Daniel Castillo, Johanna Jørgensen, Krister Sundell, Lone Madsen, Inger Dalsgaard, Tom Wiklund, Mathias Middelboe
Marine Biological Section, Department of Biology, University of Copenhagen, Helsingør, Denmark.
Instituto de Investigación Interdisciplinar en Ciencias Biomédicas SEK (I3CBSEK), Universidad SEK, Santiago, Chile.
Environ Microbiol. 2021 Aug;23(8):4185-4199. doi: 10.1111/1462-2920.15593. Epub 2021 May 25.
The fish pathogen Flavobacterium psychrophilum infects farmed salmonids worldwide, and application of bacteriophages has been suggested for controlling disease outbreaks in aquaculture. Successful application of phages requires detailed knowledge about the variability in phage susceptibility of the host communities. In this study, we analysed the genetic diversity of F. psychrophilum hosts and phages from the Baltic Sea area to identify genetic determinants of phage-host interaction patterns. A host range analysis of 103 phages tested against 177 F. psychrophilum strains (18 231 phage-host interactions) identified nine phage clusters, infecting from 10% to 91% of the strain collection. The core genome-based comparison of 35 F. psychrophilum isolates revealed an extremely low overall genomic diversity (>99.5% similarity). However, a small subset of 16 ORFs, including genes involved in the type IX secretion system (T9SS), gliding motility and hypothetical cell-surface related proteins, exhibited a highly elevated genetic diversity. These specific genetic variations were linked to variability in phage infection patterns obtained from experimental studies, indicating that these genes are key determinants of phage susceptibility. These findings provide novel insights on the molecular mechanisms determining phage susceptibility in F. psychrophilum and emphasizes the importance of phages as drivers of core genomic diversity in this pathogen.
鱼类病原菌嗜冷黄杆菌感染全球范围内养殖的鲑科鱼类，有人建议应用噬菌体来控制水产养殖中的疾病暴发。噬菌体的成功应用需要详细了解宿主群体中噬菌体敏感性的变异性。在本研究中，我们分析了来自波罗的海地区的嗜冷黄杆菌宿主和噬菌体的遗传多样性，以确定噬菌体-宿主相互作用模式的遗传决定因素。对103种噬菌体针对177株嗜冷黄杆菌菌株进行的宿主范围分析（18231次噬菌体-宿主相互作用）确定了9个噬菌体簇，感染了10%至91%的菌株集合。对35株嗜冷黄杆菌分离株进行的基于核心基因组的比较显示，总体基因组多样性极低（相似度>99.5%）。然而，一小部分16个开放阅读框，包括参与IX型分泌系统（T9SS）、滑行运动和假定的细胞表面相关蛋白的基因，表现出高度升高的遗传多样性。这些特定的遗传变异与实验研究中获得的噬菌体感染模式的变异性相关，表明这些基因是噬菌体敏感性的关键决定因素。这些发现为决定嗜冷黄杆菌噬菌体敏感性的分子机制提供了新的见解，并强调了噬菌体作为该病原菌核心基因组多样性驱动因素的重要性。
