In Silico Prophage Analysis of Halobacterium salinarum ATCC 33170

The extremophile Halobacterium salinarum is an aerobic archaeon that has adapted to thrive in high-salt environments such as salted fish, hypersaline lakes, and salterns. Halophiles have garnered significant interest due to their unique interactions with bacteriophages known as haloarchaeophages. Studies have identified and characterized prophages in halophilic archaea, such as Haloferax volcanii, Haloquadratum walsbyi, and Haloarcula marismortui. Still, an investigation has yet to be conducted into the presence of prophage elements on Halobacterium salinarum ATCC 33170. This is of particular interest to us as we are using this strain as a source of archaeol, as one of the components of our sulfated lactosyl archaeol (SLA) archaeosome adjuvant. Genomic contigs of strain 33170 were bioinformatically assessed for prophage-like features using BLAST, PHASTER, InterProScan, and PHYRE2. A 7 kb region encoding six genes was identified as an incomplete prophage, and the proteins were further analyzed, revealing high homology to proteins encoded by bacteria, archaea, and an IS200 transposon. Restricting the BLASTp database to viruses resulted in hits to both myo- and siphoviral proteins, which would be unusual for an intact prophage. Additionally, no known phage structural proteins were identified in the search, suggesting a low chance that H. salinarum ATCC 33170 harbors a latent prophage.