Occurrence of highly abundant bacterial hopanoids in Dajiuhu peatland, central China

Based on gas chromatography and gas chromatography-mass spectrometry analyses, an amazing amount of hopanoids was detected in the peat deposits in the Dajiuhu National Wetland Park in central China. The hopanoids identified included hopanes (C₂₇-C₃₁ αβ, C₂₇-C₃₂ ββ, C₂₉ βα), hopenes (hop-22(29)-ene, 22,29,30-trinorhop-17(21)-ene, hop-17(21)-ene, hop-13(18)-ene, etc.), hopanoic acids (C₃₁-C₃₄ ββ, C₃₂-C₃₃ βα, C₃₂ αβ), hopanols (C₃₂ ββ and αβ) and hopanone (22,29,30-trinorhop-21-one). C₃₁ αβ-22R hopane was found to be the dominant hopanoid, more abundant than individual nalkanes derived from higher plants. These hopanoids, exclusive of some hopenes, are proposed to be primarily from bacteria. The dominant C₃₁ αβ-22R hopane in young sediments, without any thermal maturation, might be formed through microbial epimerization under acidic conditions in the peatland as suggested before, or directly from aerobic bacteria. This finding highlights the importance of microbes in the formation of peatland as well as in the reconstruction of paleoenvironments.