Bacillus mycoides: novel tools for studying the mechanisms of its interaction with plants

Plant growth promoting rhizobacteria (PGPR) is a group of bacteria that colonize the plant roots and promote plant growth. Understanding of the molecular mechanisms of how plants and PGPR co-exist and benefit each other can provide new strategies to improve plant health and productivity. Bacillus mycoides is a gram-positive bacterium that is abundantly present in healthy potato roots and has strong plant growth promoting potential. In this research we investigated the molecular mechanism of B. mycoides-plant interactions. To this end, a multidisciplinary approach was employed and novel molecular genetic tools were developed. The comparative genomics revealed that there is a putative endophytic clade within the B. mycoides species. The optimized GFP and RFP were used to label an endophytic and a soil strain, respectively. Their root colonization patterns were observed by confocal laser scanning microscope, which showed that the endophytic strain has better root colonization ability than the soil strain. The transcriptome analysis showed that the endophytic strain can utilize a broader range of substrates in the rhizosphere niche than the soil strain. It was discovered that siderophores produced by B. mycoides aid the growth of iron-starved plants and play an important role in the B. mycoides-plant interaction.