Gene transfer in the marine environment

This review summarises the literature on bacterial gene transfer in marine ecosystems. Relevant experiments carried out in model systems are also included. Prerequisites for the main gene transfer mechanisms, transformation, transduction and conjugation are discussed, such as concentrations of extracellular DNA in marine waters, numbers of bacteriophages in sea water and frequency of plasmids in marine bacteria. Transfer of chromosomal genes as well as plasmids are considered. We also discuss the possibility that gene transfer is more frequent in surface-associated bacterial communities. Examples of relevant studies using various solid surfaces and from the air-water interface are summarized. We suggest that there is a higher ‘flow-rate’ of genetic information through surface-associated communities compared to bulk water communities.