Enterobacter sp. SE992-induced regulation of amino acids, sugars, and hormones in cucumber plants improves salt tolerance

Abstract

The rhizosphere of plants serves as a host for a number of microbiota. The mutualistic interaction between rhizosphere bacteria and plants supports the promotion of plant growth. These interactions also support responses against biotic and abiotic stresses through the modulation of plant metabolism. In the current study, we sought to investigate the effects of individual sugar, amino acid, and salicylic acid content upon cucumber plant salt tolerance with respect to Enterobacter sp. SE992 interactions. Enterobacter sp. SE992 was isolated from soil and identified through 16s rDNA sequences. Mechanisms of plant growth promotion were confirmed via tryptophan-dependent indole-3-acetic acid synthesis in bacterial culture medium. Salt tolerance of Enterobacter sp. SE992 was confirmed on bacterial media supplemented with 3 % NaCl. Greenhouse experiments revealed that soil salinity inhibited cucumber plant growth. However, inoculation of Enterobacter sp. SE992 into saline soil mitigated the adverse effects of salt stress, enhancing the length and biomass of shoots and roots. The concentrations of chlorophyll, sucrose, glucose, and fructose were decreased in salt-affected plants. Interaction with Enterobacter sp. SE992 resulted in the enhanced production of chlorophyll and sugars in stressed plants. Salinity correlated with a significant decrease in threonine, glutamine, cysteine, valine, methionine, isoleucine, tyrosine, phenylalanine, histidine, and arginine levels but stimulated the accumulation of glycine, alanine, leucine, and lysine. Treatment with Enterobacter sp. SE992 ameliorated these stress effects and increased the levels of all amino acids. Marked accumulation of salicylic acid was observed in salt-infected plants, while inoculation with Enterobacter sp. SE992 suppressed salicylic acid synthesis. Our findings suggest that inoculation of Enterobacter sp. SE992 in soil can promote plant growth and increase stress tolerance by positively influencing plant metabolism under conditions of high salinity.

Indoleacetic acid production and plant growth promoting potential of bacterial endophytes isolated from rice (Oryza sativa L.) seeds

“…The endophytic strain, when applied to tomato plants, significantly increased the plant growth and development and confirmed our findings. The plant growth enhancing potential, in terms of shoot and root length, fresh and dry biomass, and chlorophyll contents, were in line with Khan et al [20], Ullah et al [33], Kang et al [19], Wahyudi et al [34], and Spaepen et al [29]. It is now known that IAA can be produced by variety of endophytes [20].…”

“…To date, numerous studies have investigated using plant growth promoting rhizobacteria (PGPRs) to mitigate the adverse effects of stresses on crops [9,10,18,19,25,28]. Such endophytic bacteria colonize healthy plant tissues without causing any disease symptoms to the host plants.…”

“…2). Ullah et al [33] and Kang et al [19] also utilized this method to detect the IAA in the culture filtrate of entomopathogenic bacteria and PGPR, respectively. The differences in the IAA production ability of our selected isolates were in line with the findings of Cohen et al [7], Mutluru and Konada [27], and Boiero et al [4].…”

“…SE992) and negative (Escherichia coli KCCM 12119) controls, respectively, three time using GC/MS [19,33]. For IAA quantification, the bacterial culture was centrifuged at 10,000 × g at 4 °C and the supernatant was filtered through a 0.45 µm cellulose acetate filter, acidified to pH 2.8, and 40 µg ml -1 [D5]-IAA was added.…”

Foliar Treatment of Bacillus Methylotrophicus KE2 Reprograms Endogenous Functional Chemicals in Sesame to Improve Plant Health

“…However, the IAA secreting Enterbacter sp. SE992 induced amino acids, sugars and hormonal regulation in cucumber helped to enhance the salt tolerance of plants [29]. Very few studies were reported the PGPR-induced changes on amino acids in crop.…”