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Molecular and lipid biomarker analysis of a gypsum‐hosted endoevaporitic microbial community
Author(s) -
Jahnke L. L.,
TurkKubo K. A.,
N. Parenteau M.,
Green S. J.,
Kubo M. D.Y.,
Vogel M.,
Summons R. E.,
Des Marais D. J.
Publication year - 2014
Publication title -
geobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.859
H-Index - 72
eISSN - 1472-4669
pISSN - 1472-4677
DOI - 10.1111/gbi.12068
Subject(s) - anoxic waters , biology , microbial population biology , hopanoids , botany , phylogenetic tree , microbial mat , biomarker , environmental chemistry , chemistry , ecology , gene , bacteria , biochemistry , cyanobacteria , genetics , paleontology , structural basin , source rock
Abstract Modern evaporitic microbial ecosystems are important analogs for understanding the record of earliest life on E arth. Although mineral‐depositing shallow‐marine environments were prevalent during the P recambrian, few such environments are now available today for study. We investigated the molecular and lipid biomarker composition of an endoevaporitic gypsarenite microbial mat community in G uerrero N egro, M exico. The 16 S ribosomal RNA gene‐based phylogenetic analyses of this mat corroborate prior observations indicating that characteristic layered microbial communities colonize gypsum deposits world‐wide despite considerable textural and morphological variability. Membrane fatty acid analysis of the surface tan/orange and lower green mat crust layers indicated cell densities of 1.6 × 10 9 and 4.2 × 10 9 cells cm −3 , respectively. Several biomarker fatty acids, ∆7,10‐hexadecadienoic, iso ‐heptadecenoic, 10‐methylhexadecanoic, and a ∆12‐methyloctadecenoic, correlated well with distributions of E uhalothece , S tenotrophomonas , D esulfohalobium , and R hodobacterales , respectively, revealed by the phylogenetic analyses. Chlorophyll ( C hl) a and cyanobacterial phylotypes were present at all depths in the mat. Bacteriochlorophyl ( B chl) a and B chl c were first detected in the oxic‐anoxic transition zone and increased with depth. A series of monomethylalkanes ( MMA ), 8‐methylhexadecane, 8‐methylheptadecane, and 9‐methyloctadecane were present in the surface crust but increased in abundance in the lower anoxic layers. The MMA structures are similar to those identified previously in cultures of the marine C hloroflexus ‐like organism ‘ C andidatus C hlorothrix halophila’ gen. nov., sp. nov., and may represent the B chl c community. Novel 3‐methylhopanoids were identified in cultures of marine purple non‐sulfur bacteria and serve as a probable biomarker for this group in the lower anoxic purple and olive‐black layers. Together microbial culture and environmental analyses support novel sources for lipid biomarkers in gypsum crust mats.