Bacteriophages are the most abundant biological entities in the oceans and play key roles in bacterial activity, diversity and evolution. While extensive research has been conducted on the role of tailed viruses (Class: Caudoviricetes), very little is known about the distribution and functions of the non-tailed viruses (Class: Tectiliviricetes). The recent discovery of the lytic Autolykiviridae family demonstrated the potential importance of this structural lineage, emphasizing the need for further exploration of the role of this group of marine viruses. Here we report the novel family of temperate phages under the class of Tectiliviricetes, which we propose to name “Asemoviridae” with phage NO16 as a main representative. These phages are widely distributed across geographical regions and isolation sources and found inside the genomes of at least 30 species of Vibrio in addition to the original V. anguillarum isolation host. The interactions between the NO16 phage and its V. anguillarum host were linked to cell density and phage-host ratio. High cell density and low phage predation levels were shown to favour the temperate over the lytic lifestyle for NO16 viruses, and their spontaneous induction rate was highly variable between different V. anguillarum lysogenic strains. NO16 prophages coexist with the V. anguillarum host in a mutualistic interaction by rendering fitness properties to the host, such as increased virulence and biofilm formation through lysogenic conversion, likely contributing to their global distribution.

Primary Presenter: Mathias Middelboe, Københavns Universitet, Biologisk Institut (mmiddelboe@bio.ku.dk)

Authors:

Panos Kalatzis, University of Copenhagen  (panos.kalatzis@adisseo.com)

Jesper Mauritzen, University of Copenhagen  ()

Caroline Winther-Have, University of Copenhagen  ()

Slawomir Michniewski, University of Warwick  ()

Andrew Millard, University of Leicester  ()

Maria Tsertou, Hellenic Center for Marine Research  ()

Pantelis Katharios, Hellenic Center for Marine Research  ()