Is the diatom Chaetoceros muelleri a vector for the enteric pathogen Vibrio cholerae?

Abstract

Cholera has been around for centuries, with the seventh pandemic ongoing since 1961. Unfortunately, global warming and climate change will likely promote its persistence through multifaceted effects. Chitin-containing vectors, primarily zooplanktons, help facilitate the spread of Vibrio cholerae, the causative agent of cholera. However, climate-associated algal blooms are hypothesised to play a role, as many phytoplanktons also contain chitin. In Singapore, Chaetoceros muelleri is one of the dominant phytoplankton species. In this study, the potential role of C. muelleri as a vector for V. cholerae was explored through co-culture assays, chemotaxis assays and attachment assays. A pandemic-generating strain, EDC721, and a non-pandemic strain from the same environment, EDC688, were tested, along with a genetically traceable pandemic-generating strain, C6706. It was found that co-culturing V. cholerae with C. muelleri greatly benefitted the former, with some mutualistic effect on the latter. This supported C. muelleri as an effective vector. However, C. muelleri did not secrete a detectable level of chemoattractant in the chemotaxis assays. Fluorescence microscopy in short-duration attachment assays revealed largely sporadic interactions between both species. Overall, these findings provided a roadmap for more comprehensive characterisations of the interactions between V. cholerae and C. muelleri.