Caister Academic Press

What Maintains Plasmids Among Bacteria?

Francisco Dionisio, Teresa Nogueira, Luís M. Carvalho, Helena Mendes-Soares, Sílvia C. M. Mendonça, Iolanda Domingues, Bernardino Moreira and Ana M. Reis
from: Horizontal Gene Transfer in Microorganisms (Edited by: M. Pilar Francino). Caister Academic Press, U.K. (2012)


The ubiquity of plasmids in nature contrasts with our ability to understand their maintenance. Despite the ability of plasmids to transfer across different bacterial taxonomic groups and to carry useful genes to bacterial cells, it is unclear which factors are responsible for plasmid maintenance among bacterial populations. In this review, we present several hypotheses aiming at explaining plasmid existence: efficiency of self-transfer, advantageous genes, transitory derepression of conjugative pili synthesis, compensatory mutations, the existence of amplifier strains, positive epistasis between chromosomal mutations and plasmids, selective sweeps, frequent cross-species transfer, as well as three types of social interactions (exploitation avoidance in the production of public goods, pathogen- or parasite-mediated harmful behavior, biofilm formation). These hypotheses imply that plasmids and their hosts are adaptable to variable conditions and even that plasmids can be irreplaceable under particular circumstances read more ...
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