Lipid composition of the microbial mat from a hypersaline environment (Vermelha Lagoon, Rio de Janeiro, Brazil)

ABSTRACT This study determines organic-matter (OM) composition in the different color layers of a stratified hypersaline microbial mat and verifies hypothesis that each layer includes distinct group lipids. The relation precursor lipids from to hydrocarbon fossil records was also evaluated. To end, studied glycolipids (GLs), phospholipids (PLs), “neutral” (NLs, including hydrocarbons, n-alkanols, sterols, hopanols, free fatty acids, wax esters) four (A–D; depth intervals: up 0.5 cm, 0.5–1.0 1.5–3.0 3.0–6.0 respectively) Vermelha Lagoon, Rio de Janeiro, Brazil. Microscopic characterization revealed presence 16 cyanobacterial morphospecies, with predominance Microcoleus chthonoplastes. notable prevalence saturated straight-chain acids (FAs), n-16:0 n-18:0 their monounsaturated counterparts, n-16:1 n-18:1 all three lipid fractions (GLs, PLs, NLs), associated domination n-C17 alkane n-C17:1 alkene among hydrocarbons confirmed main imprint cyanobacteria. classes implies contribution sulfate-reducing bacteria such as Desulfomicrobium sp. strain, purple sulfur bacteria, well possible input Geobacter spp. Desulfovibrio spp., particularly deeper layers. decrease total extractable (TELs) yield A D indicates synthesis is far more intense by photosynthesizing cyanobacteria than anaerobic microorganisms. content PLs uniform low (< 5%) layers, implying extremely quick degradation. GLs, followed NLs, were most abundant indicating medium, which characterized carbon source excess limited nitrogen source, regulates microorganism growth. upper (green) B (reddish-brown) differ those lower, C (dark brown greenish) (brown) according NLs/GLs ratio, higher former. compositions reveal distinctions between individual mat. observed clearly amount high-molecular-weight (C22–C31) n-alkanes long-chain (C21–C30) phytol, bishomohopanol, tetrahymanol, C27–C29 stanol/stenol ratio neutral fraction, branched (iso anteiso) FAs w9/w7 FA GLs fraction. mentioned parameters imply greater B, impact photosynthetic red algae elevated marine ciliate species, feeding on C, increment anoxygenic phototrophic heterotrophic D. greatest capability for B. showed significant relationship important biomarkers' fingerprints rocks extracts petroleum derived carbonate environments, distribution n-alkanes, high abundance phytane gammacerane, regular steranes. Therefore, these results offer an insight into transformation OM during sedimentation processes environment its record.