title: A thraustochytrid protist isolated from Mercenaria mercenaria: molecular characterization and host defense responses.
abstract: A previously undescribed thraustochytrid protist, designated C9G, was isolated from the gills of a clam, Mercenaria mercenaria, collected from the Bay of Fundy, Canada. Sequence data analysis showed C9G to be related to the clam pathogen QPX, quahog parasite unknown; however, it is not enveloped by secreted mucoid material as is the case for QPX. Clam hemocytes recognized and phagocytized C9G in vitro in the absence of plasma recognition factors. Hemocytes were also capable of killing ingested C9G, as shown by the use of a tetrazolium reduction viability assay. The mechanisms underlying intracellular antimicrobial activity are not yet established, but no detectable cytotoxic reactive oxygen species were generated during phagocytosis of C9G. Clam plasma proteins were shown to inhibit C9G growth at concentrations similar to those in unfractionated hemolymph.
authors.affiliation: Chesapeake Biological Laboratory, University of Maryland Center for Environmental Science, P.O. Box 38, Solomons, MD 20688, USA. anderson@cbl.umces.edu
authors.forename: Robert S
authors.initials: RS
authors.lastname: Anderson
authors.forename: Brenda S
authors.initials: BS
authors.lastname: Kraus
authors.forename: Sharon E
authors.initials: SE
authors.lastname: McGladdery
authors.forename: Kimberly S
authors.initials: KS
authors.lastname: Reece
authors.forename: Nancy A
authors.initials: NA
authors.lastname: Stokes
mesh_terms: D000818:Animals; D001483:Base Sequence; D049872:Bivalvia / Q000276:immunology* / Q000469:parasitology*; D004275:DNA, Ribosomal / Q000235:genetics; D056890:Eukaryota / Q000235:genetics* / Q000302:isolation & purification*; D006434:Hemocytes / Q000276:immunology*; D066298:In Vitro Techniques; D008163:Luminescent Measurements; D008969:Molecular Sequence Data; D009580:Nitroblue Tetrazolium / Q000378:metabolism; D009674:Nova Scotia; D010587:Phagocytosis / Q000276:immunology; D010802:Phylogeny; D017382:Reactive Oxygen Species
chemical_list: D004275:DNA, Ribosomal; D017382:Reactive Oxygen Species; D009580:Nitroblue Tetrazolium