title: Molecular genetic variation within and among isolates of QPX (Thraustochytridae), a parasite of the hard clam Mercenaria mercenaria.
abstract: The thraustochytrid known as QPX (Quahog Parasite Unknown) has sporadically caused disease in the hard clam Mercenaria mercenaria along the east coast of North America since the 1960s. We hypothesized that genetically distinct QPX strains might be responsible for outbreaks of QPX disease in different areas and tested this hypothesis by comparing several QPX isolates recovered from the recent outbreak in Raritan Bay, New York with QPX strains isolated from 2 outbreaks in Massachusetts, USA. There was no variation in small subunit rDNA (SSU rDNA), 5.8S rDNA, or 4 mitochondrial gene sequences. In contrast, both of the ribosomal ribonucleic acid (rRNA) operon intergenic spacers, internal transcribed spacers 1 and 2 (ITS1 and ITS2), revealed substantial sequence variation. However, strain-specific sequences were not detected because the ITS sequence variation within QPX isolates was comparable to the variation between isolates. ITS1 sequences recovered from an infected clam by amplification with a QPX ITS2-specific primer were identical to those recovered from the QPX isolates.
authors.affiliation: Marine Sciences Research Center, Stony Brook University, Stony Brook, New York 11794-5000, USA.
authors.forename: Hua
authors.initials: H
authors.lastname: Qian
authors.forename: Qianqian
authors.initials: Q
authors.lastname: Liu
authors.forename: Bassem
authors.initials: B
authors.lastname: Allam
authors.forename: Jackie L
authors.initials: JL
authors.lastname: Collier
mesh_terms: D000818:Animals; D001483:Base Sequence; D017931:DNA Primers / Q000737:chemistry; D016054:DNA, Protozoan / Q000737:chemistry; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D021903:DNA, Ribosomal Spacer / Q000737:chemistry / Q000235:genetics; D056890:Eukaryota / Q000235:genetics* / Q000302:isolation & purification / Q000472:pathogenicity*; D050259:Genes, Mitochondrial / Q000235:genetics; D014644:Genetic Variation; D049891:Mercenaria / Q000469:parasitology*; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D010802:Phylogeny; D016133:Polymerase Chain Reaction / Q000662:veterinary; D016415:Sequence Alignment
chemical_list: D017931:DNA Primers; D016054:DNA, Protozoan; D004275:DNA, Ribosomal; D021903:DNA, Ribosomal Spacer