Department of Molecular Biotechnology, Graduate School of Advanced Sciences of Matter, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8530, Japan.
Appl Environ Microbiol. 2011 Jun;77(12):4155-62. doi: 10.1128/AEM.02847-10. Epub 2011 Apr 15.
Ralstonia solanacearum is a Gram-negative bacterium and the causative agent of bacterial wilt in many important crops. We treated R. solanacearum with three lytic phages: ϕRSA1, ϕRSB1, and ϕRSL1. Infection with ϕRSA1 and ϕRSB1, either alone or in combination with the other phages, resulted in a rapid decrease in the host bacterial cell density. Cells that were resistant to infection by these phages became evident approximately 30 h after phage addition to the culture. On the other hand, cells infected solely with ϕRSL1 in a batch culture were maintained at a lower cell density (1/3 of control) over a long period. Pretreatment of tomato seedlings with ϕRSL1 drastically limited penetration, growth, and movement of root-inoculated bacterial cells. All ϕRSL1-treated tomato plants showed no symptoms of wilting during the experimental period, whereas all untreated plants had wilted by 18 days postinfection. ϕRSL1 was shown to be relatively stable in soil, especially at higher temperatures (37 to 50°C). Active ϕRSL1 particles were recovered from the roots of treated plants and from soil 4 months postinfection. Based on these observations, we propose an alternative biocontrol method using a unique phage, such as ϕRSL1, instead of a phage cocktail with highly virulent phages. Using this method, ϕRSL1 killed some but not all bacterial cells. The coexistence of bacterial cells and the phage resulted in effective prevention of wilting.
青枯雷尔氏菌是一种革兰氏阴性细菌，也是许多重要作物细菌性萎蔫病的病原体。我们用三种裂解噬菌体处理青枯雷尔氏菌：RSA1 噬菌体、RSB1 噬菌体和 RSL1 噬菌体。单独或组合使用 RSA1 噬菌体和 RSB1 噬菌体感染，会导致宿主细菌细胞密度迅速下降。对这些噬菌体具有抗性的细胞在噬菌体添加到培养物中约 30 小时后变得明显。另一方面，在分批培养中仅被 RSL1 噬菌体感染的细胞在很长一段时间内保持较低的细胞密度（对照的 1/3）。用 RSL1 噬菌体预处理番茄幼苗会严重限制根接种细菌细胞的穿透、生长和运动。在实验期间，所有用 RSL1 噬菌体处理的番茄植物均未出现萎蔫症状，而所有未经处理的植物在感染后 18 天均已萎蔫。RSL1 在土壤中相对稳定，特别是在较高温度（37 至 50°C）下。在感染后 4 个月，从处理过的植物根部和土壤中回收了活性 RSL1 颗粒。基于这些观察结果，我们提出了一种替代的生物防治方法，使用独特的噬菌体（如 RSL1）代替具有高毒性噬菌体的噬菌体鸡尾酒。使用这种方法，RSL1 杀死了一些但不是所有的细菌细胞。细菌细胞和噬菌体的共存导致萎蔫病的有效预防。
