| Ralstonia solanacearum is a worldwide important plant pathogenic bacteria with a wide range of hosts and complex populations.Bacterial wilt caused by Ralstonia solanacearum is one of the most important bacterial diseases in production,especially in tropical and subtropical areas.The prevention and control of crop bacterial wilt has always been a difficult problem in production.So far,it has not been effective in the prevention and control of pesticides.Therefore,it is of great significance to find a new way to prevent and cure bacterial wilt.As a natural killer of bacteria,bacteriophages are highly specific to host bacteria and have been used in food,aquaculture and medical fields.However,they are less used in the prevention and control of bacterial diseases in plants.From the Solanaceae crop root field around the collection soil,using the method of separation of double plate,obtained 15 Ralstonia solanacearum virulent phage infection,through the experiment of 63 Ralstonia solanacearum,all 15 phages are divided into 2categories,revealed a correlation between phage and host bacteria.The results showed that 15of the 63 phage strains of Ralstonia solanacearum diversity analysis,based on 63 strains of Ralstonia solanacearum can be divided into 10 Ralstonia solanacearum phagetypes,of which only 1 phagetype had the same host plants,other phagetypes were isolated from different host plants,showing genetic diversity of Ralstonia solanacearum.Select 6 representative strains of phage biological characteristics was tested,the results show that the optimal multiplicity of infection PPep1501-1,PPep1501-2,PE1507-1-S,phage PE1507-3-S,PTm1555-1 and PTm1555-2-L were 1×10-3、1×100、1×10-2、1×10-3、1×10-2、1×102;the titer was 3.44×108、5.10×108、1.12×109、4.93×108、5.73×108、4.70×108 Pfu/mL;at 3540℃,the range of pH59,phage activity was still high,but in the temperature of 60℃,theactivity was loss.The sensitivity of 6 phages to ultraviolet light,chloroform and ether was different,which affected the formation of Ralstonia solanacearum biofilm and bacterial mobility.The determination of the one step growth curve of bacteriophage PPep1501-1,PE1507-3-S and PTm1555-2-L were 20min,20min and 60min,cracking period was approximately 200 min,200 min and 220min,the outbreak number respectively is 122,69,3,showing the difference of different phage.According to the electron microscopy of phage PTm1555-2-L,the head is twenty faces and has a diameter of about 60nm.It belongs to the tail phage,and the family of long tailed phages.SDS-PAGE electrophoresis showed that there were at least 7 protein bands in phage PTm1555-2-L,and the molecular weight of capsid protein was 44.4KD.Further genome sequencing of phage PTm1555-2-L and sequencing results with virus library database blast,screened 23 scaffolds,a total length of 43344bp,the content of GC is 61.5%,of which 17scaffolds has 7394%homology of Ralstonia solanacearum phage RSK1DNA,Burkholderia phage DC1,Bcep22 or BcepIL02 and other parts of the genome sequence.Gene function prediction results show that the phage genome sequence of PTm1555-2-L gene encoding a total of 42,of which 50%genes encoding for hypothetical protein,Phage protein and other gene encoding Phage-associated homing endonuclease Phage terminase,small subunit,putative transferase,DNA polymeraseIII beta 3’-phosphoadenosine5’-phosphosul fatesulfo Cys H;subunit（EC2.7.7.7）and Phage antirepressor protein,showed that PTm1555-2-L phage there are a lot of gene function remains unclear,PTm1555-2-L is an unknown function and mechanism of the phage,need to be further studied. |
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