Carbon isotopic fractionation in lipids from methanotrophic bacteria: Relevance for interpretation of the geochemical record of biomarkers

Changing redox conditions at cold seeps as revealed by authigenic carbonates from Alaminos Canyon, northern Gulf of Mexico

“…Moreover, the various types of cultured methanotrophs use different carbon assimilation pathways (see Hanson and Hanson, 1996 for a review). Type I methanotrophs use the ribulose monophosphate (RuMP) carbon assimilation pathway, whereas Type II methanotrophs use the serine pathway (Summons et al, 1994;Hanson and Hanson, 1996;Jahnke et al, 1999). Type X methanotrophs use the RuMP pathway as well as the Rubisco and serine pathways (Jahnke et al, 1999).…”

“…The major difference of the various assimilation pathways of Type I/X and Type II results in significant differences in carbon isotope fractionation between the carbon source and the lipids synthesized, with a greater fractionating in Type I and X methanotrophs (cf. Summons et al, 1994;Jahnke et al, 1999). While 4α-methylcholesta-8(14),24-dien-3β-ol suggests the former presence of methanotrophic bacteria of Type I/X, the BHPs aminotetrol and aminotriol suggest the presence of Type II methanotrophs.…”

“…Compoundspecific carbon isotopes may allow a further discrimination (cf. Summons et al, 1994;Jahnke et al, 1999).…”

“…However, the presence of 4α-methylcholesta-8(14),24-dien-3β-ol, its isotopic signature, and Δδ 13 C value are puzzling. So far, this sterol has been used as biomarker of Type X methanotrophs (e.g., Bouvier et al, 1976;Summons et al, 1994;Schouten et al, 2000). The biomarker inventory of endosymbiotic, marine methanotrophs harbored in mussel gills from the GoM resembles the pattern of Type II methanotrophs found in AC 645 carbonates (cf.…”

Identification and quantification of polyfunctionalized hopanoids by high temperature gas chromatography–mass spectrometry

“…In modern sediments, functionalized BHPs are being explored as diagnostic for varying clades of bacteria (reviewed by ).In rocks and oils,the relative abundance of different hopane isomers can provide information about both environmental conditions during deposition, as well as maturity (Seifert and Moldowan, 1980;Brassell et al, 1983;Peters and Moldowan, 1991;Peters et al, 2005). For ancient rocks, hopanoids methylated at C-2 or C-3 have received particular attention because they have been proposed as diagnostic markers for cyanobacteria and aerobic methylotrophs, respectively (Zundel and Rohmer, 1985a,b;Summons and Jahnke, 1990;Summons et al, 1994Summons et al, , 1999Farrimond et al, 2004).A current research focus lies in understanding the cellular function of BHPs in bacteria, the genetic basis for their biosynthesis and modification, and their distribution and evolutionary relationships among extant organisms (Fischer et al, 2005;Blumenberg et al, 2006;Fischer and Pearson, 2007;Rashby et al, 2007;Doughty et al, 2009;Welander et al, 2009Welander et al, , 2010Welander et al, , 2012Bradley et al, 2010).…”