Conjugative elements: Host chromosome function modifiers

Abstract

Conjugative transfer of plasmids and integrative and conjugative elements (ICE ICE s) play a key role in rapid bacterial evolution and adaptation. These elements give a host several new phenotypes that can be advantageous for host survival in some cases, but disadvantageous in others. Comparisons of growth rate and biomass yield as well as competition assays have shown that carriage of plasmids frequently imposes a fitness cost on the host cells. New phenotypes are caused by cross talk between plasmid- and chromosome-encoded factors during implantation of regulatory circuits into the host native transcriptional network. Nucleoid-associated proteins (NAPs NAPs) are important factors for adaptation of the ICEs to the new host cell environment. Plasmids and ICEs, containing genes involved in the biodegradation of various compounds, are excellent models to study the impact on the host. A chlorocatechol-degradative ICE, ICE clc ICE clc, can express its degradative genes without changing the fitness of the new host. The host of toluene/xylene-degradative plasmid pWW0 pWW0 builds cooperative regulatory systems to express metabolic activity. The influence of naphthalene-degradative plasmid NAH7 NAH7 on the host cells is modest, and the carriage of NAH7 alleviates host stress when exposed to naphthalene. The effects of carbazole-degradative pCAR1 pCAR1 carriage on the host cells depend on the type of host, and the NAPs encoded on pCAR1 are important for controlling the transcriptional network of the host. The extent of the impact on the host cells changes the genetic stability of these elements in the host, which is important for spreading these genetic elements among different bacteria.