Oligonucleotide probes for the identification of three algal groups by dotblot and fluorescent whole-cell hybridization

Photosynthetic pico- and nanoplankton dominate phytoplankton biomass and pr imary production in the oligotrophic open ocean. Species composition, commu nity structure, and dynamics of the eukaryotic components of these size cla sses are poorly known primarily because of the difficulties associated with their preservation and identification. Molecular techniques utilizing 18S rRNA sequences offer a number of new and rapid means of identifying the pic oplankton. From the available 18S rRNA sequence data for the algae, we desi gned new group-specific oligonucleotide probes for the division Chlorophyta , the division Haptophyta, and the class Pelagophyceae (division Heterokont a). Dot blot hybridization with polymerase chain reaction amplified target rDNA and whole-cell hybridization assays with fluorescence microscopy and f low cytometry were used to demonstrate probe specificity. Hybridization res ults with representatives from seven algal classes supported the pylogeneti c affinities of the cells. Such group- or taxon-specific probes which are t hought to be the dominant algal taxa in the oligotrophic regions of the oce an.