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Zusammenfassung:
Integrative and conjugative elements (ICEs) are self-transmissible mobile elements that transfer functional genetic units across broad phylogenetic distances. Accessory genes shuttled by ICEs can make significant contributions to bacterial fitness, yet ICEs that carry accessory genes encoding functions other than antimicrobial resistance remain poorly characterized. Recent observation of the rapid acquisition of ICEs in a pandemic lineage of Pseudomonas syringae led to investigation of the structural and functional diversity of these elements. Fifty-three unique ICE types were identified across the species complex. ICEs display distinct evolutionary histories, are highly recombinogenic, exhibit a conserved structure and are punctuated by hotspots of accessory gene integration. Many ICEs carry a 16 kb transposon-like entity (Tn6212) that enhances bacterial fitness on TCA-cycle sugars. RNA-seq performed on a set of nested Tn6212 mutants show striking succinate-dependent genome-wide manipulation of gene expression with the majority of effects attributable to a single LysR regulator. The selective advantage underpinning recent global dissemination of Tn6212 arises from capacity to manipulate bacterial metabolism in response to TCA- cycle sugars resulting in redistribution of cellular resources in order to maximize growth rate.
