Patterns of metabolic partitioning among extreme temperatures
We observed different partitioning patterns of metabolic diversity according to environmental temperatures (Figure 4). The fumarole with the highest temperature (98 oC) exhibited metabolic potential significantly higher for functions associated with sulfate reduction (p < 0.001), dissimilatory nitrite reduction (p < 0.001) and carbon dioxide fixation (p< 0.001) when compared to other fumaroles and glaciers. Although sulfur metabolism was abundant among all temperatures, different metabolic pathways related to sulfur were observed according to the temperature. While sulfate reduction was prevalent in the highest temperature fumarole, a high number of genes related to inorganic sulfur assimilation (p < 0.001) and sulfur oxidation (pvalue was not significant, p < 0.1) were detected in <80 oC fumaroles. In general, nitrogen metabolism was dominant in <80 oC fumaroles when compared to other samples, with nitrate and nitrite ammonification (p < 0.02), denitrification (p < 0.01), nitrogen fixation (p < 0.05) and ammonia assimilation (p < 0.001) as the prevalent metabolic nitrogen pathways. All fumaroles showed a similar abundance of genes belonging to sulfur oxidation, nitrate and nitrite ammonification, and dissimilatory nitrite reduction. The genetic potential for carbon fixation was much higher in the 98 oC fumarole (p < 0.01), whereas photosynthesis was mainly detected in the <80 oC fumaroles and glaciers. In glaciers, the genes identified within carbon metabolism were mainly associated with heterotrophy and central carbon pathways, such as the pentose phosphate pathway and glycolysis, as were respiration and fermentation. The function of carbon storage regulators was significantly higher in <80 oC fumaroles, in addition to the observation of other carbon-related processes, such as photosynthesis, fermentation, and carbon fixation (Figure 4).