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Project Progress

As part of our Microbial diversity and population structure studies in the Río Tinto , we have carried out two full sampling efforts, in the fall of 2003 and in January of 2004, corresponding to the dry and wet season extremes. We have chosen our stations based on varying concentrations and oxidation state of iron present (see http://astrobiology.mbl.edu/riotinto/ for more detailed information and photographs of the study locations). For each station we have sampled three different sites, with three-fold replication. For each sample, we filtered 2 L of water for DNA extraction and concomitantly collected physico-chemical parameters consisting of in situ (pH, oxygen, redox, temperature and conductivity) and ex situ (S, Fe, Zn, Cu, Al, As, Ni, Mg, Ca, K, etc.) measurements, and preserved formalin samples for bacterial and protist enumeration. To date, all DNA has been extracted and physico-chemical measurements completed. We plan to use these DNA samples to both build rDNA clone libraries and conduct a three-domain serial analysis of ribosomal sequence tags (3D-SARST) analysis for the three domains of life.

We are currently analyzing the results of both clone library sequences and serial analysis of V6 ribosomal sequence tags (SARST-V6) hypervariable region— a region spanning from 52-152 base pairs in length in known bacteria) experiments on samples collected during a pilot project conducted in October of 2002. We have built bacterial, archaeal and eukaryal clone libraries for one sample from each station. Over seventy unique clones were fully sequenced and used in a three-domain phylogenetic analysis consisting of 300 total taxa. Over 4,000 SARST sequenced tags have also been recovered and used in calculating alpha and beta diversity indices. The SARST diversity data will be combined with the physico-chemical parameters in analyses that will reveal important aspects of the biogeochemistry of this extreme environment. We will summarize these data in a review paper of the diversity in the river and other publications focusing on the microbial ecology to be submitted later this year.