Many species of coastal Vibrio spp. bacteria can infect humans, representing an emerging health threat linked to increasing seawater temperatures. Vibrio interactions with the planktonic community impact coastal ecology and human infection potential. In particular, interactions with eukaryotic and photosynthetic organism may provide attachment substrate and critical nutrients (e.g. chitin, phytoplankton exudates) that facilitate the persistence, diversification, and spread of pathogenic Vibrio spp.. Vibrio interactions with these organisms in an environmental context are, however, poorly understood.
After quantifying pathogenic Vibrio species, including V. cholerae , V. parahaemolyticus , and V. vulnificus, over one year at 5 sites, we found that all three species reached high abundances, particularly during Summer months, and exhibited species-specific temperature and salinity distributions. Using metabarcoding we established a detailed profile of the both prokaryotic and eukaryotic coastal microbial communities, finding that pathogenic species were frequently associated with specific ASVs of chitin-producing eukaryotes such as diatoms and copepods. Furthermore, environmental variables had a significant effect not only on pathogenic Vibrio species but entire microbial communities, suggesting in some cases shared environmental preferences. Several significant ASV-level associations were revealed, indicating that commonly used broad taxonomic classifications (e.g. based on microbial class or Vibrio as a genus) likely mask ecologically important interactions. Shotgun metagenomic analyses revealed diverse vibrio communities that harbored additional potential vibrio pathogens, antibiotic resistance genes, and genes associated with virulence.
Taken together, this data shows that abundant pathogenic Vibrio species likely containing both antibiotic resistance and virulence-associated genes are associated with chitin producing organisms which could act as an attachment substrate, facilitating environmental persistence and horizontal gene transfer. Shared environmental conditions such as high temperatures were associated with both high levels of pathogenic vibrios and potential environmental reservoirs, which should be taken into consideration when modelling vibrio infection risk in the face of climate change and identifying biomarkers of pathogen species. Furthermore, ASV-level associations may be critical to understanding vibrio microbial ecology and should be taken into consideration while developing environmentally relevant laboratory model systems.