Effects Of Plant Root Exudates On The Biological Activity Of Bacillus Velesi S3-1

In recent years,people have used biocontrol bacteria that have been screened from nature to reduce the number of pathogens and to suppress their pathogenicity.This not only effectively controls crop diseases and avoids huge economic losses,but also affects humans,animals and plants.There is no harm in the environment,environment and energy,which has promoted the sustainable development of agriculture and has become a research hotspot in the prevention and control of plant diseases.Recently,our laboratory has isolated a highly active Bacillus velezensis strain S3-1,which has a strong ability to inhibit disease.In order to apply it on a larger scale to real life,the main task of the thesis is to study the colonization of S3-1in soil and the effects of root exudates on S3-1 activity.In this study,S3-1 was found to potently colonize the roots of maize through pot experiments.At 0,3,6 and 9 cm from the horizontal distances of lateral roots of maize,the number of colonization gradually decreased.And at 0,3,6 and 9 cm from the vertical distances of main roots of maize,the number of colonization showed a trend of first increase and then decrease,and the number of S3-1 was significantly less than that of the control group at a distance of 9 cm from the root,which was almost the same as that of the field experiments.We speculate that certain components secreted by the root system of maize attract colonization of S3-1.To further explore the effects of root exudates on the biological activity of strain S3-1,such as chemotaxis,swarming motility and biofilm formation,we collected exudates from the roots of maize seedlings and found that the exudates had obvious chemotaxis,swarming motility,and the ability to form biofilms,increased 1.4 times,1.6 times and 4.1 times compared with the control,respectively.And analysis from the genome showed that S3-1 had a total of 54 genes related to exercise and 37biofilm-related genes.The organic acids(citric acid,malic acid,and oxalic acid),amino acids(glycine,valine,and phenylalanine),and sugars(glucose,fructose,and sucrose)were representative of the root exudates.The results show that the single and mixed components of the three major classes of substances all have significant chemotaxis,swarming motility,the ability to form biofilms,and the ability to induce S3-1 to be recruited to the corn roots.Among them,the mixed component of malic acid,phenylalanine and glucose has the strongest ability of chemotaxis and swarming motility.The combination of oxalate,proline and glucose induced the strongest ability of S3-1 to form biofilm.The mixed component of malic acid,phenylalanine and glucose induced the strongest ability of S3-1 to be recruited in maize roots,which was consistent with the results of chemotaxis experiments and swarming motility assay.This may be due to the ability of chemotaxis and swarming motility were stronger than the ability of biofilm formation in the colonization mechanism.This provides an important foundation for studying the biological control mechanism of the microenvironment of the roots.