HR: 0830h
AN: B51C-0969    [PDF]
TI: Microbiology and Geochemistry of Acidic Cave Biofilms in the Frasassi Caves, Italy
AU: * Meyer, K M
EM: kmeyer@geosc.psu.edu
AF: Carleton College, 1 North College Street, Northfield, MN 55057 United States
AU: Cleaveland, L C
EM: Laura_Cleaveland@brown.edu
AF: Carleton College, 1 North College Street, Northfield, MN 55057 United States
AU: Galdenzi, S
EM: sagalde@tin.it
AF: Italian Speleological Institute, Frasassi Headquarters, Genga, 60040 Italy
AU: Macalady, J L
EM: jmacalad@carleton.edu
AF: Carleton College, 1 North College Street, Northfield, MN 55057 United States
AB: Acidic (pH 2-4) and extremely acidic (pH 0-1) biofilms in sulfidic regions of the Frasassi cave system are relatively simple, chemoautotrophic microbial communities. As such, they serve as model systems to test relationships between microbial diversity and physical and geochemical factors. Both biofilm types are isolated from surface sources of C and N and are ultimately powered by oxidation of H$_{2}$S present in the cave atmosphere. pH 2-4 biofilms consist of cells in close association with sub-um to sub-mm mineral grains (primarily CaSO$_{4}$) coating cave walls. Direct counts of cells stained with 4',6-diamidino-2-phenylindole, hydrochloride (DAPI) yield a biomass estimate of 7.5 x 10$^{6}$ to 1.3 x 10$^{7}$ cells per cm$^{3}$. The great majority of these cells are either dormant (contain few ribosomes) or cells which do not hybridize with either bacteria- or archaea-specific oligonucleotide probes. Sparse clusters of short rod and coccus-shaped cells hybridized with a bacteria-specific Fluorescent In Situ Hybridization (FISH) probe. Polymerase Chain Reaction (PCR) amplification of 16S rDNA was successful with bacteria-specific primers as well as with several sets of archaeal-specific primers, suggesting that some of the "dormant" cells are archaea. Extremely acidic biofilms (snottites) drip from macroscopic (1-2 cm length), reddish CaSO$_{4}$ crystals on the cave walls. DAPI-staining and FISH revealed abundant bacterial rods, bacterial filaments, and fungi in the snottites. Future work will characterize the acidic cave wall biofilms, as well as neutral-pH cave stream biofilms, using 16S rDNA clone libraries in order to determine whether pH is an important factor controlling microbial diversity.
DE: 0400 Biogeosciences
SC: Biogeosciences [B]
MN: 2003 Fall Meeting