title: Molecular quantification of symbiotic dinoflagellate algae of the genus Symbiodinium.
abstract: The dinoflagellate microalga Symbiodinium is the dominant algal symbiont in corals and related marine animals. To explore the incidence of mixed infections, methods employing real-time quantitative polymerase chain reaction (QPCR) and fluorescence in situ hybridization (FISH) were developed. In experiments focusing on Symbiodinium clades A and B, QPCR and FISH results were well correlated and generally more precise and sensitive than those from the endpoint PCR-restriction fragment length polymorphism analysis (PCR-RFLP) traditionally used for this application, thus increasing the detected incidence of mixed infections. For example, the prevalence of mixed infections in the sea anemone Condylactis gigantea was 40% by PCR-RFLP and 80%-90% by QPCR and FISH. However, the use of QPCR and FISH was limited by inter-host variation in the rRNA gene copy number per Symbiodinium cell, precluding any single conversion factor between QPCR signal and Symbiodinium cell number; and one FISH probe that gave excellent hybridization efficiency with cultured Symbiodinium yielded variable results with Symbiodinium from symbioses. After controlling for these caveats, QPCR studies revealed that field-collected hosts previously described as universally unialgal bore up to 1.6% of the alternative clade. Further research is required to establish the contribution that algal cells at low density in symbiosis and external to the symbiosis make to the minor clade.
authors.affiliation: Department of Biology, University of York, York, YO10 5YW, UK.
authors.forename: Jeannette E
authors.initials: JE
authors.lastname: Loram
authors.forename: Neil
authors.initials: N
authors.lastname: Boonham
authors.forename: Peter
authors.initials: P
authors.lastname: O'Toole
authors.forename: Henry G
authors.initials: HG
authors.lastname: Trapido-Rosenthal
authors.forename: Angela E
authors.initials: AE
authors.lastname: Douglas
mesh_terms: D000818:Animals; D004141:Dinoflagellida / Q000145:classification* / Q000235:genetics / Q000502:physiology; D014644:Genetic Variation; D017404:In Situ Hybridization, Fluorescence; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D012615:Sea Anemones / Q000502:physiology; D013559:Symbiosis