Genome, biology and stability of the Thurquoise Phage - a new virus from the Bastillevirinae subfamily

Abstract

BackgroundBacteriophages from the Bastillevirinae subfamily have proven effective against bacteria from the Bacillus genus including organisms from B. cereus group which causes food poisoning and persistent contamination of industrial installations. However, successful application of these phages in biocontrol depends on understanding of their biology and stability in different environments.MethodsIn this study we isolated a novel virus from the garden soil in Wrocław (Poland) and named it Thurquoise. Genome of the phage was sequenced using Illumina technology and assembled as a single continuous contig that represents consensus result of different assembly algorithms. Its morphology was determined using Cryo-EM imaging while the dynamics of replication by turbidimetric lysis assay. We also determined phage host range in the efficiency of plating (EOP) assay. Finally, the stability of the Thurquoise was tested by long term incubation in buffers containing different ions (Mg2+, Ca2+, Mn2+, Zn2+, Cu2+, K+, Co2+, Fe3+, Cs+) and freezing with various cryoprotectants (glycerol, gelatin, saccharose, trehalose).ResultsWe present a complete, carefully annotated genome of the Thurquoise phage with 226 identified protein genes and 18 tRNAs. The complex virion structure of this phage is typical for the Bastillevirinae family. Confirmed hosts include selected bacteria from the Bacillus cereus group - specifically B. thuringiensis and B. mycoides. Latent and eclipse periods of Thurquoise in the isolation host last ~40 min and ~50 min respectively. The phage remains viable for more than 8 weeks in variants of SM buffer with magnesium, calcium, cesium, manganese or potassium and can withstand numerous freeze-thaw cycles if protected by the addition of 15% glycerol or, to a lesser extent, 2% gelatin.ConclusionThe Thurquoise phage is the exemplar of the new candidate species in Caruleovirus genus in the Bastillevirinae subfamily of the Herelleviridae family with genome, morphology and biology typical for these taxa.With proper buffer formulation, this virus (and likely related phages) can be safely stored in common freezers and refrigerators for a considerable time.