Ganz et al. - 2014 - Novel giant siphovirus from Bacillus anthracis features unusual genome characteristics

Abstract

  • Introduction of novel temperate phage vB_BanS-Tsamsa isolated from Bacillus anthracis.

  • Phage Tsamsa is categorized as a giant siphovirus (order Caudovirales):

    • Long, flexible tail (440 nm) and isometric head (82 nm).

  • Genome size: 168,876 bp, 272 ORFs.

  • Exhibits an integrase/recombinase enzyme indicative of a temperate lifestyle.

  • Specific to certain Bacillus cereus sensu lato group members (B. anthracis, B. cereus, B. thuringiensis).

  • Lysed 7 out of 25 tested B. cereus strains, 2 out of 5 B. thuringiensis, and 6 out of 7 B. anthracis strains.

  • Shows promise for use in Bacillus biocontrol due to broader lytic spectrum of endolysin.

Introduction

  • Investigation of Bacillus anthracis, causing anthrax in wildlife, livestock, and humans.

  • Bacillus cereus sensu lato group includes species with pathogenic traits:

    • B. cereus: food poisoning, opportunistic infections.

    • B. thuringiensis: insect pathogen used in agriculture.

  • Lysogeny is a common phenomenon in B. anthracis which may be crucial for its life cycle.

    • B. anthracis from soil often exhibit phage-derived plaques.

  • Temperate phages can impact sporulation and biofilm formation in B. anthracis.

Materials and Methods

  • Phage isolation from carcass and soil samples in Etosha National Park, Namibia.

  • Diagnostic testing confirmed the presence of anthrax in carcasses (genotypes 6 and 4).

  • Phages isolated by bacterium culturing and prophage induction with mitomycin C.

  • Two methods for phage culturing:

    1. Swab isolate: overnight culture in BHI medium followed by mitomycin C induction.

    2. Soil sample: assisted by nutrient broth to extract phages from soil.

Phage Host Range

  • Tested 55 bacterial strains for susceptibility to Tsamsa phage; results show selective infection characteristics.

  • Unable to infect several strains, indicating a narrow host range with moderate specificity for B. anthracis.

Phage Morphology

  • Tsamsa phage morphology characterized by:

    • Length: 440 nm (tail), Diameter: 82 nm (head).

    • Identifiable features through electron microscopy.

Genome Sequencing and Characteristics

  • Genome comprises 168,876 bp with 272 ORFs and 17 tRNA genes.

  • GC content is 34%, similar to B. anthracis genomes.

  • Genome exhibits complex structure with potential gene product functions indicated.

Endolysin Production

  • Tsamsa phage endolysin produced recombinantly, exhibiting broad lytic activity against various Bacillus strains.

  • Assessed through turbidity reduction and plate lysis assays.

Discussion

  • Tsamsa phage uniquely identified as one of the largest isolated siphoviruses, surpassing 9 of 539 previously sequenced genomes.

  • Presence of three tyrosine integrases highlights the temperate nature of the phage and its potential to integrate into host genomes.

  • Features of structural proteins indicate potential amplification of host range.

  • Suggested usefulness in antimicrobial applications targeting Bacillus infections through the endolysin.

Acknowledgments

  • Thanks given to contributors and support staff for logistical and analytical help during the research process.

References

  • Cited various peer-reviewed studies and references to substantiate claims and findings.