Flow cytometry-based biomarker assay for in vitro identification of microalgal symbionts conferring heat tolerance on corals

Abstract

Corals’ tolerance to high temperature stress largely depends on their symbiotic microalgae (Symbiodiniaceae). However, the contributing microalgal traits and their relationships to one another are largely unclear. Here we compare the in vitro cellular profiles of seven Cladocopium C1acro microalgal strains (derived from the same ancestral strain) during a four-week exposure to 27°C or 31°C. One was an unselected wild-type strain (WT), three were selected at 31°C for nine years and shown to confer thermal tolerance on the coral host (SS+) and three others were similarly selected but did not confer tolerance (SS-). Flow cytometry was used to measure the staining intensities of cells treated wi..