Assessment of Methylobacterium oryzae CBMB20 aggregates for salt tolerance and plant growth promoting characteristics for bio-inoculant development

Abstract

Salinity is one of the major factors contributing to the loss of crop productivity and thereby impacting livelihood of people in more than 100 countries of the world and the area of land affected by salinity is increasing day by day. This will worsen due to various factors such as drought that might result in high soil salinity. Use of plant growth promoting rhizobacteria is one of the promising eco-friendly strategies for salinity stress management as part of sustainable agricultural practices. However, it requires selecting rhizobacteria with good survivability and adaptation to salt stress. In this study we report aggregation of Methylobacterium oryzae CBMB20 cells grown in media containing high C/N ratio (30:1) than in media containing low C/N ratio (7:1). Aggregated Methylobacterium oryzae CBMB20 cells exhibited enhanced tolerance to UV irradiation, heat, desiccation, different temperature regimes, oxidative stress, starvation and supported higher population in media. Poly-β-hydroxybutyrate accumulation, exopolysaccharide production, proline accumulation and biofilm formation were good at 100 mM salt concentration with good microbial cell hydrophobicity at both 50 and 100 mM than other concentrations. Both the aggregated and non-aggregated cells grown under 0–200 mM salt concentrations produced IAA even at 200 mM salt concentration with a peak at 100 mM concentration with aggregated cells producing significantly higher quantities. ACC deaminase activity was observed in all NaCl concentrations studied with gradual and drastic reduction in aggregated and non-aggregated cells over increased salt concentrations.

Efficient rhizobacteria promote growth and alleviate NaCl-induced stress in the plant species Sulla carnosa

“…Several studies have tried to analyze the mechanisms by which bacteria can improve the resistance in plants. Hence, some research shows that the use of PGP bacteria can promote plant growth and enhance salt tolerance capacity by inducing synthesis of osmolytes (Siddikee et al, 2011;Chanratana et al, 2017;Karnwal, 2017;León et al, 2018). Our results revealed that after evaluation, we selected Acinetobacter sp.…”

“…Hence, it has been demonstrated that salt-tolerant PGP bacteria isolated from alkaline soil, are physiologically adapted to abiotic stresses and could increase salt tolerance capacity and the growth of various crop plants, such as tomato, maize, and pepper in saline soil conditions (Mayak et al, 2004;Ferreira et al, 2018;Yasin et al, 2018). In fact, efficient PGPR used to alleviate NaCl-induced stress must be obligatory resistant to this constraint, or their development will be inhibited by salt (Sharma et al, 2015;Upadhyay and Singh, 2015;Chanratana et al, 2017).…”

“…Previous studies have also reported that bacterial inoculants release metal-chelating substances in the host plant rhizosphere, such as iron-chelating siderophores may promote growth and enhance stress tolerance capacity by influencing the plant the uptake and bioavailability of various metal ions (Dimkpa et al, 2009). The use of ACC deaminase producing PGP-bacteria could be effective in promoting the growth of a variety of plants under various stressful conditions, such as flooding, heavy metals, high salinity and drought (Ghnaya et al, 2015;Chanratana et al, 2017;Maxton et al, 2017) by reducing the levels of the stress-hormone ethylene (Khan et al, 2018;Yasin et al, 2018).…”

Tailoring plant-associated microbial inoculants in agriculture: a roadmap for successful application

“…Moreover, different members of the Methylobacterium genus produce high levels of CKs and increase the tolerance of plants to abiotic stresses (e.g. salt and drought stress) ( Knief et al, 2012 ; Lee et al, 2015 ; Chanratana et al, 2017 ; Jorge et al, 2019 ).…”

Potentials, Utilization, and Bioengineering of Plant Growth-Promoting Methylobacterium for Sustainable Agriculture

“…M. nodulans Crotalaria providing nitrogen; decreasing levels of ethylene [12,16,17] M. oryzae Rice increasing plant cytokinin levels; solubilizing phosphate [13,[18][19][20] M. extorquens Pine; Arabidopsis; Brassia inducing the expression of host defense genes [21,22] M. mesophilicum Sugarcane increasing plant cytokinin levels [23] M. radiotolerans Brassia; Combretaceae providing nitrogen; exhibited high antibacterial and antifungal activity; decreasing levels of ethylene [24,25] M. populi Brassia providing nitrogen [26] M. komagatae Brassia providing nitrogen [17] M. aquaticum Brassia providing nitrogen [17] M. funariae Moss increasing plant cytokinin levels [27] M. phyllosphaerae Rice decreasing levels of ethylene [28]…”