The Antibacterial Property Analysis Of Bacillus BU108 And Biocontrol Of Potato Scab

In recent years,potato scab presented serious trend in China.The long-term use of chemical pesticides not only caused harm to the environment and man,but also broke the balance of rhizosphere,leading to more serious scab.To solve the above problems,In this study,a strain of biocontrol against scab was isolated and identified,which had significantly inhibitory effect on scab.Its active protein was separated and identified.Then,the culture condition of this strain was optimized,and the biocontrol effect was tested through pot and field trail.The detailed process was described below.Soil was collected from potato scab disease filed,and antagonistic strain was isolated by plate dilution method.The strain showed a significantly inhibitory effect on scab,which was identified as Bacillus by 16 S r DNA alignment,and named BU108.The crude protein was extracted by ammonium sulfate precipitation and determined to have antibacterial activity.The stability analysis showed that crude protein lost its activity when heated at 100°C for 5 min,and could be inactivted by 0.5 mg/m L of pepsin or trypsin treatment.The optimal p H was 7.The crude protein was insensitive to organic solvent and metal ions,but Tween-80.The active protein was further purified by anion exchange column.Three protein bands were isolated and sequenced by mass spectrometry,and all of them were degradation fragments of Gamma glutamyl transpeptidase(GGT).The recombinant expressed proteins of GGT didn't show antibacterial effect,while the predicted antimicrobial peptides of GGT had certain antibacterial activity.It could be inferred that the degradation products of GGT in the culture process could inhibit scab.The single factor assay and multi-level test were used to optimize the antibacterial activity of BU108.C/N,Na Cl content and culture time were confirmed by PB experiment as the three main influencing factors.Then,response surface analysis was used to determine that 1/2.5 of C/N,0.75% of Na Cl and incubation for 23 h was the best culture conditions.The pot experiment was tested,pathogenic bacteria,BU108(low concentration)and BU108(high concentration).The results showed that BU108(high concentration)had the best effect with inhibition rate at 90.00%,which reached a significantly difference.The field experiments were carried.The treatment was same with the pot trail.The result showed that BU108(high concentrations)gained an inhibition rate at 88.57%,which also reached a significantly difference.Plant and field experiments showed that the BU108 could effectively inhibit the occurence of scab.In this study,a significant biocontrol strain BU108 was isolated.The stability of the antibacterial substance of the strain was analyzed.Its protein components were tested to have antibacterial activity.The further analyses found that the fragment of GGT had antibacterial activity.The culture condition of BU108 was optimized to gain the best antibacterial activity.The BU108 against potato scab were executed by Pot and field experiment and got a satisfied result.This study can not only provid the material for the biological control of potato scab,but also accumulate experience for the practical application of BU108.