Data from: Frequency and fitness consequences of bacteriophage φ6 host range mutations

Viruses readily mutate and gain the ability to infect novel hosts, but few data are available regarding the number of possible host range-expanding mutations allowing infection of any given novel host, and the fitness consequences of these mutations on original and novel hosts. To gain insight into the process of host range expansion, we isolated and sequenced 69 independent mutants of the dsRNA bacteriophage Φ6 able to infect the novel host, Pseudomonas pseudoalcaligenes. In total, we found at least 17 unique suites of mutations among these 69 mutants. We assayed fitness for 13 of 17 mutant genotypes on P. pseudoalcaligenes and the standard laboratory host, P. phaseolicola. Mutants exhibited significantly lower fitnesses on P. pseudoalcaligenes compared to P. phaseolicola. Furthermore, 12 of the 13 assayed mutants showed reduced fitness on P. phaseolicola compared to wildtype Φ6, confirming the prevalence of antagonistic pleiotropy during host range expansion. Further experiments revealed that the mechanistic basis of these fitness differences was likely variation in host attachment ability. In addition, using computational protein modeling, we show that host-range expanding mutations occurred in hotspots on the surface of the phage's host attachment protein opposite a putative hydrophobic anchoring domain.病毒易于发生突变并获得感染新型宿主的能力，但目前针对可感染任意特定新型宿主的宿主范围扩张突变的数量，以及这些突变在原始宿主与新型宿主中的适合度效应，相关数据仍较为匮乏。为解析宿主范围扩张的过程，我们分离并测序了69株能够感染新型宿主类产碱假单胞菌（Pseudomonas pseudoalcaligenes）的双链RNA（double-stranded RNA，dsRNA）噬菌体Φ6独立突变株。总计在这69株突变株中，我们鉴定出至少17种独特的突变组合类型。我们针对17种突变基因型中的13种，分别在类产碱假单胞菌与标准实验宿主嗜菜豆假单胞菌（Pseudomonas phaseolicola）中开展了适合度测定。相较于嗜菜豆假单胞菌，各突变株在类产碱假单胞菌中的适合度显著更低。此外，13株被测突变株中有12株在嗜菜豆假单胞菌中的适合度相较于野生型Φ6有所下降，这证实了宿主范围扩张过程中拮抗多效性（antagonistic pleiotropy）的普遍存在。后续实验表明，这类适合度差异的分子机制可能与宿主吸附能力的变化有关。此外，通过计算蛋白质建模，我们发现宿主范围扩张突变集中发生在噬菌体宿主吸附蛋白表面与推定疏水锚定结构域相对的突变热点区域。