Wildfire ashes from the Wildland Urban Interface alter Vibrio vulnificus growth and gene expression

Climate change-induced stressors are contributing to the emergence of infectious diseases, including those caused by marine bacterial pathogens such as Vibrio spp. These stressors alter Vibrio temporal and geographical distribution, resulting in increased spread, exposure, and infection rates, thus facilitating greater Vibrio-human interactions. Concurrently, wildfires are increasing in size, severity, frequency, and spread in the built environment due to climate change, resulting in the emission of contaminants of emerging concern. This study aimed to understand the potential effects of urban-interface wildfire ashes on V. vulnificus growth and gene expression using transcriptomic approaches. V. vulnificus was exposed to structural and vegetative ashes and analyzed to identify differentially expressed genes using the HTSeq-DESeq2 strategy from the Bacterial and Viral Bioinformatics Resource Center. Exposure to wildfire ash altered V. vulnificus growth and gene expression depending on the trace metal composition of the ash. The high Fe content of the vegetation ash enhanced bacterial growth while the high Cu, As, and Cr content of the structural ash suppressed growth. Additionally, the overall pattern of upregulated genes and pathways suggests increased virulence potential due to the co-selection of metal and antibiotic resistance. Therefore, mixed fire ashes transported and deposited into coastal zones may lead to the selection of environmental reservoirs of Vibrio strains with enhanced virulence profiles, increasing public health risk.