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AMD Acidophile Heterotroph Network

Ecological State STABLE
Environment acid mine drainage
ENVO:00002186
Source File AMD_Acidophile_Heterotroph_Network.yaml

A heterotrophic microbial network in acid mine drainage (AMD) systems dominated by Acidiphilium species and related acidophilic heterotrophs. This community plays a crucial role in coupling carbon and iron cycles in extremely acidic environments, supporting autotrophic iron oxidizers through organic matter processing and nutrient remineralization. The network thrives at pH 2-4 in AMD sites globally, where heterotrophs metabolize organic compounds produced by autotrophs or released from lysed cells, preventing organic carbon accumulation that would inhibit autotrophic iron oxidizers. Key members include Acidiphilium multivorum (facultative Fe(III) reducer and organic carbon degrader), Ferrimicrobium acidiphilum (iron-oxidizing heterotroph and dissolved organic carbon remover), Acidocella facilis (obligate aerobic heterotroph), Acidisphaera rubrifaciens (photoheterotrophic bacteriochlorophyll producer), and Acidobacterium capsulatum (chemoorganotrophic acidophile). These organisms collectively perform organic matter degradation, ferric iron reduction, biofilm formation, and nutrient cycling. The heterotroph-autotroph coupling maintains community stability by removing inhibitory organic carbon, recycling nutrients (nitrogen, phosphorus), generating ferrous iron for autotrophic energy generation, and facilitating metal tolerance through extracellular polymeric substances (EPS) production. This network represents a critical functional guild in AMD ecosystems, enabling the persistence of autotrophic iron-oxidizing communities through metabolic cooperation and resource partitioning.

Taxonomy

Taxon Ontology ID Functional Roles Abundance
Acidiphilium multivorum NCBITaxon:62140
CROSS_FEEDER SYNTROPHIC_PARTNER
DOMINANT
Ferrimicrobium acidiphilum NCBITaxon:121039
CROSS_FEEDER PRIMARY_PRODUCER
COMMON
Acidiphilium cryptum NCBITaxon:524
CROSS_FEEDER SYNTROPHIC_PARTNER
COMMON
Acidocella facilis NCBITaxon:525
CROSS_FEEDER
COMMON
Acidisphaera rubrifaciens NCBITaxon:50715
CROSS_FEEDER
RARE
Acidobacterium capsulatum NCBITaxon:33075
CROSS_FEEDER
RARE

Ecological Interactions

Organic Carbon Scavenging and Remineralization

CROSS_FEEDING

Source Taxon: Acidiphilium multivorum

Metabolites: organic molecular entity (CHEBI:50860), carbon dioxide (CHEBI:16526), ammonium (CHEBI:28938), phosphate (CHEBI:18367)

Biological Processes:

Evidence

  • doi:10.3389/fmicb.2015.00475 - SUPPORT (IN_VIVO)
    "Low-pH conditions appear to be the main factor underlying the limited diversity of the microbial populations thriving in these environments, although temperature, ionic composition, total organic carbon, and dissolved oxygen are also considered to significantly influence their microbial life"
  • doi:10.1128/msystems.00867-20 - SUPPORT (REVIEW)
    "We found in the genomes of Acidiphilium an abundant repertoire of horizontally transferred genes (HTGs) contributing to environmental adaption and metabolic ability expansion, as indicated by phylogenetic reconstruction and gene context comparison"

Ferric Iron Reduction and Ferrous Iron Regeneration

MUTUALISM

Source Taxon: Acidiphilium multivorum

Metabolites: iron(3+) (CHEBI:29034), iron(2+) (CHEBI:29033), glucose (CHEBI:17234), organic acid (CHEBI:64709)

Biological Processes:

Downstream Effects:
→ Organic Carbon Scavenging and Remineralization

Evidence

  • PMID:10427060 - SUPPORT (IN_VITRO)
    "These collective results indicate that the in situ reduction of Fe(III) in acidic sediments can be mediated by heterotrophic Acidiphilium species that are capable of coupling the reduction of Fe(III) to the complete oxidation of a large variety of substrates including glucose and H(2)."
  • doi:10.1093/femsec/49.1.137 - SUPPORT (IN_VITRO)
    "Iron respiration by Acidiphilium cryptum at pH 5"

Heterotrophic Iron Oxidation by Ferrimicrobium

CROSS_FEEDING

Source Taxon: Ferrimicrobium acidiphilum

Metabolites: iron(2+) (CHEBI:29033), iron(3+) (CHEBI:29034), organic molecular entity (CHEBI:50860)

Biological Processes:

Evidence

  • doi:10.1099/ijs.0.65409-0 - SUPPORT (IN_VITRO)
    "Two novel extremely acidophilic, iron-oxidizing actinobacteria were isolated, one from a mine site in North Wales, UK (isolate T23(T)), and the other from a geothermal site in Yellowstone National Park, Wyoming, USA (Y005(T))"
  • doi:10.1128/aem.01906-20 - SUPPORT (IN_VITRO)
    "acidiphilum as it respired on extracellular iron using an integrating cavity absorption meter that permitted accurate optical measurements in turbid suspensions of the intact bacterium under physiological conditions"

Biofilm Formation and Metal Sequestration

MUTUALISM

Metabolites: polysaccharide (CHEBI:18154), protein (CHEBI:36080), copper(2+) (CHEBI:29036), zinc(2+) (CHEBI:29105)

Biological Processes:

Evidence

  • doi:10.1128/aem.02301-09 - SUPPORT (IN_VIVO)
    "Characterization of Extracellular Polymeric Substances from Acidophilic Microbial Biofilms"
  • PMID:18330567 - SUPPORT (IN_VITRO)
    "The efficiency of five extraction methods for extracellular polymeric substances (EPS) was compared on three benthic eukaryotic biofilms isolated from an extreme acidic river, Río Tinto (SW, Spain)"

Environmental Factors

Factor Value Unit
pH Range 2.0-4.0 pH
Dissolved Organic Carbon Variable, 10-500 mg/L mg/L DOC
Oxygen Availability Aerobic to anaerobic qualitative
Temperature 15-40 °C
Metal Concentrations Fe: 0.5-5 g/L; Zn: 100-1000 mg/L; Cu: 50-500 mg/L g/L or mg/L