Ferroplasma-Leptospirillum Iron-Cycling Syntrophy

HYPOTHESIZED: L. ferriphilum growth supplies organic matter usable by F. acidiphilum. The inspected Merino abstract states this as the study hypothesis, not a quantified release flux or a resolved substrate identity. Retain the upstream supply context without asserting Calvin-Benson-Bassham fixation, mineral-specific dissolution, toxic accumulation thresholds or their relief in the exact pair.

Source Taxon: Leptospirillum ferriphilum

Metabolites: organic molecular entity (CHEBI:50860 · MediaIngredientMech · CMMMech)

Evidence

• PMID:27535541 - PARTIAL (IN_VITRO)
  "The hypothesis of this work is that F. acidiphilum uses the organic matter secreted by L. ferriphilum for growth"

HYPOTHESIZED: Organic matter supplied by L. ferriphilum contributes carbon to F. acidiphilum BRL-115 and its removal relieves inhibition of the bacterium. Reciprocal filtered-supernatant growth supports soluble partner effects, but the inspected abstract does not establish identified transferred substrates, assimilation flux or detoxification thresholds. BRL-115 chemomixotrophy and the 0.04% yeast-extract growth optimum are characterization results, not proof of the proposed mediator in mixed culture. CROSS_FEEDING denotes this proposed transfer, not established obligate syntrophy.

Source Taxon: Leptospirillum ferriphilum

Target Taxon: Ferroplasma acidiphilum

Metabolites: organic molecular entity (CHEBI:50860 · MediaIngredientMech · CMMMech)

Evidence

• PMID:27535541 - PARTIAL (IN_VITRO)
  "The hypothesis of this work is that F. acidiphilum uses the organic matter secreted by L. ferriphilum for growth"
• PMID:27535541 - SUPPORT (IN_VITRO)
  "acidiphilum, strain BRL-115 is a chemomixotrophic organism, and its growth is maximized with yeast extract at a concentration of 0.04% wt/vol"

Ferroplasma iron metabolism is physiological context, not an observed niche-partitioning interaction. Ferrer studied strain Y(T), reporting ferrous-iron oxidation and iron-rich proteins; this is not BRL-115 in the Leptospirillum pair. Wilson compared isolated rusticyanins: the archaeal FaR had similar redox potential but slower electron transfer than AfR. These sources do not establish lower-oxygen complementarity, a pair-specific membrane complex, competition relief or stable coexistence. Protein electron-transfer properties do not measure consortium iron-oxidation flux.

Source Taxon: Ferroplasma acidiphilum

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

Evidence

• PMID:38593609 - SUPPORT (IN_VITRO)
  "While both N0 and FaR show redox potentials similar to that of AfR their electron transport rates were significantly slower."
• PMID:17203061 - SUPPORT (IN_VITRO)
  "F. acidiphilum strain Y(T) is a chemoautotroph"

In reciprocal assays, each organism grew favorably in filtered medium from its partner. This supports diffusible partner-associated growth effects without requiring direct cell contact in those assays, but does not identify the mediators, show equal reciprocal benefit in simultaneous coculture or prove obligatory syntrophy. Mixed-culture growth rates were used as input to flux-balance analysis; model behavior is not independent measurement of exchanged flux. Organic-matter consumption cannot be treated as the demonstrated cause of both reciprocal responses.

Participating Taxa: Leptospirillum ferriphilum, Ferroplasma acidiphilum

Biological Processes:

• response to other organism (GO:0051707 · PathwayMech)

Evidence

• PMID:27535541 - SUPPORT (IN_VITRO)
  "acidiphilum supernatant and vice versa, it was observed that in both cases cell growth is favorably affected by the presence of the filtered medium of the other microorganism, proving a synergistic interaction between these species"