The Role of Integrative and Conjugative Elements in Antibiotic Resistance Evolution

Integrative and conjugative elements (ICEs) and plasmids can both promote the spread of antibiotic resistance (AR), but they vary in important characteristics, including transmission dynamics and, most likely, fitness costs and their compensation. ICEs outnumber conjugative plasmids, suggesting an important role during bacterial evolution, yet they still have been largely overlooked as vectors of AR. Overall, ICE–bacterium coevolution appears to vary from plasmid–bacterium coevolution. ICE–bacterium dynamics thus represents a promising focus for future research on bacterial evolution and AR spread. Mobile genetic elements (MGEs), such as plasmids and integrative and conjugative elements (ICEs), are main drivers for the spread of antibiotic resistance (AR). Coevolution between bacteria and plasmids shapes the transfer and stability of plasmids across bacteria. Although ICEs outnumber conjugative plasmids, the dynamics of ICE–bacterium coevolution, ICE transfer rates, and fitness costs are as yet largely unexplored. Conjugative plasmids and ICEs are both transferred by type IV secretion systems, but ICEs are typically immune to segregational loss, suggesting that the evolution of ICE–bacterium associations varies from that of plasmid–bacterium associations. Considering the high abundance of ICEs among bacteria, ICE–bacterium dynamics represent a promising challenge for future research that will enhance our understanding of AR spread in human pathogens. Mobile genetic elements (MGEs), such as plasmids and integrative and conjugative elements (ICEs), are main drivers for the spread of antibiotic resistance (AR). Coevolution between bacteria and plasmids shapes the transfer and stability of plasmids across bacteria. Although ICEs outnumber conjugative plasmids, the dynamics of ICE–bacterium coevolution, ICE transfer rates, and fitness costs are as yet largely unexplored. Conjugative plasmids and ICEs are both transferred by type IV secretion systems, but ICEs are typically immune to segregational loss, suggesting that the evolution of ICE–bacterium associations varies from that of plasmid–bacterium associations. Considering the high abundance of ICEs among bacteria, ICE–bacterium dynamics represent a promising challenge for future research that will enhance our understanding of AR spread in human pathogens. a strategy for maximizing the geometric mean (and thus long-term) fitness across different environmental conditions at the cost of suboptimal fitness in individual environments. a process involving reciprocal adaptive changes between two or more genetic entities. secondary-site mutations that ameliorate the fitness cost of beneficial mutations, such as those encoding antibiotic resistance. contact-dependent transfer of genetic material between cells through a type IV secretion system. the trade-off observed when a mutation/gene leads to a selective advantage in one fitness-associated trait (e.g., antibiotic resistance) yet simultaneously a disadvantage in another fitness-associated trait (e.g., reduced growth rate). also called lateral gene transfer, HGT involves the movement of genetic material between genomes. previously known as conjugative transposons, ICEs are chromosomally integrated mobile elements that can be transferred horizontally between cells by conjugation. a genetic element that stockpiles and shuffles gene cassettes through site-specific recombination. an autonomous self-replicating extrachromosomal element that can be transferred horizontally between cells by conjugation. also called jumping genes, transposons are intracellular mobile elements that can 'jump' to different regions of the genome. when integrated in the host, this ICE exists as three separate chromosomal regions that recombine to form a single region before excision and conjugative transfer.