Deep subsurface sulfate reduction and methanogenesis in the Iberian Pyrite Belt revealed through geochemistry and molecular biomarkers.

The Iberian Pyrite Belt (IPB, southwest of Spain), the largest known massive sulfide deposit, fuels a rich chemolithotrophic microbial community in the Río Tinto area. However, the geomicrobiology of its deep subsurface is still unexplored. Herein, we report on the geochemistry and prokaryotic diversity in the subsurface (down to a depth of 166 m) of the Iberian Pyritic belt using an array of geochemical and complementary molecular ecology techniques. Using an antibody microarray, we detected polymeric biomarkers (lipoteichoic acids and peptidoglycan) from Gram-positive bacteria throughout the borehole. DNA microarray hybridization confirmed the presence of members of methane oxidizers, sulfate-reducers, metal and sulfur oxidizers, and methanogenic Euryarchaeota. DNA sequences from denitrifying and hydrogenotrophic bacteria were also identified. FISH hybridization revealed live bacterial clusters associated with microniches on mineral surfaces. These results, together with measures of the geochemical parameters in the borehole, allowed us to create a preliminary scheme of the biogeochemical processes that could be operating in the deep subsurface of the Iberian Pyrite Belt, including microbial metabolisms such as sulfate reduction, methanogenesis and anaerobic methane oxidation.

Localization of specific erythropoietin binding sites in defined areas of the mouse brain.

The main physiological regulator of erythropoiesis is the hematopoietic growth factor erythropoietin (EPO), which is induced in response to hypoxia. Binding of EPO to the EPO receptor (EPO-R), a member of the cytokine receptor superfamily, controls the terminal maturation of red blood cells. So far, EPO has been reported to act mainly on erythroid precursor cells. However, we have detected mRNA encoding both EPO and EPO-R in mouse brain by reverse transcription-PCR. Exposure to 0.1% carbon monoxide, a procedure that causes functional anemia, resulted in a 20-fold increase of EPO mRNA in mouse brain as quantified by competitive reverse transcription-PCR, whereas the EPO-R mRNA level was not influenced by hypoxia. Binding studies on mouse brain sections revealed defined binding sites for radioiodinated EPO in distinct brain areas. The specificity of EPO binding was assessed by homologous competition with an excess of unlabeled EPO and by using two monoclonal antibodies against human EPO, one inhibitory and the other noninhibitory for binding of EPO to EPO-R. Major EPO binding sites were observed in the hippocampus, capsula interna, cortex, and midbrain areas. Functional expression of the EPO-R and hypoxic upregulation of EPO suggest a role of EPO in the brain.