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Abstract：
Pseudomonas syringae is a gram-negative plant pathogen that infects plants such as tomato and poses a threat to global crop production. In this study, a novel lytic phage infecting P. syringae pv. tomato DC3000, named phage D6, was isolated and characterized from sediments in a karst cave. The latent period of phage D6 was found to be 60 min, with a burst size of 16 plaque-forming units per cell. Phage D6 was stable at temperatures between 4 and 40 °C but lost infectivity when heated to 70 °C. Its infectivity was unaffected at pH 6-10 but became inactivated at pH ≤ 5 or ≥ 12. The genome of phage D6 is a linear double-stranded DNA of 307,402 bp with a G + C content of 48.43%. There is a codon preference between phage D6 and its host, and the translation of phage D6 gene may not be entirely dependent on the tRNA library provided by the host. A total of 410 open reading frames (ORFs) and 14 tRNAs were predicted in its genome, with 92 ORFs encoding proteins with predicted functions. Phage D6 showed low genomic similarity to known phage genomes in the GenBank and Viral sequence databases. Genomic and phylogenetic analyses revealed that phage D6 is a novel phage. The tomato plants were first injected with phage D6, and subsequently with Pst DC3000, using the foliar spraying and root drenching inoculum approach. Results obtained after 14 days indicated that phage D6 inoculation decreased P. syringae-induced symptoms in tomato leaves and inhibited the pathogen\'s growth in the leaves. The amount of Pst DC3000 was reduced by 150- and 263-fold, respectively. In conclusion, the lytic phage D6 identified in this study belongs to a novel phage within the Caudoviricetes class and has potential for use in biological control of plant diseases.
摘要：
丁香假单胞菌是一种革兰氏阴性植物病原体，感染番茄等植物，对全球作物生产构成威胁。在这项研究中,一种感染丁香假单胞菌的新型裂解性噬菌体。番茄DC3000，称为噬菌体D6，是从喀斯特洞穴的沉积物中分离并表征的。发现噬菌体D6的潜伏期为60分钟，每个细胞的爆发大小为16个斑块形成单位。噬菌体D6在4至40°C之间的温度下是稳定的，但在加热至70°C时失去感染性。其感染性在pH6-10时不受影响，但在pH≤5或≥12时失活。噬菌体D6的基因组为307,402bp的线性双链DNA,G+C含量为48.43%。噬菌体D6及其宿主之间存在密码子偏好，噬菌体D6基因的翻译可能不完全依赖于宿主提供的tRNA文库。在其基因组中总共预测了410个开放阅读框(ORF)和14个tRNA,92个ORF编码具有预测功能的蛋白质。噬菌体D6显示与GenBank和Viral序列数据库中已知的噬菌体基因组的低基因组相似性。基因组和系统发育分析表明，噬菌体D6是一种新型噬菌体。首先使用叶面喷雾和根浸透接种物方法向番茄植物注射噬菌体D6，然后注射PstDC3000。14天后获得的结果表明，接种噬菌体D6减少了番茄叶片中丁香假单胞菌引起的症状，并抑制了病原体在叶片中的生长。PstDC3000的数量减少了150倍和263倍，分别。总之,本研究中鉴定的裂解噬菌体D6属于Cauviricetes类别中的新型噬菌体，具有用于植物病害生物防治的潜力。
