Characterization of Parageobacillus Bacteriophage vB_PtoS_NIIg3.2—A Representative of a New Genus within Thermophilic Siphoviruses

Abstract

A high temperature-adapted bacteriophage, vB_PtoS_NIIg3.2 (NIIg3.2), was isolated in Lithuania from compost heaps using Parageobacillus toebii strain NIIg-3 as a host for phage propagation. Furthermore, NIIg3.2 was active against four strains of Geobacillus thermodenitrificans, and it infected the host cells from 50 to 80 °C. Transmission electron microscopy analysis revealed siphovirus morphology characterized by an isometric head (~59 nm in diameter) and a noncontractile tail (~226 nm in length). The double-stranded DNA genome of NIIg3.2 (38,970 bp) contained 71 probable protein-encoding genes and no genes for tRNA. In total, 29 NIIg3.2 ORFs were given a putative functional annotation, including those coding for the proteins responsible for DNA packaging, virion structure/morphogenesis, phage–host interactions, lysis/lysogeny, replication/regulation, and nucleotide metabolism. Based on comparative phylogenetic and bioinformatic analysis, NIIg3.2 cannot be assigned to any genus currently recognized by ICTV and potentially represents a new one within siphoviruses. The results of this study not only extend our knowledge about poorly explored thermophilic bacteriophages but also provide new insights for further investigation and understanding the evolution of Bacilllus-group bacteria-infecting viruses.

Bacteriophages of Thermophilic ‘Bacillus Group’ Bacteria—A Systematic Review, 2023 Update

“…The increasing number of discoveries of thermophages, including those infecting thermophilic ‘ Bacillus group’ species, provides a more complete understanding of thermophiles’ biology, the mechanisms of biochemical adaptations needed for life in high temperatures, and the evolution of thermophilic host–bacteriophage relationships. Especially interesting is the recent characterization of numerous thermophages that were isolated from compost heaps using G. thermodenitrificans and Parageobacillus strains as hosts for bacteriophage propagation [ 42 , 43 ].…”

“…4.9. vB_PtoS_NIIg3.2 (Unclassified Caudoviricetes, Siphovirus morphotype, Host G. thermodenitrificans) Bacteriophage vB_PtoS_NIIg3.2 (referred to here by its shorter name, NIIg3.2) was isolated from the compost heaps using the enrichment of phages in the source material technique, with the local isolate Parageobacillus toebii strain NIIg-3 as a host [43]. In addition, four G. thermodenitrificans strains (PT-4, NIIg-2, PK-11, and PK-3) were sensitive to NIIg3.2 (out of 46 thermophilic Bacillus-group bacterial strains tested).…”