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Applied and Environmental Microbiology, October 1998, p. 3869-3877, Vol. 64, No. 10
Departments of Plant and Microbial Biology
and of Molecular and Cell Biology, University of California,
Berkeley, Berkeley, California 94720-3102,1
and
U.S. Geological Survey, Lansing, Michigan
489112
Received 26 May 1998/Accepted 28 July 1998
A culture-independent molecular phylogenetic approach was used to
survey constituents of microbial communities associated with an aquifer
contaminated with hydrocarbons (mainly jet fuel) and chlorinated
solvents undergoing intrinsic bioremediation. Samples were obtained
from three redox zones: methanogenic, methanogenic-sulfate reducing,
and iron or sulfate reducing. Small-subunit rRNA genes were
amplified directly from aquifer material DNA by PCR with universally conserved or Bacteria- or
Archaea-specific primers and were cloned. A total of 812 clones were screened by restriction fragment length polymorphisms
(RFLP), approximately 50% of which were unique. All RFLP
types that occurred more than once in the libraries, as well as many of
the unique types, were sequenced. A total of 104 (94 bacterial and 10 archaeal) sequence types were determined. Of the 94 bacterial sequence
types, 10 have no phylogenetic association with known taxonomic
divisions and are phylogenetically grouped in six novel division level
groups (candidate divisions WS1 to WS6); 21 belong to four recently
described candidate divisions with no cultivated representatives (OP5,
OP8, OP10, and OP11); and 63 are phylogenetically associated with 10 well-recognized divisions. The physiology of two particularly abundant
sequence types obtained from the methanogenic zone could be inferred
from their phylogenetic association with groups of microorganisms with a consistent phenotype. One of these sequence types is associated with
the genus Syntrophus; Syntrophus spp. produce
energy from the anaerobic oxidation of organic acids, with the
production of acetate and hydrogen. The organism represented by the
other sequence type is closely related to Methanosaeta
spp., which are known to be capable of energy generation only through
aceticlastic methanogenesis. We hypothesize, therefore, that the
terminal step of hydrocarbon degradation in the methanogenic zone of
the aquifer is aceticlastic methanogenesis and that the microorganisms
represented by these two sequence types occur in syntrophic
association.
0099-2240/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Microbial Diversity in a Hydrocarbon- and
Chlorinated-Solvent-Contaminated Aquifer Undergoing Intrinsic
Bioremediation
*
Corresponding author. Mailing address: Departments of
Plant and Microbial Biology and of Molecular and Cell Biology,
University of California, Berkeley, CA 94720-3102. Phone: (510)
643-2571. Fax: (510) 642-4995. E-mail:
nrpace{at}nature.berkeley.edu.
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