Biofilm Phenotype Of Bacillus Amyloliquefaciens PEBA20 And Its Correlation With Antimicrobe Activity

Researches on bacteria with bio-control acticity has become a hot topic about the biological control, but it's application was confined due to the unstable of the antibacterial activity .This can be attributable to the difference environment between laboratory culture and natural conditions to a great degree. There are also Increasing evidence demonstrate that, in natural habitats, most microbes exist as biofilm rather than as plankton. Most time of the microbial life is under the condition of biofilm.Based on the above two points, this experiment is about the relationship between the biofilm phenotype and antibacterial activities of a single Bacillus amyloliquefaciens bacterial strain PEBA20 which is isolated from poplar.At first, we elaborated the biofilm phenotype of PEBA20-W0314 systematically. When cultivated on NA solid medium for 5 days, the biofilm phenotype of PEBA20-W0314 liked the"Bird's Nest". They didn't expand to a large space, heaved skyward obviously and were sub-orbicular. When cultivated in NB liquid medium for 2 days statically, the biofilm phenotype of PEBA20-W0314 was compact, strong, integrity and had wave-like pattern on the surface.The result of artificial subculture showed that the whole process could be separated by F9. The biofilm phenotype and antibacterial activity changed slowly during the early stage. But obvious changes appeared during the later stage. By the time of F9, the antibacterial activity of PEBA20 against Bipolaris maydis,Valsa mali,Botryosphaeria dothidea and Rizoctonia cerealis descended 9.1%,13.2%,5.4% and 2.4% respectively. Also, the change of biofilm phenotype became obviously after F9. The diversity of single colonies was notable but this feature turned into inconspicuous during the later stage. There are 8 kinds of single colonies before F9, but developed into 2 kinds which had distinct feathers from each other. Meanwhile, the thickness and sturdiness descended gradually. The above results showed that the biofilm phenotype and antibacterial activity of the wild biocontrol bacteria W0314 changed synchronously during subculture in laboratory, the law of there change had relevance. The detections about antibacterial activity against B. dothidea of PEBA20 with different biofilm phenotype was carried on both petri dish and poplar callus.We compared the biofilm phenotype and antibacterial activity of W0314 and NM0705. The results showed that, compared with W0314, NM0705 had smoother but larger single colonies. The biofilm formed on the liquid gas interface was thinner and fertilizer. Half quantitative method detection showed that the amount of bacteria individuals of NM0705 was about the one half of W0314. Meanwhile, the antibacterial activity of NM0705 also descended. The inhibition rates of hypha growth against the four plantpathogenicfungi declined by 89.3%,56.9%,38.5% and 92.3% respectively. The result of nucleotide sequence analysis of 16SrRNA and tasA from NM0705 which root in our laboratory by repeatedly subculture shows that the sequence similarity between W0314 and NM0705 is 99%. The above results formed the foundation for more reach on biofilm feature by PEBA20. The result also given evidence about same strain presented different biofilm phenotype.