this arena that gene transfer is experiencing a revival in
interest. The sequencing of entire microbial genomes
(Fleischman et al., 1995; Frazer et al., 1995; Bult et al.,
1996) has shown that microbes are mosaics of acquired
genes. In fact, the rooting of the universal tree is highly
problematic because of multiple transfer events between
the kingdoms.
In this review I have focused on gene transfer to
indigenous organisms in the environment, paying less
attention to laboratory and microcosm studies. Because
much work has been done on conjugation and less on
transduction, I emphasize some of the more startling
findings coming from the latter field. Finally, how gene
transfer has impacted our understanding of molecular
phylogeny will be examined.