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Bacillus pumilus 15.1, a Strain Active against Ceratitis capitata, Contains a Novel Phage and a Phage-Related
Alberto Fernández-Fernández1, Antonio Osuna1, Susana Vilchez1,2
1Institute of Biotechnology, Faculty of Sciences, University of Granada, 18071 Granada, Spain.
Abstract:
A 98.1 Kb genomic region from B. pumilus 15.1, a strain isolated as an entomopathogen toward C. capitata, the Mediterranean fruit fly, has been characterised in search of potential virulence factors. The 98.1 Kb region shows a high number of phage-related protein-coding ORFs. Two regions with different phylogenetic origins, one with 28.7 Kb in size, highly conserved in Bacillus strains, and one with 60.2 Kb in size, scarcely found in Bacillus genomes are differentiated. The content of each region is thoroughly characterised using comparative studies. This study demonstrates that these two regions are responsible for the production, after mitomycin induction, of a phage-like particle that packages DNA from the host bacterium and a novel phage for B. pumilus, respectively. Both the phage-like particles and the novel phage are observed and characterised by TEM, and some of their structural proteins are identified by protein fingerprinting. In addition, it is found that the phage-like particle shows bacteriocin activity toward other B. pumilus strains. The effect of the phage-like particles and the phage in the toxicity of the strain toward C. capitata is also evaluated.
Insights
This study characterizes a genomic region in Bacillus pumilus, revealing phage-related elements. These elements produce novel phage particles with bacteriocin activity, potentially influencing entomopathogenicity.
Area of Science:
- Microbiology
- Genomics
- Virology
Background:
- Bacillus pumilus is an entomopathogen of the Mediterranean fruit fly, Ceratitis capitata.
- Genomic characterization of B. pumilus can identify virulence factors.
- Phage-related elements are often found in bacterial genomes and can influence host interactions.
Purpose of the Study:
- To characterize a 98.1 Kb genomic region of B. pumilus 15.1 for potential virulence factors.
- To investigate the function and origin of two distinct regions within the characterized genomic area.
- To determine the role of these regions in the production of phage-like particles and novel phages.
Main Methods:
- Comparative genomic analysis of B. pumilus 15.1.
- Mitomycin induction to stimulate phage production.
- Transmission Electron Microscopy (TEM) for phage visualization.
- Protein fingerprinting for structural protein identification.
Main Results:
- The 98.1 Kb region contains numerous phage-related open reading frames (ORFs).
- Two regions of different phylogenetic origins were identified: a conserved 28.7 Kb region and a rare 60.2 Kb region.
- These regions are responsible for producing a phage-like particle and a novel phage upon induction.
- The phage-like particle exhibits bacteriocin activity against other B. pumilus strains.
- TEM confirmed the presence and structure of the phage-like particles and the novel phage.
Conclusions:
- The characterized genomic regions in B. pumilus are crucial for producing novel phage particles.
- The phage-like particle possesses bacteriocin activity, suggesting a role in intraspecies competition.
- Further research is needed to fully elucidate the impact of these phages on the entomopathogenicity of B. pumilus.
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