Integrative Biology

Biography

Biography: Rinat Arbel-Goren

Abstract

During horizontal gene transfer processes, imported exogenous DNA sequences integrate at unique sites in the host bacterial genome, driving genetic diversity. One example is viral infection, which is known to allow the acquisition of pathogenic traits.After entering an Escherichia coli cell, the ∼5x10⁴-long bacteriophage λ DNA must locate a unique site among ∼5x10⁶ possible sites on the bacterial genome, with high efficiency and within physiological times, to integrate and establish lysogeny. What are the mechanisms that allow it to do it?We followed the targeting process in individual live E. coli cells in real-time, by marking fluorescently both the phage DNA after entry into the host, and a chromosomal sequence near the integration site. Surprisingly, we found that λ DNA does not carry out an active search. Instead, it remains confined near its entry point into the cell following infection, preferentially at the poles, where it undergoes limited diffusion. The encounter between the 15 bp-long target sequence on the chromosome and the recombination site on the viral genome is facilitated by thedirected motion of bacterial DNA generated during chromosome replication and segregation.A different mechanism of target location is observed during conjugation betweenB. subtilis cells:  integrating conjugating elements imported from donor cells carry out anomalous diffusion within host cellsin their search for their target insertion sites, which move concomitantly, driven by replication of the host genome. These finding demonstrate that there are different solutions to the target location problemduring horizontal gene transfer processes.