Diversity of microbial eukaryotes in deep sea chemosynthetic ecosystems illuminated by molecular techniques

Abstract

Chemosynthetic ecosystems found in deep sea hydrothermal vents and cold seeps rely on the biological conversion of carbon dioxide or methane into organic matter using the oxidation of hydrogen sulfide or methane as a source of energy, rather than sunlight as in photosynthesis. It is known that communities of chemosynthetic ecosystems include endemic animals, such as mussels, clams, and tubeworms, along with bacterial and archaeal primary producers oxidizing reduced chemical species that support the survival of these animals. On the other hand, microbial eukaryotes (i.e., protists and fungi) in chemosynthetic ecosystems have not been investigated as thoroughly as the animals and prokaryotes. Nevertheless, mainly based on molecular techniques such as Culture-Independent PCR and fluorescence in situ hybridization, it has become more clearly understood that a phylogenetically broad range of microbial eukaryotes occurs in chemosynthetic ecosystems and that these microbes play a significant role as grazers, decomposers, or parasites. Furthermore, the existence of novel microbial eukaryotes exclusively or mainly inhabiting chemosynthetic ecosystems has also been suggested, stimulating future studies on their evolution and physiology.