Qian Hua, Liu Qianqian, Allam Bassem, Collier Jackie L
Marine Sciences Research Center, Stony Brook University, Stony Brook, New York 11794-5000, USA.
Dis Aquat Organ. 2007 Sep 14;77(2):159-68. doi: 10.3354/dao01848.
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.
自20世纪60年代以来，被称为QPX（圆蛤寄生虫未知物）的破囊壶菌偶尔会在北美东海岸的硬壳蛤（Mercenaria mercenaria）中引发疾病。我们推测，基因上不同的QPX菌株可能是不同地区QPX疾病爆发的原因，并通过将从纽约拉里坦湾最近一次疫情中分离出的几种QPX菌株与从美国马萨诸塞州的两次疫情中分离出的QPX菌株进行比较，来检验这一假设。小亚基核糖体DNA（SSU rDNA）、5.8S rDNA或4个线粒体基因序列没有差异。相比之下，两个核糖体核糖核酸（rRNA）操纵子基因间隔区，即内部转录间隔区1和2（ITS1和ITS2），都显示出大量的序列变异。然而，由于QPX分离株内部的ITS序列变异与分离株之间的变异相当，因此未检测到菌株特异性序列。通过用QPX ITS2特异性引物扩增从受感染蛤中回收的ITS1序列，与从QPX分离株中回收的序列相同。
