Transfer of CRISPR-like activity of MIMIVIRE into Bacteria

Abstract

MIMIVIRE is a defence system utilized by lineage A Mimiviruses against Zamilon virophages. It is composed of a helicase, a nuclease and a gene of unknown function here named trcg (for Target Repeat-Containing gene), which contains four 15-bp repeats identical to the Zamilon sequence. Their silencing restored susceptibility to Zamilon, and the CRISPR-Cas4-like activity of the nuclease was recently characterised. We expressed these 3 genes after transformation of a modified strain of Escherichia coli made resistant to ampicillin, chloramphenicol and tetracycline. The virophage repeats were replaced with four repeats of 15 nucleotides identical to a sequence in the tetracycline resistance gene. The induction of the MIMIVIRE genes restored E. coli sensitivity to tetracycline; the tetracycline operon and its supporting plasmid harbouring the chloramphenicol resistance gene vanished. We therefore efficiently transferred the defence system MIMIVIRE from giant Mimivirus against virophage to E. coli to clear it from a plasmid.