Coral symbiotic algae calcify ex hospite in partnership with bacteria

Abstract

Dinoflagellates of the genus Symbiodinium are commonly recognized as invertebrate endosymbionts that are of central importance for the functioning of coral reef ecosystems. However, the endosymbiotic phase within Symbiodinium life history is inherently tied to a more cryptic free-living (ex hospite) phase that remains largely unexplored. Here we show that free-living Symbiodinium spp. in culture commonly form calcifying bacterial-algal communities that produce aragonitic spherulites and encase the dinoflagellates as endolithic cells. This process is driven by Symbiodinium photosynthesis but occurs only in partnership with bacteria. Our findings not only place dinoflagellates on the map of microbial-algal organomineralization processes but also point toward an endolithic phase in the Symbiodinium life history, a phenomenon that may provide new perspectives on the biology and ecology of Symbiodinium spp. and the evolutionary history of the coraldinoflagellate symbiosis.Symbiodinium | coral symbiont | microbial-algal calcification | endolithic algae | life history

Cell Cycle Dynamics of Cultured Coral Endosymbiotic Microalgae (Symbiodinium) Across Different Types (Species) Under Alternate Light and Temperature Conditions

“…; Frommlet et al. ; Suggett et al. ), few studies have yet examined the Symbiodinium cell cycle to resolve premitotic control of Symbiodinium cell densities by their hosts (Dimond et al.…”

“…Despite the ever-intensifying interest in resolving Symbiodinium biology (e.g. Davy et al 2012;Frommlet et al 2015;Suggett et al 2017), few studies have yet examined the Symbiodinium cell cycle to resolve premitotic control of Symbiodinium cell densities by their hosts (Dimond et al 2013;Smith and Muscatine 1999). Growth status of Symbiodinium is important for maintaining a stable symbiosis with the host (e.g.…”

The short-term combined effects of temperature and organic matter enrichment on permeable coral reef carbonate sediment metabolism and dissolution

“…The sediments were net calcifying during the day under all treatment conditions, which was likely due to a combination of light-stimulated biogenic calcification by infaunal organisms (e.g. symbiont-bearing foraminifera: Yamano et al, 2000; or dinoflagellates: Frommlet et al, 2015) and by a photosynthetically mediated increase in porewater aragonite saturation state to a value that would allow for abiotic precipitation ( > 8; Cohen and Holcomb, 2009). However, the exact organisms and geochemical conditions responsible for the measured net diurnal calcification signal was beyond the scope of this study and should be examined in future work.…”

Revealing changes in the microbiome of Symbiodiniaceae under thermal stress

“…Bacteria can play critical roles in regulating the metabolic functioning and growth of their phytoplankton associates (e.g. Seymour et al ., ), and Symbiodiniaceae associated bacteria are no exception (see Frommlet et al ., ). The multifaceted relationship of bacteria and phytoplankton spans from being ecologically cooperative to competitive (Amin et al ., ).…”

“…vitamin B 12 ; Amin et al ., ), while also competing with Symbiodiniaceae for essential inorganic nutrients (Joint et al ., ). Symbiodiniaceae cultures contain abundant bacterial communities (Ritchie, ; Shoguchi et al ., ; Frommlet et al ., ; Lawson et al ., ), with less than 5% of Symbiodiniaceae in vitro studies to‐date working with axenic cultures (Lawson et al ., ). In fact, the recent study by Lawson et al .…”