Fluorescence in situ hybridization using 18S rRNA-targeted probe for specific detection of thraustochytrids (Labyrinthulomycetes)

Abstract

Thraustochytrids are cosmopolitan osmotrophic or heterotrophic microorganisms that play, especially in coastal ecosystems, important roles as decomposers and producers of polyunsaturated fatty acids (PUFA), and are also known to be pathogens of mollusks and seaweeds. However, because of shortcomings in the current methods for detection and enumeration of thraustochytrids, very little information is available concerning their natural dynamics and ecological roles. In this study, we propose a new method for detecting thraustochytrids using a fluorescent 18S ribosomal RNA (rRNA)-targeted oligonucleotide probe (Probe ThrFL1). Detection of thraustochytrids by means of the fluorescence in situ hybridization (FISH) technique with ThrFL1 was specific; the probe did not react with the other stramenopile organisms or with the dinoflagellate that was tested. Because of the high specificity and intense reactivity, the FISH protocol is expected to be a strong tool for examining ecological features of thraustochytrids.