| Summary: | Organic farming is gaining importance and acceptance worldwide due to its beneficial effects in agriculture and standing against losses caused by chemical fertilizers, pesticides and fungicides. Plant growth promoting bacteria (PGPB) plays an important role in organic farming by fixing atmospheric nitrogen, chelate iron, solubilizing phosphorous, producing and modulating phytohormones, providing antibiotics against pathogens. Understanding interaction mechanisms between PGPB and plant will be helpful in developing new formulations to form a strong symbiotic relationship between plant and bacteria. Bacillus amyloliquefaciens UCMB5113 is a red pigmented, rod shaped Gram positive bacteria which has been isolated from fields of the Ukraine. In the present study UCMB5113 and its interactions with the plant has been characterized. There was a significant promotion of plant root growth and protection against biotic stress with the application of 10 μl of 1x107/ml CFU UCMB5113 culture in Arabidopsis. The UCMB5113 can significantly withstand plant antimicrobial activity to stimulate plant root growth, but needs root hair defective RHD proteins to stimulate root hair elongation. UCMB5113 has significantly inhibited primary root elongation and developed number of lateral roots and root hairs in ethylene over expressed mutant, which suggests that it may be affecting ethylene signaling pathway in plants. UCMB5113 has a distinct red pigmentation which is a 38.5kDa water soluble protein with maximum absorbance at 422nm. These features are similar to the Orange Carotenoid Protein (OCP) of Synechocystis PCC 6803. This red pigmented protein has no significant effect on plant root growth promotion. Further biochemical and molecular studies are required to characterize and confirm the mechanisms of interaction.
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