Accelerating Genome Evolution: New System Mimics Decades of Change in Weeks

A team at the University of Tokyo has developed a system to control and accelerate the evolution of changes in bacterial genome structure. This system targets small "jumping genes," or DNA sequences known as insertion sequences (ISs). The research bridges the gap between studying past evolution and observing real-time genetic changes in the lab. Researchers often study bacterial genomes due to their manageable size and consistency. Insertion sequences (ISs) are known to "jump" or change position within a genome, driving evolutionary change. These changes can result in mutations, reversals, or alterations in genome size and identity. To accelerate these changes, the team introduced multiple copies of high-activity ISs in Escherichia coli (E. coli). Within just 10 weeks, the test organisms accumulated changes similar to what occurs over decades in nature. This included about 25 new insertions of mobile genetic elements and a 5% change in genome size. The high IS activity resulted in structural variants and the emergence of composite transposons. This illuminates potential evolutionary pathways for ISs and composite transposons. The results provide a valuable reference for studying the effects of IS insertions and genome size changes. "Unexpectedly," said Yuki Kanai, the study also shed light on the evolution of transposons themselves. Kanai hopes to apply this system to broader questions, such as understanding the conditions under which cooperation evolves between bacteria or between bacteria and their hosts.