26. IN SEARCH OF A SUBSURFACE BIOSPHERE AT A SLOW-SPREADING RIDGE¹

A.-L. Reysenbach,² N.G. Holm,³ K. Hershberger,⁴ D. Prieur,⁵ and C. Jeanthon⁵

ABSTRACT

Microbiological and molecular examination of cores from the Trans-Atlantic Geotraverse (TAG) hydrothermal field (Leg 158) indicated that, in the samples analyzed and within the detection limits of the methods used, there was no significant microbial biomass that could be indicative of deep subsurface biological communities at this site. Two samples from the upper 100 cm of core produced enrichment cultures of hyperthermophilic sulfur-reducing microorganisms. However, the possibility that these organisms were entrained from the surface of the hydrothermal field during coring cannot be ruled out. It was concluded that, although an extensive subsurface biosphere might exist elsewhere at TAG, no conclusive evidence for such an environment was obtained from the samples analyzed during Leg 158 and the challenge to explore this tantalizing hypothesis remains open.

¹Herzig, P.M., Humphris, S.E., Miller, D.J., and Zierenberg, R.A. (Eds.), 1998. Proc. ODP, Sci. Results, 158: College Station, TX (Ocean Drilling Program).
²Department of Biochemistry and Microbiology, Cook Campus, Rutgers University, New Brunswick, NJ 08903, U.S.A. alr@imcs.rutgers.edu
³Department of Geology and Geochemistry, Stockholm University, S-106 91 Stock-holm, Sweden.
⁴Biology Department, Indiana University, Bloomington, IN 47405, U.S.A.
⁵Station Biologique, B. P. 74, F-29682 Roscoff cedex, France.