Transduction

In microbiology, transduction is the movement of genes between bacteria inside a bacteriophage. It is one of the three classic routes of horizontal gene transfer, with transformation and conjugation, and it works because phages sometimes package bacterial DNA by mistake. Norton Zinder and Joshua Lederberg discovered it in 1952 in Salmonella, using the phage P22.

There are two classic forms. In generalized transduction, a phage in the lytic cycle chops up the host chromosome and now and then fills a new capsid with a fragment of bacterial DNA instead of its own genome. That particle can inject the fragment into another cell, where it may recombine into the chromosome, so almost any gene can be carried. In specialized transduction, a temperate phage that had integrated into the chromosome as a prophage is cut out imprecisely and takes along host genes lying next to its insertion site, so only those neighbors are transferred. A third mode, lateral transduction, which moves long stretches of DNA, was described in 2018.

Transduction helps bacteria share virulence and resistance genes; phage-borne toxin genes are what make the bacteria behind diphtheria and cholera dangerous. The word has other senses too: signal transduction in cell biology, and gene delivery by a viral vector in gene therapy.