Diversity of the Microeukaryotic Community in Sulfide-Rich Zodletone Spring (Oklahoma)

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Abstract
The microeukaryotic community in Zodletone Spring, a predominantly anaerobic sulfide and sulfur-rich spring, was examined using an 18S rRNA gene cloning and sequencing approach. The majority of the 288 clones sequenced from three different locations at Zodletone Spring belonged to theStramenopiles,Alveolata, andFungi, with members of the phylumCercozoa, orderDiplomonadida, and familyJakobidaerepresenting a minor fraction of the clone library. No sequences suggesting the presence of novel kingdom level diversity were detected in any of the three libraries. A large fraction of stramenopile clones encountered were monophyletic with either members of the genusCafeteria(orderBicosoecida) or members of the orderLabyrinthulida(slime nets), both of which have so far been encountered mainly in marine habitats. The majority of the observed fungal clone sequences belonged to the ascomycetous yeasts (orderSaccharomycetales), were closely related to yeast genera within theHymenobasidiomycetes(phylumBasidiomycetes), or formed a novel fungal lineage with several previously published or database-deposited clones. To determine whether the unexpected abundance of fungal sequences in Zodletone Spring clone libraries represents a general pattern in anaerobic habitats, we generated three clone libraries from three different anaerobic settings (anaerobic sewage digester, pond sediment, and hydrocarbon-exposed aquifer sediments) and partially sequenced 210 of these clones. Phylogenetic analysis indicated that clone sequences belonging to the kingdomFungirepresent a significant fraction of all three clone libraries, an observation confirmed by phospholipid fatty acid and ergosterol analysis. Overall, this work reveals an unexpected abundance ofFungiin anaerobic habitats, describes a novel, yet-uncultured group ofFungithat appears to be widespread in anaerobic habitats, and indicates that several of the previously considered marine protists could also occur in nonmarine habitats.