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).