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Project Progress

Rio Tinto: Spain’s Acidic/High Metal Extreme Environment (dm)

We have completed an analysis of full-length, eukaryotic, small-subunit ribosomal RNA molecular characterization of several sampling stations along the Tinto River, including samples taken at the source of the river. Some of our clones showed high similarity to taxa reported in previous studies employing light-microscopical techniques. These included the highly conspicuous members of the Euglenozoa (euglenids), Chlorophyta (chlamydomonad and chlorella-like relatives), as well as the Bacillariophyta (diatoms). Members of the Viridiplantae were represented by streptophyte and charophyte relatives.

However, our results also revealed a diversity of other protists not previously identified with conventional technologies. These included members of the stramenopiles (e.g. chrysophytes) and several cercomonad relatives. Among the most interesting clone sequences in the river were those from relatives of amoeboid taxa. In our molecular survey, we found one clone that branched with the Vahlkampfia. Occurrence of vahlkampfids has been noted in other acidic environments. More interestingly, a few of our clones branched with other recently sequenced amoeboid taxa. In initial analyses, these clones branched near the animal/fungal divergence. To obtain a more fully resolved phylogenetic placement for these clones, we added them to a data set with fewer taxa (19) wherein additional sites could be used in the analysis (1550). Our more refined analyses showed these clones branching among the nucleariid amoebae â?? a group of filose amoebae branching near the animal-fungal divergence and of questionable monophyly. The second group of clones branched with Filamoeba nolandi. The current taxonomic placement of Filamoeba nolandi is equivocal and reflects much of the state of amoebae systematics.

Our study also revealed a diversity of fungi somewhat different than those previously identified in the river using traditional methods. The majority of our clones belonged to the Ascomycota, but there were a few representatives from the Zygomycota. We have summarized our results in a phylogenetic analysis.