Differentially Expressed Virulence Genes in Shewanella algae from a Deceased Northern Bottlenose Whale

Diseases are an important but poorly understood influence on marine ecosystems. However, many pathogens of wild marine organisms remain poorly characterised, limiting our understanding of their ecology and potential impacts. This study investigates the virulence mechanisms of a pathogenic Shewanella algae strain isolated from the brain tissue of a deceased northern bottlenose whale (Hyperoodon ampullatus). Using high-resolution Oxford Nanopore RNA Sequencing, differential gene expression (DGE) analysis was conducted comparing growth in standard media, Tryptic Soy Broth (TSB) and TSB supplemented with 5% brain homogenate (BH) to stimulate expression of virulence-associated genes. Twenty-three significantly differentially expressed genes (DEGs) were identified out of 7,213 actively expressed genes, highlighting processes linked to bacterial virulence, such as protein translocation (e.g., sSRP RNA), flagellar motility, chemotaxis, and iron uptake. Functional analysis indicated an increased expression of pathways related to amino acid metabolism and motility, whereas carbohydrate and inorganic ion transport were downregulated. These results suggest that environmental cues, potentially included factors related to iron metabolism, may influence bacterial virulence, and demonstrate the effectiveness of Oxford Nanopore RNA sequence for pathogen transcriptomics.