Plasmidial tectiviruses infecting the Bacillus cereus group: friends or foes ?
(2016) International Society for Plasmid Biology Scientific Meeting 2016 — Location: Cambridge, United Kingdom (18.September.2016)
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- Abstract
- Tectiviridae is a rare phage family comprising non-enveloped tail-less phages, with a double-layer capsid where the ~15 kb linear dsDNA is located within a lipid-containing membrane covered by a rigid icosahedral protein capsid. Since tectiviruses are, so far, the only phages infecting the Bacillus cereus group able to behave as linear plasmids during their lysogenic cycle1, it is important to assess the potential contribution of this type of elements to the genetic diversity of their hosts and to understand the selective pressures experienced by the bacteria when facing these phages. This work focuses on characterizing the interactions between tectiviruses and the B. cereus group, mainly by assessing their occurrence, genetic diversity and addressing the question of whether or not temperate tectiviruses influence their hosts’ life traits. Screening of a worldwide collection of B. cereus s.l. strains and propagation tests indicated that tectiviruses occurred in less than 3% of the bacterial isolates. Notwithstanding this limited distribution, partial DNA sequencing uncovered novel tectiviruses2, some of them with ORFans in regulatory regions involved in lysogeny maintenance3. Analysis of the tectiviruses host range showed that no simple relationship could be established between the infection patterns of these phages and their diversity. However, the data revealed that tectiviruses in the B. cereus group clustered into two major groups: the ones infecting Bacillus anthracis and those isolated from other B. cereus group members2. Interesting tectiviral plasmid-related molecules with recombinant characteristics were also discovered by analyses of whole genome sequences. Additionally, it was found that tectiviral lysogeny had a significant influence on the bacterial growth, sporulation rate, biofilm formation, and swarming motility of their Bacillus thuringiensis host4, all of which are traits involved in the survival and colonization of this bacterium in different environmental habitats. Overall, these findings provide evidence that not only tectiviruses are more diverse than previously thought, but they also have ecological roles in the already complex life cycle of B. thuringiensis and kin.
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Gillis, A., & Mahillon, J. (2016). Plasmidial tectiviruses infecting the Bacillus cereus group: friends or foes ? International Society for Plasmid Biology Scientific Meeting 2016, Cambridge, United Kingdom. https://hdl.handle.net/2078.5/221019