Starter Grant: Evolution of Host Range in the Bacteriophage PhiX174

伯奇博士将使用噬菌体phiX174及其替代宿主大肠杆菌和鼠伤寒沙门氏菌来研究宿主限制对该病毒宿主范围进化的影响。通过操纵主机限制，她将测试这样的假设，即主机范围扩展的好处大于主机有限时的成本，以及主机丰富时主机范围扩展的成本大于好处。针对寄生虫扩大宿主范围的优势包括减少对宿主的竞争，减少搜索宿主所花费的时间，以及增加传播到合适的宿主的可能性。然而，寄生虫最常被观察到专门针对有限数量的宿主。这种专业化可以用与广泛的宿主范围相关联的各种成本来解释，包括在一个宿主上的适应性和在替代宿主上的适应性之间可能的权衡。对寄主范围的实验研究往往集中在扩大寄主范围的潜在成本上，而不是潜在的好处上。相反，伯奇博士将通过向噬菌体phiX174呈现不同于扩大宿主范围的益处的生态条件来研究宿主范围的进化。这种性质的研究可能有助于确定有利于获得新宿主的生态条件，就像最近艾滋病毒从黑猩猩进入人类体内一样。

Dr. Burch will use the bacteriophage phiX174 and its alternative hosts, E. coli and S. typhimurium, to investigate the impact of host limitation on the evolution of host range in this virus. By manipulating host limitation, she will test the hypothesis that the benefits of host range expansion outweigh the costs when hosts are limited, and that the costs of host range expansion outweigh the benefits when hosts are abundant. The advantages of host range expansion for parasites include reduced competition for hosts, reduced time spent searching for hosts, and increased probability of transmission to a suitable host. However, parasites are most often observed to specialize on a limited number of hosts. This specialization may be explained by a variety of costs associated with broad host range, including a possible trade-off between fitness on one host and fitness on alternative hosts. Experimental studies of host range have tended to concentrate on the potential costs of expanded host range rather than the potential benefits. In contrast, Dr. Burch will study the evolution of host range by presenting the bacteriophage phiX174 with ecological conditions in which the benefits of expanded host range differ. Studies of this nature may help identify ecological conditions that favor acquisition of new hosts, as in the recent movement of HIV into humans from chimpanzees.