Abstract
We have developed a simple and sensitive method to detect microbial respiration at subzero temperatures. Microbial activity was detected by measuring 14CO 2 evolved during the microbial-mediated mineralization of [1- 14C] acetic acid or [2- 14C] glucose in microcosm assays using modified 14CO 2 traps. Various 14CO 2 traps, designed to withstand freezing at subzero temperatures, were tested for their quench characteristics during liquid scintillation spectrometry and their ability to trap 14CO 2. Solutions consisting of 1 M KOH supplemented with 20% or 30% v/v ethylene glycol did not freeze at temperatures above − 20 °C and had a minor quenching effect on liquid scintillation spectrometry. Addition of ethylene glycol did have an effect on the efficiency of 14CO 2 trapping, as the cumulative recovery of 14CO 2 was reduced by 14% and 32% in the 1 M KOH + 20% ethylene glycol and 1 M KOH + 30% ethylene glycol solutions, respectively. Using the modified 14CO 2 traps, microbial activity in representative Canadian high Arctic environmental samples was detected at temperatures as low as − 15 °C. This simple method allows for sensitive, specific, and reliable detection of microbial activity occurring at subzero temperatures and is readily adaptable for studies in other cryoenvironments.
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