TY - JOUR
T1 - Enumeration of parasitic chytrid zoospores in the Columbia River via quantitative PCR
AU - Maier, Michelle A.
AU - Peterson, Tawnya D.
N1 - Publisher Copyright:
© 2016, American Society for Microbiology. All Rights Reserved.
PY - 2016
Y1 - 2016
N2 - Through lethal infection, fungal parasites of phytoplankton ("chytrids") repackage organic material from the large, effectively inedible, colonial diatoms they infect into much smaller zoospores, which are easier for zooplankton to consume. However, their small size and lack of distinguishing morphological features render it difficult to distinguish zoospores from other small flagellates in mixed assemblages in the natural environment. In this study, we developed and tested a method to quantify chytrid zoospores in field studies using quantitative PCR (qPCR) targeting the internal transcribed spacer 2 (ITS2) region within the rRNA gene cluster. To achieve accurate quantification, the assay was designed to be highly specific for a parasite (Rhizophydium planktonicum) of the diatom Asterionella formosa; however, the approach is applicable to additional host-parasite systems. Parasitic zoospores were detected and quantified in the freshwater reaches of the lower Columbia River, as well as in the salt-influenced estuary and river plume. The coincidence between zoospore abundances and a prevalence of small zooplankton during blooms of large, colonial diatoms in the spring suggests that Columbia River zooplankton may be poised to benefit nutritionally from chytrid zoospores, thus providing a mechanism to retain organic carbon within the system and reduce losses to downstream export. We estimate that~15% of the carbon biomass tied up in blooms of the dominant diatom species is transformed into zoospores through the parasitic shunt during spring.
AB - Through lethal infection, fungal parasites of phytoplankton ("chytrids") repackage organic material from the large, effectively inedible, colonial diatoms they infect into much smaller zoospores, which are easier for zooplankton to consume. However, their small size and lack of distinguishing morphological features render it difficult to distinguish zoospores from other small flagellates in mixed assemblages in the natural environment. In this study, we developed and tested a method to quantify chytrid zoospores in field studies using quantitative PCR (qPCR) targeting the internal transcribed spacer 2 (ITS2) region within the rRNA gene cluster. To achieve accurate quantification, the assay was designed to be highly specific for a parasite (Rhizophydium planktonicum) of the diatom Asterionella formosa; however, the approach is applicable to additional host-parasite systems. Parasitic zoospores were detected and quantified in the freshwater reaches of the lower Columbia River, as well as in the salt-influenced estuary and river plume. The coincidence between zoospore abundances and a prevalence of small zooplankton during blooms of large, colonial diatoms in the spring suggests that Columbia River zooplankton may be poised to benefit nutritionally from chytrid zoospores, thus providing a mechanism to retain organic carbon within the system and reduce losses to downstream export. We estimate that~15% of the carbon biomass tied up in blooms of the dominant diatom species is transformed into zoospores through the parasitic shunt during spring.
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U2 - 10.1128/AEM.00084-16
DO - 10.1128/AEM.00084-16
M3 - Article
C2 - 27107109
AN - SCOPUS:84976408103
SN - 0099-2240
VL - 82
SP - 3857
EP - 3867
JO - Applied and Environmental Microbiology
JF - Applied and Environmental Microbiology
IS - 13
ER -