ABSTRACT
Introduction Acquisition of a new gene/trait typically arises from gene duplication and divergence [1]. A classic example of this gradual process is the evolution of a set of pancreatic serine proteases, specically trypsin, chymotrypsin and elastase, from a common precursor [2], [3]. ese paralogs have the same three-dimensional fold and operate by the same enzymatic mechanism, but cleave proteins after dierent amino acids. e opportunities to short-circuit this process and pass a gene between species by horizontal or lateral gene transfer (LGT) would seem extremely limited, and are largely restricted to prokaryotes. In some bacteria there are established routes (conjugation, transduction and transformation) for the exchange of DNA between strains/species, subject to the strictures of the restriction/modication system in the recipient host. LGT becomes particularly evident where the acquisition of the transferred gene confers a selective advantage on the host, as for example in antibiotic resistance [4], [5]. Here, there is the opportunity to acquire a new gene type within one generation rather than by gradual evolution.
