Abstract EANA2025-73

The study of halophiles is crucial for understanding the boundaries of life, and expanding our toolkit of model halophiles with new, tractable isolates is essential for exploring the full diversity of microbial adaptation to high-salinity environments. Droitwich Spa, a stable, historic hypersaline brine in the UK, presents an ideal source for such novel candidates. We have isolated and characterised a unique strain, Vreelandella sp. D1, from this environment and propose it here as a new model system for halophile research.

Vreelandella sp. D1 was isolated on halophilic media, and its genome was sequenced using both Illumina and Nanopore platforms to generate a higher coverage genome that was assembled with hybridSpades. Comprehensive bioinformatic analyses were performed to define its taxonomy, metabolic potential, biosynthetic gene clusters (BGCs), and mobile genetic elements. Further pangenomic analysis enabled identification of genes unique to these Droitwich isolates. The metabolic potential of D1 was functionally verified via a combination of Biolog plates and screening against ESKAPE pathogens. The presence of lysogenic bacteriophage tested via induction assays.

Vreelandella sp. D1 was readily culturable from the hypersaline brine and grows rapidly, reaching maximum optical density in two days. The annotated genome provides a stable platform for genetic studies and was tractable with a crispr technique. Genomic analysis identified genes encoding the complete denitrification pathway and extensive carbon utilisation pathways, with functionality confirmed via testing of cultures with biology plates. Pangenomic analysis identified numerous additional adaptations to hypersalinity in Vreelandella sp. D1 that were absent within the genus. The function of BGCs was confirmed by the strain's antimicrobial activity against several ESKAPE pathogens, making it a suitable model for metabolite production under salt stress. Furthermore, the genome contains a complete, inducible prophage, offering a tractable system for investigating virus-host dynamics in hypersaline conditions.

Vreelandella sp. D1 possesses a combination of features that make it an ideal model organism: it is easily cultivated, genetically tractable, a facultative anaerobe, produces bioactive compounds, and hosts an inducible phage. This isolate represents a possible tool for deeper investigation into the molecular mechanisms of halophilic adaptation, the discovery of novel bioactive molecules, and the ecological role of bacteriophages in extreme environments.