Phospholipid fatty acids were measured in samples of 60°-130°C sediment taken from three holes at Site 1036 (Ocean Drilling Program Leg 169) to determine microbial community structure and possible community replacement at high temperatures. Five of six samples had similar concentrations of phospholipid fatty acids (2-6 pmol/g dry weight of sediment), and biomass estimates from these measurements compare favorably with direct microscopic counts, lending support to previous microscopic measures of deep sedimentary biomass. Very long-chain phospholipid fatty acids (21 to 30 carbons) were detected in the sediment and were up to half the total phospholipid fatty acid measured; they appear to increase in abundance with temperature, but their significance is not known. Community composition from lipid analysis showed that samples contained standard eubacterial membrane lipids but no detectable archaeal lipids, though archaea would be expected to dominate the samples at high temperatures. Cluster analysis of Middle Valley phospholipid fatty acid compositions shows that lipids in Middle Valley sediment samples are similar to each other at all temperatures, with the exception of very long-chain fatty acids. The data neither support nor deny a shift to a high-temperature microbial community in hot cores, so at the present time we cannot draw conclusions about whether the microbes observed in these hot sediments are active.
1Summit, M., Peacock, A., Ringelberg, D., White, D.C., and Baross, J.A., 2000. Phospholipid fatty acid-derived microbial biomass and community dynamics in hot, hydrothermally influenced sediments from Middle Valley, Juan De Fuca Ridge. In Zierenberg, R.A., Fouquet, Y., Miller, D.J., Normark, W.R. (Eds.), Proc. ODP, Sci. Results, 169 [Online]. Available from World Wide Web: <http://www-odp.tamu.edu/publications/169_SR/chap_03/chap_03.htm>. [Cited YYYY-MM-DD]
2Oceanography Box 357940, University of Washington, Seattle WA 98195, USA. Correspondence author: summit@ocean.washington.edu
3Center for Environmental Biotechnology, University of Tennessee, 10515 Research Drive, Suite 300, Knoxville TN 37932-2575, USA
Date of initial receipt: 3 March 1999
Date of acceptance: 13 September 1999
Date of publication: 15 May 2000
Ms 169SR-117