uncovering the prevalence and diversity of integrating conjugative elements in actinobacteria发现的普遍性和多样性结合共轭元素放线菌.pdf

Uncovering the Prevalence and Diversity of Integrating Conjugative Elements in Actinobacteria . . ´ Mariana Gabriela Ghinet , Eric Bordeleau , Julie Beaudin, Ryszard Brzezinski, Sebastien Roy*, Vincent Burrus* ´ ´ ´ ´ ´ Centre d’etude et de valorisation de la diversite microbienne, Departement de biologie, Universite de Sherbrooke, Sherbrooke, Quebec, Canada Abstract Horizontal gene transfer greatly facilitates rapid genetic adaptation of bacteria to shifts in environmental conditions and colonization of new niches by allowing one-step acquisition of novel functions. Conjugation is a major mechanism of horizontal gene transfer mediated by conjugative plasmids and integrating conjugative elements (ICEs). While in most bacterial conjugative systems DNA translocation requires the assembly of a complex type IV secretion system (T4SS), in Actinobacteria a single DNA FtsK/SpoIIIE-like translocation protein is required. To date, the role and diversity of ICEs in Actinobacteria have received little attention. Putative ICEs were searched for in 275 genomes of Actinobacteria using HMM- profiles of proteins involved in ICE maintenance and transfer. These exhaustive analyses revealed 144 putative FtsK/SpoIIIE- type ICEs and 17 putative T4SS-type ICEs. Grouping of the ICEs based on the phylogenetic analyses of maintenance and transfer proteins revealed extensive exchanges between different sub-families of ICEs. 17 ICEs were found in Actinobacteria from the genus Frankia, globally important nitrogen-fixing microorganisms that establish root nodul