The proposed research will investigate the two different mechanisms by which organisms acquire new capabilities: 1) mutation, changes in existing genes, and 2) recombination, the acquisition of genes from different organisms. Both mechanisms occur in nature but information is lacking about the relative likelihood of the different events and the different consequences of each type of event. These questions will be addressed using an experimental system of bacteriophage (viruses that infect bacteria) and their bacterial hosts. New viral strains with the ability to infect previously resistant hosts will be produced in the laboratory via each mechanism, and molecular techniques will be used to identify the genes responsible for the changes in host range. The study will compare the activity of the new strains produced by recombination and mutation, to determine if host range changes caused by recombination might be more effective than those caused by mutation. Finally, the new viruses will be grown in the laboratory for several generations to determine how the initial changes allowing the infection of a new host drive the acquisition of further modifications.
Acquisition of new functions by organisms, especially microorganisms, is becoming an increasingly important issue for human health and safety. HIV, the virus that causes AIDS, is rapidly mutating to produce forms resistant to current drug therapy. New influenza strains appear each year, and major changes such as those that caused the 1914 pandemic are thought to result from recombination. The proposed research will increase our general understanding of the mechanisms and outcomes of these different processes. In addition, the experimental viral system will allow the collection of data specific to the study of the origin of viruses capable of infecting new hosts.
