pGIL01, a linear tectiviral plasmid prophage from Bacillus thuringiensis serovar israelensis
(2004)
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- Authors
- Supervisors
- Mahillon, Jacques
- Abstract
- The Bacillus cereus sensu lato group includes six closely related bacteria, namely B. cereus sensu stricto, B. thuringiensis, B. anthracis, B. weihenstephanensis, B. mycoides and B. pseudomycoides. B. thuringiensis is an entomopathogenic strain used worldwide as bio-insecticide to control insect pests. More specifically, B. thuringiensis serovar israelensis is active against lepidopteran larvae, such as black flies and mosquitoes, two important vectors of human and animal diseases. The plasmid pattern analysis of B. thuringiensis serovar israelensis strain 4Q2-72 revealed the presence of at least eight plasmids, including four large and three small circular plasmids, as well as one unconventional linear element of 15kb. This linear molecule was reported for the first time in 1984 by Gonzàlez and Carlton but so far, no characterization of this small linear plasmid has been undertaken. The primary objective of the present work was therefore to establish a first description of this linear element, designated pGIL01, in order to get more insights concerning its contribution into the plasmid biology of B. thuringiensis. The first part of this thesis consisted in the genetic description of this linear molecule pGIL01. Its sequence analysis, as well as experimental evidences, revealed that pGIL01 is the prophage form of a temperate phage, named GIL01, that belonged to the Tectiviridae family. Members of this group are characterized by the presence of lipid components in their capsids. Both the plasmid prophage and the viral genomes possess the same linear ds DNA molecule of 14,931 bp protected by proteins at their 5'extremities and with imperfect terminal inverted repeats of 73 bp at both ends. These data establish, for the first time, the existence of a prophage existing as a linear element harbouring terminal proteins. The activity of two putative peptidoglycan hydrolases identified on (p)GIL01 have been experimentally confirmed. While both lytic enzymes are able to cleave Gram-positive peptidoglycan preparations, only one is active against Gram-negative bacteria. The second part of this study focused on the occurrence of (p)GIL01-related linear elements among the B. cereus sensu lato group. The genetic comparison of (p)GIL01 with three other (putative) Gram-positive tectiviruses (Bam35, GIL01 and pBClin15) and with the Gram-negative tectivirus PRD1 revealed that the Tectiviridae family is prone to extensive genetic flexibility.
- Affiliations
Citations
Verheust, C. (2004). pGIL01, a linear tectiviral plasmid prophage from Bacillus thuringiensis serovar israelensis. https://hdl.handle.net/2078.5/97512