tests. Biochemical characterization showed that bacterial survivability decreases gradually with the increase of salt concentration. One of the strains, UPMRB9, produced the highest amount of exopolysaccharides when exposed to 1.5M of NaCl. Moreover, UPMRB9 absorbed the highest amount of sodium from the 1.5M of NaCl-amended media. The highest floc yield and biofilm were produced by UPMRE6 and UPMRB9 respectively, at 1M of NaCl concentration. The SEM observation confirmed the EPS production of UPMRB9 and UPMRE6 at 1.5M of NaCl concentration. These two isolates were identified as Bacillus tequilensis and Bacillus aryabhattai based on the 16S rRNA gene sequence. The functional group characterization of EPS showed the presence of hydroxyl, carboxyl, and amino groups. This corresponded to the presence of carbohydrates and proteins in the EPS and glucose was identified as the major type of carbohydrate. The functional groups of EPS can help to bind and chelate Na + in the soil and thereby reduces the plant's exposure to the ion under saline conditions. The plant inoculation study revealed significant beneficial effects of bacterial inoculation on photosynthesis, transpiration, and stomatal conductance of the plant which leads to a higher yield. The Bacillus tequilensis and Bacillus aryabhattai strains showed good potential as PGPR for salinity mitigation practice for coastal rice cultivation.

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“…The IAA facilitates cell division, elongation, and differentiation while GA and ABA act as a signaling molecule in plants facing stress conditions [45]. Synthesis of these hormones by bacterial strains imparts stress tolerance in plants [46].…”

Section: Discussionmentioning

confidence: 99%

Exopolysaccharides Producing Bacteria for the Amelioration of Drought Stress in Wheat

et al. 2020

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This research was designed to elucidate the role of exopolysaccharides (EPS) producing bacterial strains for the amelioration of drought stress in wheat. Bacterial strains were isolated from a farmer’s field in the arid region of Pakistan. Out of 24 isolated stains, two bacterial strains, Bacillus subtilis (Accession No. MT742976) and Azospirillum brasilense (Accession No. MT742977) were selected, based on their ability to produce EPS and withstand drought stress. Both bacterial strains produced a good amount of EPS and osmolytes and exhibited drought tolerance individually, however, a combination of these strains produced higher amounts of EPS (sugar 6976 µg/g, 731.5 µg/g protein, and 1.1 mg/g uronic acid) and osmolytes (proline 4.4 µg/mg and sugar 79 µg/mg) and significantly changed the level of stress-induced phytohormones (61%, 49% and 30% decrease in Indole Acetic Acid (IAA), Gibberellic Acid (GA), and Cytokinin (CK)) respectively under stress, but an increase of 27.3% in Abscisic acid (ABA) concentration was observed. When inoculated, the combination of these strains improved seed germination, seedling vigor index, and promptness index by 18.2%, 23.7%, and 61.5% respectively under osmotic stress (20% polyethylene glycol, PEG6000). They also promoted plant growth in a pot experiment with an increase of 42.9%, 29.8%, and 33.7% in shoot length, root length, and leaf area, respectively. Physiological attributes of plants were also improved by bacterial inoculation showing an increase of 39.8%, 61.5%, and 45% in chlorophyll a, chlorophyll b, and carotenoid content respectively, as compared to control. Inoculations of bacterial strains also increased the production of osmolytes such asproline, amino acid, sugar, and protein by 30%, 23%, 68%, and 21.7% respectively. Co-inoculation of these strains enhanced the production of antioxidant enzymes such as superoxide dismutase (SOD) by 35.1%, catalase (CAT) by 77.4%, and peroxidase (POD) by 40.7%. Findings of the present research demonstrated that EPS, osmolyte, stress hormones, and antioxidant enzyme-producing bacterial strains impart drought tolerance in wheat and improve its growth, morphological attributes, physiological parameters, osmolytes production, and increase antioxidant enzymes.

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A comparative analysis of exopolysaccharide and phytohormone secretions by four drought-tolerant rhizobacterial strains and their impact on osmotic-stress mitigation in Arabidopsis thaliana

Cited by 124 publications

References 90 publications

Mitigation of drought stress in rice crop with plant growth‐promoting abiotic stress‐tolerant rice phyllosphere bacteria

Mitigation of drought stress in rice crop with plant growth‐promoting abiotic stress‐tolerant rice phyllosphere bacteria

Characterization of salt-tolerant plant growth-promoting rhizobacteria and the effect on growth and yield of saline-affected rice

Exopolysaccharides Producing Bacteria for the Amelioration of Drought Stress in Wheat

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