OCCURRENCE OF 3-HYDROXYALKANOIC ACIDS IN SEDIMENTS FROM THE GUAYMAS BASIN (GULF OF CALIFORNIA)

The Guaymas basin (Gulf of California) provides a particularly interes ting extreme environment. Temperatures ranged from 3 degrees C to 11 d egrees C at the organic-rich sediment surface and increased with depth , ranging from 59.7 degrees C to 150 degrees C from 20 cm to 30 cm. Af ter either acidic or alkaline hydrolysis of rock and sediment samples collected near active hydrothermal mounds, 3-hydroxyalkanoic acids hav e been detected by gas chromatography and gas chromatography-mass spec trometry with 3-hydroxyoctanoic and 3-hydroxydecanoic acids predominat ing. These acids appear to be of microbial origin, arising from the en dogenous storage polymers poly(3-hydroxyalkanoates). With respect to t he microbial community structure as previously determined from lipid b iomarkers, these 3-hydroxyalkanoic acids seem to be associated with ei ther anaerobic bacteria and/or type II methanotrophs. Conversely these polymers were not associated with Beggiota mats present on the surfac e of the sediments. The presence of 3-hydroxy-3-methylbutanoic acid in trace amounts as well as of 2-hydroxyoctanoic acid is reported. The o ccurrence of these hydroxyalkanoic acids raises interesting questions about their origin. (C) 1998 Published by Elsevier Science B.V. All ri ghts reserved.