Iberian Pit Lake Stratified Community

PARTIAL - Cueva de la Mora omics associate chemocline populations with iron oxidation and deep Proteobacteria with iron reduction. The 2013 NSC/Concepcion study instead combines geochemistry with clone-library identities to propose site-specific iron cycling. These positive observations support redox-functional potential, not direct flux by every listed taxon or demonstrated competitive niche partitioning. The canonical participants summarize roles across studies and are not an assayed four-member unit.

Participating Taxa: Leptospirillum, Acidithiobacillus ferrooxidans, Candidatus Acidulodesulfobacterium, Acidiphilium

Metabolites: Fe(II) (CHEBI:29033 · MediaIngredientMech · CMMMech), Fe(III) (CHEBI:29034 · MediaIngredientMech · CMMMech)

Evidence

• PMID:36123522 - PARTIAL (IN_VIVO)
  "The chemocline had activity for iron(II) oxidation carried out by populations of Ca. Acidulodesulfobacterium, Ferrovum, Leptospirillium, and Armatimonadetes"
• PMID:36123522 - PARTIAL (IN_VIVO)
  "iron(III) reduction was only detected in the deep layer affiliated with Proteobacteria"
• PMID:23840525 - PARTIAL (IN_VIVO)
  "facultative iron reducing bacteria and archaea (Acidithiobacillus ferrooxidans, Acidiphilium, Actinobacteria, Acidimicrobiales, Ferroplasma) detected in the bottom layer"

PARTIAL - the Cueva de la Mora abstract reports active chemocline sulfate-reducing populations and deep-layer precipitation potential, constrained by carbon quality/quantity and possible groundwater oxygen input. In separate FC/La Zarza lakes, metal profiles, putative sulfidogenic taxa and observed FC copper/zinc sulfide particles support a biosulfidogenesis model. The observed particles are precipitated sulfides, not dissolved sulfides. This is not demonstrated pairwise syntrophy or proof that both canonical taxa mediate every lake result; sulfur reduction/disproportionation and sulfate reduction have distinct proposed roles.

Participating Taxa: Desulfomonile, Candidatus Acidulodesulfobacterium

Metabolites: sulfate (CHEBI:16189 · MediaIngredientMech · CMMMech), hydrogen sulfide (CHEBI:16136 · MediaIngredientMech · CMMMech), copper sulfide (CHEBI:51110 · MediaIngredientMech · CMMMech)

Biological Processes:

• dissimilatory sulfate reduction (GO:0019420 · PathwayMech)

Evidence

• PMID:36123522 - PARTIAL (IN_VIVO)
  "Abundant sulfate-reducing Desulfomonile and Ca. Acidulodesulfobacterium populations were active in the chemocline"
• PMID:36123522 - PARTIAL (IN_VIVO)
  "sulfide mineral precipitation in the deep layer"
• doi:10.3390/microorganisms8091275 - PARTIAL (IN_VIVO)
  "The detection of Cu and Zn sulfides in the monimolimnion of FC suggests precipitation of dissolved metals as metal sulfides"

Cueva de la Mora omics identify active Coccomyxa onubensis as dominant in the upper layer and chemocline. PARTIAL - its proposed primary-production contribution does not quantify carbon fixation or selectively demonstrate algal export to a named sulfate reducer. FC/La Zarza showed very limited phototrophic indicators and are not evidence for the same algal route. The 2020 authors did not infer that organic carbon was necessarily the limiting factor in those two lakes.

Participating Taxa: Coccomyxa onubensis

Metabolites: organic molecular entity (CHEBI:50860 · MediaIngredientMech · CMMMech), carbon dioxide (CHEBI:16526 · MediaIngredientMech · CMMMech)

Biological Processes:

• photosynthesis (GO:0015979 · PathwayMech)
• carbon fixation (GO:0015977 · PathwayMech)

Evidence

• PMID:36123522 - SUPPORT (IN_VIVO)
  "We found that active green alga Coccomyxa onubensis dominated the upper layer and chemocline"
• PMID:36123522 - PARTIAL (IN_VIVO)
  "active green alga Coccomyxa onubensis dominated the upper layer and chemocline"

PARTIAL - uncultured Thermoplasmatales dominated the deep Cueva de la Mora layer and were predicted to have heterotrophic and sulfide-oxidizing activity. The positive omics inference does not establish a uniform metabolism for the whole order, measured organic-carbon scavenging that benefits another taxon, or a donor route to methanogens. Groundwater oxygen and carbon constraints on sulfide precipitation are community-level proposals, not proof of this archaeal mediation.

Participating Taxa: Thermoplasmatales

Biological Processes:

• sulfide oxidation (GO:0019418 · PathwayMech)

Evidence

• PMID:36123522 - PARTIAL (IN_VIVO)
  "Heterotrophic archaeal populations with predicted activity for sulfide oxidation related to uncultured Thermoplasmatales dominated in the deep layer"
• PMID:36123522 - PARTIAL (IN_VIVO)
  "quantity and quality of organic carbon reaching the deep layer"

Low relative-abundance reads classified as methanogens, including Methanobrevibacter, were detected in FC and La Zarza. This supports presence of methanogen-associated sequences and possible methanogenic potential, not measured methane production at the sampled depth. A separate deep-borehole biomarker study does not establish a lake partner-to-Methanobrevibacter pathway. No exact methane concentration or hydrogen donor is assigned to these observations.

Participating Taxa: Methanobrevibacter

Metabolites: methane (CHEBI:16183 · MediaIngredientMech · CMMMech), hydrogen (CHEBI:18276 · MediaIngredientMech · CMMMech)

Biological Processes:

• methanogenesis (GO:0015948 · PathwayMech)

Evidence

• doi:10.3390/microorganisms8091275 - SUPPORT (IN_VIVO)
  "Furthermore, the detection of reads classified as methanogens and Desulfosporosinus spp., although at low relative abundance, represents one of the lowest pH values (2.9 in LZ) at which these taxa have been reported, to our knowledge"