Starter Grant: Evolution of Host Range in the Bacteriophage PhiX174

伯奇博士将使用噬菌体phiX 174和它的替代宿主E. coli和革兰氏阳性菌S.鼠伤寒沙门氏菌，以研究宿主限制对该病毒宿主范围进化的影响。 通过操纵宿主限制，她将检验以下假设：当宿主有限时，宿主范围扩展的收益大于成本;当宿主丰富时，宿主范围扩展的成本大于收益。 寄生虫宿主范围扩大的优点包括减少对宿主的竞争，减少寻找宿主所花费的时间，以及增加传播到合适宿主的可能性。 然而，寄生虫最常被观察到专化于有限数量的宿主。 这种专门化可以用与广泛的宿主范围相关的各种成本来解释，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的可能的权衡。 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。 相比之下，伯奇博士将通过向噬菌体phiX 174展示扩大宿主范围的益处不同的生态条件来研究宿主范围的演变。 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转移到人类中一样。

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.