Characterization of Nhi, a novel anti-bacteriophage defense system

Van Brussel, Gaƫtan
(2026)

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VanBrussel_59631900_2026_Annexe.pdf
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Details

Supervisors
Gillis, Annika
Faculty
FacultƩ des bioingƩnieurs
Degree label
Master [120] : bioingƩnieur en sciences agronomiques, Ơ finalitƩ spƩcialisƩe
Abstract
The arms race between bacteria and (bacterio)phages is a long-lasting fight to have the upper hand against each other. Bacteria developed anti-phage defense systems to keep their integrity. The nuclease-helicase immunity (Nhi) system is a novel anti-phage defense system discovered in 2022 and proved to protect Staphylococcus aureus against bacteriophages. In this study, Nhi activity was investigated in Escherichia coli, Bacillus thuringiensis, and Staphylococcus aureus through bacteria-phage confrontations and plasmid transfer assays. The pMAD and pLI50 plasmids are used as vectors to study the Nhi defense system in the different bacterial strains. No significant antiviral activity was detected against the tested phages in the different bacterial strains. However, Nhi expression appeared to reduce the plasmid transfer of the pXO16 plasmid in B. thuringiensis. These results suggest that Nhi may play a role in limiting horizontal gene transfer between Bacillus cereus group bacteria. This work also provides novel insight on the Nhi defense system activity.