Affiliation:
1. Universidad Autónoma de Madrid, Departamento de Biología Molecular, 28049 Madrid, Spain
2. Centro de Biología Molecular Severo Ochoa, UAM-CSIC, 28049 Madrid, Spain
3. Centro de Astrobiología, INTA-CSIC, Ctra. Ajalvir-Torrejón de Ardoz, 28850 Madrid, Spain
Abstract
ABSTRACT
The Tinto River is an extreme environment located at the core of the Iberian Pyritic Belt (IPB). It is an unusual ecosystem due to its size (100 km long), constant acidic pH (mean pH, 2.3), and high concentration of heavy metals, iron, and sulfate in its waters, characteristics that make the Tinto River Basin comparable to acidic mine drainage (AMD) systems. In this paper we present an extensive survey of the Tinto River sediment microbiota using two culture-independent approaches: denaturing gradient gel electrophoresis and cloning of 16S rRNA genes. The taxonomic affiliation of the
Bacteria
showed a high degree of biodiversity, falling into 5 different phyla:
Proteobacteria
,
Firmicutes
,
Bacteroidetes
,
Acidobacteria
, and
Actinobacteria
; meanwhile, all the
Archaea
were affiliated with the order
Thermoplasmatales
. Microorganisms involved in the iron (
Acidithiobacillus ferrooxidans
,
Sulfobacillus
spp.,
Ferroplasma
spp., etc.), sulfur (
Desulfurella
spp.,
Desulfosporosinus
spp.,
Thermodesulfobium
spp., etc.), and carbon (
Acidiphilium
spp.,
Bacillus
spp.,
Clostridium
spp.,
Acidobacterium
spp., etc.) cycles were identified, and their distribution was correlated with physicochemical parameters of the sediments. Ferric iron was the main electron acceptor for the oxidation of organic matter in the most acid and oxidizing layers, so acidophilic facultative Fe(III)-reducing bacteria appeared widely in the clone libraries. With increasing pH, the solubility of iron decreases and sulfate-reducing bacteria become dominant, with the ecological role of methanogens being insignificant. Considering the identified microorganisms—which, according to the rarefaction curves and Good's coverage values, cover almost all of the diversity—and their corresponding metabolism, we suggest a model of the iron, sulfur, and organic matter cycles in AMD-related sediments.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology