Humboldt's spa: microbial diversity is controlled by temperature in geothermal environments

Area of Science:

• Microbial Ecology
• Geothermal Microbiology
• Biogeography

Background:

• Alexander von Humboldt observed a latitudinal diversity gradient for plants and animals, linked to temperature.
• Previous studies indicated a weak or absent temperature-diversity gradient for Bacteria and Archaea.
• Geothermal environments offer unique conditions to study microbial diversity across extreme temperature and pH ranges.

Purpose of the Study:

• To investigate the impact of temperature and pH on bacterial and archaeal diversity.
• To determine the relationship between environmental factors and microbial community composition in geothermal areas.
• To assess whether temperature or pH is a stronger driver of microbial diversity in these unique ecosystems.

Main Methods:

• Pyrotag sequencing of 16S rRNA genes from 165 soil, sediment, and biomat samples.
• Analysis of samples from 36 geothermal areas in Canada and New Zealand.
• Examination of a wide temperature range (7.5–99°C) and pH range (1.8–9.0).

Main Results:

• Microbial species richness and diversity indices showed a strong correlation with temperature (R² up to 0.62).
• Diversity peaked at 24°C, decreasing at both higher and lower temperature extremes, indicating a unimodal distribution.
• While pH had a significant effect, temperature explained more variability (13–20%) in geothermal samples compared to previous soil studies.

Conclusions:

• Temperature is a primary factor controlling microbial diversity in geothermal environments across a broad thermal spectrum.
• The study demonstrates a significant temperature-diversity gradient for Bacteria and Archaea, contrary to some prior research.
• Findings highlight the critical role of temperature in shaping microbial communities in extreme habitats.