Detection of Archaeal Diether Lipid by Gas Chromatography from Humus and Peat
A suitable method based on gas chromatography to detect the diphytanylglycerol diether (archaeol), the domain membrane lipid of Archaea, was used to trace the presence of Archaea in humus and peat. The elution of the standard used (1,2-di-O-hexadecyl-rac-glycerol) was reproducible above a concentration of 1 mg l-1 (2 ng peak-1), which was the detection limit of the method. No archaeol was detected from the humus sample. This was verified using polymerase chain reaction (PCR) with primers specific to archaeal 16S rDNA gene region. Spiking the humus with an archaeon, Halobacterium salinarum, gave a positive response for both methods. This indicated that there were no Archaea in the specific humus sample. The peat samples used for extraction of diether lipids were first characterized for their CH4 production rate, which indicated the presence of methanogens (Archaea). With unlimited access to CO2/H2, the methane production rate peaked between 15 and 25 cm. The archaeol could be identified from all depths sampled. The maximum archaeol concentration was at 20 cm, indicating the highest methanogenic population density at this depth. This is in accordance with the results from the methane production estimates.