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Endophytic bacteria have already been studied for their beneficial support to plants to manage both biotic and abiotic stress through an array of well-established mechanisms. They have either direct or indirect impact on mobilizing diverse nutrients and elements from soil to plants. However, detailed insight into the fine-tuning of plant elemental composition by associated microorganism is very limited. In this study, endophytic Bacillus Fcl1 characterized from the rhizome of Curcuma longa was found to have broad range of plant growth-promoting and biocontrol mechanisms. The organism was found to have indole acetic acid and 1-aminocyclopropane-1-carboxylate deaminase production properties along with nitrogen fixation. The Bacillus Fcl1 could also inhibit diverse phytopathogens as confirmed by dual culture and well diffusion. By LC-MS/MS analysis, chemical basis of its antifungal activity has been proved to be due to the production of iturin A and a blend of surfactin compounds. Moreover, the organism was found to induce both plant growth and disease resistance in vivo in model plant system. Because of these experimentally demonstrated multiple plant probiotic features, Bacillus Fcl1 was selected as a candidate organism to study its role in modulation of plant elemental composition. ICP-MS analysis of Bacillus Fcl1-treated plants provided insight into relation of bacterial interaction with elemental composition of plants.

Alcaligenes sp. d(2) isolated from soil was earlier reported as a potent phenol-degrading organism. In the Fourier transform/infrared spectroscopic analysis of the biodegraded sample, the aromatic stretching was missing and the spectrum gave evidence for the presence of polyhydroxybutyric acid along with its depolymerized products. In the gas chromatogram of the biodegraded sample, the peak of phenol at 14.997 min was absent and there were many peaks after 20 min. The organism could carry out 100% degradation of phenol in 32 h and could progressively result in early accumulation of polyhydroxybutyrate (PHB) intracellularly from 8 h onwards. The various conditions optimized for the maximum accumulation of intracellular PHB were pH 7.0, incubation time 24 h, phenol concentration 15 mg/100 ml, and ammonium sulfate concentration 25 mg/100 ml.

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Endophytic bacteria with multi-trait plant probiotic features have been demonstrated to have applications to enhance agricultural productivity by supporting the plant growth, yield and disease resistance under harsh environmental conditions. The xerophytic plant Ananas comosus was selected as the source for endophytic bacterial isolation in the current study. This has resulted in the identification of organisms with antifungal and plant growth promoting properties. Interestingly, endophytic bacteria with antifungal activity were found to have drought tolerance property also. These organisms were demonstrated to express the plant beneficial mechanisms like IAA, ACC deaminase and nitrogen fixation under drought condition. The selected organisms were further identified as Bacillus sp. (Acb9), Providencia sp. (Acb11), Staphylococcus sp. (Acb12), Staphylococcus sp. (Acb13) and Staphylococcus sp. (Acb14)(Acb 14). In addition, LC-MS/MS analysis of extract from Acb 9 has resulted in the identification of surfactin with m/z of 994. Priming of selected endophytes with Vigna radiata seedlings also showed enhanced growth parameters such as shoot length, root length and root numbers when compared to the control. The shoot length of Acb 9 treatment was found to be 18.833 ± 0.687 cm, where the control value for same was 13.976 ± 0.585 cm and the root length was 3.9 ± 0.99 when compared to control (1.54 ± 0.628). The root length was 3.9±0.99 which was also higher than control (1.54±0.62).The results of the study indicate the promise of endophytic bacteria for field application under changing agro-climatic conditions.