INSTITUTO DE INVESTIGACIONES EN MICROBIOLOGIA Y PARASITOLOGIA MEDICA
Unidad Ejecutora - UE
capítulos de libros
Distribution of genes in bacterial communities
MARCELO CASSINI Y DANIELA CENTRON
Lugar: Oxford; Año: 2013; p. 189 - 199
In bacteria, reproduction is not linked to sexuality, as occurs in eukaryotes. Bacteria divide by binary fission, which generates individual clones. However, there are parasexual processes of lateral genetic transfer that, coupled with mutations, generate variability in populations. This mechanism of gene exchange takes place independently of reproduction. It is a driving force in the adaptation to novel niches and the evolution of genomes based on the mobilisation of DNA among different strains, genera and even phyla (Touchon 2010). With the availability of these mechanisms, it is likely that any piece of DNA from a bacterial source may be subjected to processes involving lateral genetic transfer. Furthermore, bacteria are exposed to a constant provision of DNA most of the time, from which they can acquire large blocks that can generate remarkable quantities of biodiversity, which may in turn be adaptive under selection pressure. The mechanisms that allow this exchange of information at a DNA level are: transformation, conjugation and transduction. The process of transformation is the genetic alteration of a bacterial cell resulting from the uptake and expression of foreign DNA or RNA. Transduction occurs when the bacterial DNA is moved from one bacterium to another by a virus (or bacteriophage). Finally, conjugation is a process in which a bacterial cell transfers genetic material to another cell by cell-to-cell contact. Despite the intense gene flow in the eubacterial world, microbial biogeography analyses suggest that genetic population structure in the environment is non-random, implying that there are ecological processes that are responsible at least in part for this spatial variation (Martiny et al. 2006).