Abstract: Bacillus amyloliqueliciens FZB42 is a plant growth-promoting rhizobacteria (PGPR) that promotes plant growth, improves disease resistance, drought and salt tolerance abilities. However, there are few reports on the growth, biofilm formation, root colonization ability and exoposaccharides production of B. amyloliquefaciens FZB42 under drought stress. In this study, PEG-6000 was used to simulate drought stress, and the osmotic potentials were -0.05, -0.50, -1.48 and -2.95 MPa, respectively. The growth, biofilm formation, rhizosphere colonization ability and extracellular polysaccharide yield of B. amyloliquefaciens FZB42 under different concentrations of PEG-6000 were determined. This paper provided a theoretical basis for improving the drought resistance of plants by B. amyloliquefaciens FZB42. The results showed that: (1) High concentration of PEG-6000 can significantly inhibit the growth, biofilm formation and colonization ability of B. amyloliquefaciens FZB42 in Arabidopsis rhizosphere. When 15% PEG-6000 was added, the OD₆₀₀ and numbers in the rhizosphere reached the lowest values of 1.542 and 1 500 cfu·mm^-1, respectively. (2) The production of exoposaccharides of B. amyloliquefaciens FZB42 increased significantly with the increasement of PEG-6000 concentration. When there was none PEG-6000, the extracellular polysaccharide content was the lowest at 150.2 mg·L^-1. When 15% PEG-6000 was added, the yield of extracellular polysaccharide was the highest at 568.8 mg·L^-1.

Key words: drought stress, Bacillus amyloliquefaciens FZB42, biofilm, root colonaization, exoposaccharides