Maurin, A. | bioRxiv Science

bioRxiv2025

The complete genome and comparative analysis of a new Tequintavirus: Salmonella phage Tennessee Salten

The rise in multidrug-resistant pathogenic bacteria presents a major current challenge, highlighting the urgent need for alternatives and sustainable biocontrol strategies. Here, we report the genome analysis of a bacteriophage called Salmonella phage Tennessee Salten and attributed to a new Tequintavirus species. Salten was isolated following infection of Salmonella enterica subsp. enterica serotype Tennessee (sequence type ST5018). Its genome is 109,999 bp in length and contains 220 predicted proteins on which 197 are CDS and 23 tRNAs. Compared to its closest known relative phage Escherichia phage HildyBeyeler - sharing 84.6% identity - Salten harbours 16 unique or highly divergent genes. Of these, 13 encode proteins with unknown function, one encodes for a putative adenine methyltransferase and two encode HNH homing endonucleases. Moreover, the Long Tail Fibre protein, whose structure was predicted based on that of phage T5, was highly divergent among the Tequintavirus genus.

microbiology↗

bioRxiv2024

"This training is bound for glory": selection by experimental evolution of a bacteriophage with expanded host-range and increased virulence

Viral host range expansion is predicted to evolve at the cost of reduced mean fitness. We investigated the adaptive walks of a virulent phage (Tequintavirus) in a spatially variable environment composed of four susceptible bacterial isolates and four resistant ones (Salmonella enterica serotype Tennessee, sequence types ST5018 and ST319 respectively). Starting from a single ancestral phage, we evolved multiple independent populations through serial passages on non-coevolving bacteria, following the Appelmans protocol. The phage populations evolved an expanded host range and increased virulence. Whole-genome sequencing revealed recurrent parallel mutations across populations (i.e. convergent evolution), particularly in genes encoding exo- and endo-nucleases, dUTPase, and caudal proteins. Notably, two parallel mutations in the gene coding for the Long Tail Fibre became fixed early in the evolutionary trajectories. Reverse-genetics experiments introducing these mutations into the ancestral genome expanded the host range but yielded only marginal increases in virulence, highlighting the effect of compensatory mutations. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=115 SRC="FIGDIR/small/584857v3_ufig1.gif" ALT="Figure 1"> View larger version (24K): org.highwire.dtl.DTLVardef@cec6b5org.highwire.dtl.DTLVardef@1579ba4org.highwire.dtl.DTLVardef@ab5ad5org.highwire.dtl.DTLVardef@1d88160_HPS_FORMAT_FIGEXP M_FIG C_FIG Highlights* A phage (Tequintavirus) was evolved on susceptible and resistant Salmonella enterica strains * Experimentally evolved phage populations displayed expanded host range and increased virulence * Convergent evolution revealed adaptive mutations modifying receptor recognition in caudal proteins * Reverse-genetic showed implication of two Long Tail Fibre mutations in host range expansion In BriefGeneralism is traditionally predicted to evolve at the cost of lower mean fitness. Contrary to this textbook view, we demonstrate that generalist phages with expanded host range and increased virulence can readily evolve in vitro and be purposely optimized for phage therapy applications.

evolutionary biology↗