Mesophilic mineral-weathering bacteria inhabit the critical-zone of a perennially cold basaltic environment

• Published in: Geomicrobiology Journal
• Main Authors: Summers, Stephen, Thomson, Bruce C., Whiteley, Andrew, Cockell, Charles S.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: 2016
• Subjects: Iceland
• Online Access: https://oro.open.ac.uk/43257/; https://oro.open.ac.uk/43257/1/Summers%20et%20al%202015.pdf; https://doi.org/10.1080/01490451.2015.1039672

The weathering of silicate in the world’s critical-zone (rock-soil interface) is a natural mechanism providing a feedback on atmospheric CO2 concentrations through the carbonate-silicate cycle. We examined culturable bacterial communities from a critical-zone in western Iceland to determine the optimum growth temperature, ability to solubilise phosphate-containing minerals, which are abundant within the critical-zone area examined here. The majority of isolated bacteria were able to solubilize mineral-state phosphate. Almost all bacterial isolates were mesophilic (growth optima of 20-45°C), despite critical-zone temperatures that were continuously below 15°C, although all isolates could grow at temperatures associated with the critical-zone (-2.8 – 13.1°C). Only three isolates were shown to have thermal optima for growth that were within temperatures experienced at the critical-zone. These findings show that the bacteria that inhabit the western Icelandic critical-zone have temperature growth optima suboptimally adapted to their environment, implying that other adaptations may be more important for their long-term persistence in this environment. Moreover, our study showed that the cold basaltic critical-zone is a region of active phosphate mineral-weathering.