http://www.loc.gov/mods/v3 http://www.loc.gov/standards/mods/v3/mods-3-2.xsd
Lipid biogeochemistry of Gulf of Mexico hydrocarbon seep communities
Despite the fact that symbiotic processes between seep invertebrates and symbiotic bacteria are well documented by enzymatic and electron microscopic studies, little is known of the biochemical interactions between the host animals and their endosymbionts. This study couples detailed molecular analyses with com pound-specific isotope analyses (CSLA) to characterize biomarker distribution of seep organisms and thereby illustrate the symbiotic processes between seep invertebrates and associated bacteria. The composition of fatty acids, sterols and hopenes of hydrocarbon seep mytilids and vestimentiferan tube worms from the northern Gulf of Mexico was investigated. FATTY ACIDS: (1) Forty-four different C12-C24 fatty acids were found in the mussel-bacteria association. C16 saturated and monounsaturated fatty acids accounted for 50% of the total fatty acids. (2) Fatty acids were dominated by unsaturated fatty acids with high degree of unsaturation (up to five double bonds) and a variety of positional isomers. STEROLS AND HOPENES: (1) The total sterols were found to be from 1.95x10^3 to 5.35x10^3 μg/g. Individual sterols include lanosterol. 14-desmethyl lanosterol, 4a-methylzymosterol, lophenol, 4α-methyl-cholest-8-en-ol. 7- dehydrocholesterol, lathosterol, cholesterol, and cholestanol. (2) Hop-21-ene and hop-22(29)-ene (140 to 150|μg/g), and trace amount of squalene were found in the mussel-bacteria association. δ13C OF FATTY ACIDS: (1) The individual fatty acids of the mytilid mussels have δ13C values from -49.0 to -56.9[parts per thousand]. The fatty acids of the vestimentiferan tube worms are relatively enriched in 13C, ranging from -31.6%o to - 38.6[parts per thousand]. (2) The Δ values (δ13C[fatty acids] - δ13C[tissue], weighted average) are from -1.2[parts per thousand] and -4.8[parts per thousand] mytilids, and +3.9[parts per thousand] (tube worms). The predominance of C16 saturated and monounsaturated fatty acids, the presence of abundant 4-methyl sterol and hopene, and the the light δ13C values of mussel tissue and fatty acids all indicate the overwhelming importance of methanotrophs in the nutrition of the seep mussels in the deep sea. From the δ13C of vestimentiferan tissue and fatty acids, a C4 -plant type biosynthetic pathway was inferred.