Bacteriohopanepolyol signatures of bacterial populations in Western Canadian soils

Abstract

Bacteriohopanepolyols (BHPs) are naturally occurring compounds derived from bacteria. Their quantity and diversity in five Western Canadian soils, which vary mostly in vegetative cover, were examined using high performance liquid chromatography – atmospheric pressure chemical ionization – mass spectrometry (HPLC–APCI–MS). Eighteen BHP compounds including tetra-, penta- and hexa-functionalised components, as well as composite components, were identified. Concentrations were highest in the forest-grassland transition soil [515μg/g organic carbon (OC)], followed by the forest soil (431μg/g OC) and the grassland soils (333–306μg/g OC). The distribution trends measured using HPLC–ACPI–MS agree with hopanoid measurements using gas chromatography–mass spectrometry (GC–MS) but intact BHPs were detected at a concentration that was an order of magnitude higher using HPLC–APCI–MS. Adenosylhopane was the most abundant BHP in all the samples and comprised on average 27% of total BHPs, supporting earlier work indicating that adenosylhopane is an excellent soil-specific biomarker. The soil samples vary in vegetative cover and this is likely one of the main reasons for observing variation in BHP composition, suggesting that BHP biomarkers may be a valuable tool for assessing bacterial community structure in soil when used in cooperation with other molecular microbial ecology methods (such as DNA genotyping).