University of Pittsburgh
March 4, 1999


Contact:  412-624-4147

PITTSBURGH, March 2 -- Researchers at the University of Pittsburgh have gained new insights about the evolution of bacteriophages, the viruses that infect bacteria. Their surprising discovery is that virtually all bacteriophages (phages) are members of one large, interrelated family. These results are to be published today in the Proceedings of the National Academy of Sciences.

Roger Hendrix and Graham Hatfull, professors in the Department of Biological Sciences at Pitt, working in collaboration with Maggie Smith at the University of Nottingham, U.K., arrived at these conclusions through detailed analysis and comparison of the genomes of selected bacteriophages. (A phage's "genome" is its entire collection of genes.)

The findings were unexpected since many of the phage genomes do not appear related by the normal criteria of similarities in their DNA or protein sequences. The relatedness of these phages therefore had to be inferred from pairwise comparisons of several phages and phage-remnants found within bacterial chromosomes. This comparative genomic approach provides a compelling view of the overall global population of phages.

"Nature is extremely prolific at generating new types of viruses," Hendrix commented. "There are more bacteriophages than all the other organisms in the biosphere put together, and remarkably, our results show that this whole mass of viruses is involved in an ongoing orgy of gene swapping on a global scale."

"It's a really efficient mechanism for generating new combinations of genes and therefore new varieties of viruses," added Hatfull.

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