Dominant microbial populations in limestone-corroding stream biofilms, Frasassi cave system, Italy

Jennifer L. Macalady, Ezra H. Lyon, Bess Koffman, Lindsey K. Albertson, Katja Meyer, Sandro Galdenzi, Sandro Mariani

Research output: Contribution to journalArticlepeer-review

139 Scopus citations

Abstract

Waters from an extensive sulfide-rich aquifer emerge in the Frasassi cave system, where they mix with oxygen-rich percolating water and cave air over a large surface area. The actively forming cave complex hosts a microbial community, including conspicuous white biofilms coating surfaces in cave streams, that is isolated from surface sources of C and N. Two distinct biofilm morphologies were observed in the streams over a 4-year period. Bacterial 16S rDNA libraries were constructed from samples of each biofilm type collected from Grotta Sulfurea in 2002. β-, γ-, δ-, and ε-proteobacteria in sulfur-cycling clades accounted for ≥75% of clones in both biofilms. Sulfate-reducing and sulfur-disproportionating δ-proteobacterial sequences in the clone libraries were abundant and diverse (34% of phylotypes). Biofilm samples of both types were later collected at the same location and at an additional sample site in Ramo Sulfureo and examined, using fluorescence in situ hybridization (FISH). The biomass of all six stream biofilms was dominated by filamentous γ-proteobacteria with Beggiatoa-like and/or Thiothrix-like cells containing abundant sulfur inclusions. The biomass of ε- proteobacteria detected using FISH was consistently small, ranging from 0 to less than 15% of the total biomass. Our results suggest that S cycling within the stream biofilms is an important feature of the cave biogeochemistry. Such cycling represents positive biological feedback to sulfuric acid speleogenesis and related processes that create subsurface porosity in carbonate rocks.

Original languageEnglish (US)
Pages (from-to)5596-5609
Number of pages14
JournalApplied and environmental microbiology
Volume72
Issue number8
DOIs
StatePublished - Aug 2006

All Science Journal Classification (ASJC) codes

  • Biotechnology
  • Food Science
  • Applied Microbiology and Biotechnology
  • Ecology

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