Colonization Of Paenibacillus Polymyxa In The Phyllosphere Of Camellia Sinensis And Its Effect On The Bacterial Community

Paenibacillus polymyxa is a plant growth-promoting bacterium which can act as both microbial pesticide and fertilizer in agriculture.It has been extensively studied as microbial fertilizer on rhizosphere,while the study on phyllosphere is very little.The phyllosphere represents an active suface on which complex interactions occur among the plants,the microorganisms and the environment.The plants provide the microorganinsms the supportive sites and the microorganisms conversely produce beneficial or harmful effect on the plants.While colonization is the prerequisite during this process.In this study,the bacteria P.polymyxa EBL06 was cultured using the sweet potato starch wastewater(SPSW)and then sprayed on the leaves of Camellia sinensis,which was desiged to explore the colonization of P.polymyxa and its effect on the pholloshere bacterial community.Real-time fluorescent quantitative PCR technology was adopted to trace the colonization of P.polymyxa,as well as the abundance of the total bacteria,total fungi and the pathogens.While the phyllosphere bacterial community was evaluated by the high-throughput sequencing technology.The results are as follows:1)P.polymyxa EBL06 was cultured and sprayed on the leaves of Camellia sinensis in spring and autume,separately.It can be observed that P.polymyxa could colonize on the phollosphere successfully and survive for 21 days in spring and more then 89 days in autumn.2)The human bacterial pathogens of Pseudomonas aeruginosa,Bacillus cereus,Mycobacterium spp.were detected by qPCR during the process of P.polymyxa colonization.The results showed that there was no obvious effct of P.polymyxa injection on the pathogens.3)The bacteria 16S rRNA genes were detected by the high-throughput sequencing technology,which showed that on the level of phyla,the most dominant bacteria on the phollosphere of Camellia sinensis were Proteobacteria,Bacteroidetes and Actinobacteria.While,on the level of genus,the most dominant bacteria were season dependent,unclassified,Methylobacterium,Chryseobacterium and Sphingomonas in spring,and Methylobacterium,Sphingomonas,Aureimonas and Pantoea in autumn.4)The injection of P.polymyxa could increase the abundance of certain bacteria,such as Firmicutes and Chloroflexi.However,it was decreased to control level three days later.5)The analysis based on the high-throughput sequencing showed that seasonal variation took more important role on the Camellia sinensis phyllosphere bacterial community than P.polymyxa injection,and the diversity of the bacteria was much higher in spring than in autumn.