Pathogenic Vibrio Species Are Associated with Distinct Environmental Niches and Planktonic Taxa in Southern California (USA) Aquatic Microbiomes

Interactions between vibrio bacteria and the planktonic community impact marine ecology and human health. Many coastal Vibrio spp. can infect humans, representing a growing threat linked to increasing seawater temperatures. Interactions with eukaryotic organisms may provide attachment substrate and critical nutrients that facilitate the persistence, diversification, and spread of pathogenic Vibrio spp. However, vibrio interactions with planktonic organisms in an environmental context are poorly understood. We quantified the pathogenic Vibrio species V. cholerae, V. parahaemolyticus, and V. vulnificus monthly for 1 year at five sites and observed high abundances, particularly during summer months, with species-specific temperature and salinity distributions. Using metabarcoding, we established a detailed profile of both prokaryotic and eukaryotic coastal microbial communities. We found that pathogenic Vibrio species were frequently associated with distinct eukaryotic amplicon sequence variants (ASVs), including diatoms and copepods. Shared environmental conditions, such as high temperatures and low salinities, were associated with both high concentrations of pathogenic vibrios and potential environmental reservoirs, which may influence vibrio infection risks linked to climate change and should be incorporated into predictive ecological models and experimental laboratory systems. IMPORTANCE Many species of coastal vibrio bacteria can infect humans, representing a growing health threat linked to increasing seawater temperatures. However, their interactions with surrounding microbes in the environment, especially eukaryotic organisms that may provide nutrients and attachment substrate, are poorly understood. We quantified three pathogenic Vibrio species monthly for a duration of 1 year, finding that all three species were abundant and exhibited species-specific temperature and salinity distributions. Using metabarcoding, we investigated associations between these pathogenic species and prokaryotic and eukaryotic microbes, revealing genus and amplicon sequence variant (ASV)-specific relationships with potential functional implications. For example, pathogenic species were frequently associated with chitin-producing eukaryotes, such as diatoms in the genus Thalassiosira and copepods. These associations between high concentrations of pathogenic vibrios and potential environmental reservoirs should be considered when predicting infection risk and developing ecologically relevant model systems.