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Identification of Methanotrophic Biomarker Lipids in the Symbiont-Containing Gills of Seep MusselsMussels collected from hydrocarbon seeps in the Gulf of Mexico grow with methane as sole carbon and energy source due to a symbiotic association with methane-oxidizing bacteria. Transmission electron micrographs of mussel gills show cells with stacked intracytoplasmic membranes similar to type I methanotrophic bacteria. Methanotrophs are known to synthesize several types of cyclic triterpenes, hopanoids and methyl sterols, as well as unique monounsaturated fatty acid, double bond positional isomers that serve as biomarkers for this group. Lipid analysis of dissected mussels demonstrated the presence of these biomarkers predominantly in the gill tissue with much smaller amounts in mantle and remaining body tissues. Gill tissue contained 1150 micrograms/g dry wt. of hopanepolyol derivatives and diplopterol while the mantle tissue contained only 17 micrograms/g. The C16 monounsaturated fatty acids (16:1) characteristic of type I methanotrophic membranes dominated the gill tissue making up 53% of the total while only 5% 16:1 was present in the mantle tissue. The methyl sterol distribution was more dispersed. The predominant sterol in all tissues was cholesterol with lesser amounts of other desmethyl and 4-methyl sterols. The gill and mantle tissues contained 3461 micrograms (17% methyl) and 2750 micrograms (5% methyl) sterol per gm dry wt., respectively. Methyl sterol accounted for 44% of the sterol esters isolated from the gill, suggesting active demethylation of the methanotrophic sterols in this tissue. The use of lipid biomarkers could provide an effective means for identifying host-symbiont relationships.
Document ID
20020014605
Acquisition Source
Ames Research Center
Document Type
Preprint (Draft being sent to journal)
Authors
Jahnke, L. L.
Zahiralis, K. D.
Klein, H. P.
Morrison, David
Date Acquired
August 20, 2013
Publication Date
January 1, 1994
Subject Category
Life Sciences (General)
Meeting Information
Meeting: American Society for Microbiology
Location: Las Vegas, NV
Country: United States
Start Date: May 23, 1994
End Date: May 27, 1994
Sponsors: American Society for Microbiology
Funding Number(s)
PROJECT: RTOP 185-52-32-01
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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