Tectiviruses preying on the Bacillus cereus group: prevalence, phage-host interactions and host life-traits changes
(2012) The 14th International Symposium on Microbial Ecology - ISME14 — Location: Copenhagen, Denmark (19.August.2012)
Files
ISME14_2012_Copenhagen_Tectivirus.pdf
Restricted Access - Adobe PDF
- 2.39 MB
Details
- Authors
- Abstract
- The Bacillus cereus group includes several species displaying distinct virulence spectra as diverse as mammal anthrax caused by Bacillus anthracis, food toxi-infection due to B. cereus or the entomopathogenic activity of Bacillus thuringiensis. Many of these differences are associated with Mobile Genetic Elements (MGE), including plasmids, insertion sequences or transposons and phages. Nevertheless, little is known about the potential contribution of MGE, and particularly phages, to the adaptation of the B. cereus group members to diverse ecological niches. One interesting phage family infecting the B. cereus group is Tectiviridae comprising non-enveloped tail-less phages with a double-layer capsid where the ~15kb linear dsDNA is located within a lipid-containing membrane covered by a rigid icosahedral protein capsid. This family contains two groups of phages: the lytic PRD1 infecting Gram-negative bacteria such as Escherichia coli and Salmonella enterica, and the temperate ones preying on Gram-positive bacteria belonging to the Bacillus cereus sensu lato (s.l.) group. Phages Bam35 (or GIL01), GIL16 and AP50 are representatives of the latter tectivirus group. Additionally, these phages exhibit a strong similarity to the B. cereus linear plasmid pBClin15. Although the biology of PRD1 is well studied, little is known about the interactions taking place between tectiviruses and their respective Gram-positive hosts. Therefore, this work aimed at characterizing the interactions between tectiviruses and their B. cereus s.l. host cells. Due to the fact that temperate tectiviruses are able to reside as linear plasmid, the occurrence of tectiviral elements was addressed among nearly 2,000 B. cereus s.l. strains and very closely related bacteria isolated worldwide. PCR and propagation tests revealed that tectiviral elements occurred in less than 5% of the examined strains. Despite this limited distribution, some novel tectivirus were found, and DNA sequencing of variable regions indicated that a greater diversity exist within the Tectiviridae. In an effort to assess the host range of GIL01, GIL16 and their new cousins, 100 strains of B. cereus s.l. devoid of tectiviral-like elements were tested. The results showed that ca. 30% of the bacteria were sensitive to the tectiviruses tested. Interestingly, some strains were susceptible to both GIL01 and GIL16, whereas others could be infected only by one representative. These results strongly suggest that more than one molecule can act as tectivirus receptor on the bacterial surface. For studying adsorption properties and identification of tectivirus receptors, spontaneous as well as transposon-induced bacterial mutant libraries were obtained and mutants displaying either complete or specific phage resistances were obtained. Bacterial mutants displaying complete resistance to tectivirus exhibited various colony morphotypes and showed distinct adaptation features, as illustrated by their biofilm formation and exopolysaccharide production, changes in conjugation frequency of some B. thuringiensis plasmids, sporulation rate and long-term survival capacity. These observations indicate that tectiviruses may drive life-trait changes and ecological adaptations in the B. cereus group members. These results will shed new light on bacteriophages receptor(s) and on the bacterial adaptation strategies to phage life-styles.
- Affiliations
Citations
Gillis, A., & Mahillon, J. (2012). Tectiviruses preying on the Bacillus cereus group: prevalence, phage-host interactions and host life-traits changes. The 14th International Symposium on Microbial Ecology - ISME14, Copenhagen, Denmark. https://hdl.handle.net/2078.5/194972