Viral isolation reveals novel and diverse phages infecting natural stream biofilms

Bacteriophages of environmental bacteria remain underrepresented, lending paucity to phage-biofilm research beyond clinical and model species domains. Here, we present the Alpine Lotic Phage (ALP) collection, curated through an isolation campaign from biofilm-forming bacteria of alpine streams. We obtained 57 phage isolates, which were dereplicated to 28 unique genomes following sequencing. The collection consists of tailed phages infecting 14 bacterial host species with genomes spanning 37 to 363 kb while exhibiting diverse plaque morphologies, depolymerase activity, and distinct impacts on host biofilm architecture. Comparative analyses against public viral genomes and a curated planetary-scale contig database revealed limited sequence similarity, underscoring the novelty of ALP phages. Functional annotation resolved 9 - 54% of predicted genes which encoded viral structural components, nucleotide metabolism functions, anti-defence mechanisms, and auxiliary genes that facilitate viral infection and replication. Together, the ALP collection represents a foundational resource for investigating phage evolution and ecology in natural bacterial communities.