Fluorescence In Situ Hybridization of Uncultured Zoosporic Fungi

Abstract

Recently, molecular environmental surveys of the eukaryotic microbial community in lakes have revealed a high diversity of sequences belonging to uncultured zoosporic fungi. Although they are known as saprobes and algal parasites in freshwater systems, zoosporic fungi have been neglected in microbial food web studies. Recently, it has been suggested that zoosporic fungi, via the consumption of their zoospores by zooplankters, could transfer energy from large inedible algae and particulate organic material to higher trophic levels. However, because of their small size and their lack of distinctive morphological features, traditional microscopy does not allow the detection of zoosporic organisms such as chytrids in the field. We have designed an oligonucleotidic probe specific to Chytridiales (i.e., the largest group of the true-fungal division of Chytridiomycota) and provide simplified step-by-step protocols for its application to natural samples using both the classical monolabeled-FISH and the CARD-FISH approaches, for the assessment of uncultured zoosporic fungi and other zoosporic microbial eukaryotes in natural samples.