The Tn4371 ICE family of bacterial mobile genetic elements

The Tn4371 ICE (Integrative Conjugative Element) family refers to a group of mobile genetic elements with four modules containing genes involved in integration (via a tyrosine‑based site‑specific recombinase), maintenance/stability, accessory genes conferring a special phenotype to the host bacteria and genes involved in conjugational transfer. The latter display similarity with conjugative genes of Ti plasmids and IncP broad host range plasmids. Currently this ICETn4371 family harbours around 40 elements with sizes ranging from 38 to 101 kb. Elements carrying accessory genes, which are mostly flanked by the conjugative genes rlxS (virD2) and traR, reside in Beta‑ and Gammaproteobacteria, while elements in Alphaproteobacteria apparently lack accessory genes and display a more divergent pattern. Accessory genes have very diverse functions including catabolism of xenobiotic compounds, resistance to heavy metals, to antibiotics, chemolithotrophic metabolism, but also some unknown functions. Strains from man‑made environments (sewages, industrial wastes and clinical settings) are predominant among the bearers of Tn4371 ICEs next to plant pathogens, which are also well represented. Insights into ~30 characteristic genes (such as those encoding site‑specific recombinases and excisionases) as well as their distribution in the described elements and their relationship with other mobile genetic elements is provided.