TraitMech

TraitMech › ECOLOGY

free-living

traitmech:000048 · CLASS · REVIEWED

A habitat association in which an organism lives independently in the environment, not obligately associated with a host.

Free-living lifestyle is independent of host association

Evidence-backed causal sketch linking environmental habitat occupancy to a host-independent free-living lifestyle.

Free-living lifestyle is independent of host association Interactive directed graph showing evidence-backed causal relationships for free-living.

Edge evidence

  • environmental habitat enables free-living RO:0002327

    Persistent occupancy of environmental habitats realizes the free-living lifestyle.

    • DOI:10.1038/nrmicro1341 Martiny et al. document biogeographic patterning of free-living microbial taxa.
  • free-living associated with biogeographic community structure biolink:associated_with

    Free-living taxa show environment-structured global distributions.

    • DOI:10.1038/nrmicro.2017.171 Poole et al. describe the free-living soil phase of rhizobia distinct from their host-associated phase.
  • complete metabolic capacity for carbon/nitrogen/sulfur/cofactors required for free-living

    Self-sufficient metabolic pathways for carbon, nitrogen, sulfur and cofactors are required for a host-independent free-living life strategy.

    • DOI:10.1186/s12915-024-02013-w Reversion to free-living is rare because parasites often lose metabolic pathways essential to a free-living life strategy.
    • DOI:10.1128/aem.01900-23 Symbiotic Fluviibacter showed reduced metabolic capacities and host dependence for carbon, organic nitrogen, sulfur, and cofactors.
  • ectoine biosynthetic pathway enables osmotic stress tolerance RO:0002327

    Ectoine synthesis provides compatible solutes that confer osmotic stress tolerance during environmental persistence.

    • DOI:10.48550/arxiv.2302.00582 Crossing salinity barriers requires osmotic-stress mechanisms; marine adaptation includes components involved in ectoine synthesis.
    • DOI:10.1371/journal.pone.0287947 Paracoccus carried the ectoine cluster in all strains.
  • glycine betaine transport/biosynthesis enables osmotic stress tolerance RO:0002327

    Glycine betaine transport/biosynthesis confers osmoprotection under environmental stress.

    • DOI:10.1371/journal.pone.0287947 betA-betB, betI operon and multiple glycine-betaine transporters link these systems to persistence under environmental stress.
  • trehalose biosynthesis/transport enables stress tolerance in fluctuating environments RO:0002327

    Trehalose synthesis/transport provides compatible-solute protection under fluctuating environmental conditions.

    • DOI:10.1371/journal.pone.0287947 Trehalose synthesis/transport widely encoded; compatible-solute systems discussed as persistence traits, lost in some host-associated lineages.
  • osmotic stress tolerance promotes free-living RO:0002213

    Osmoadaptation supports persistence in unstable/saline environments characteristic of the free-living lifestyle.

    • DOI:10.48550/arxiv.2302.00582 Ectoine-related osmoadaptation is highlighted as part of adaptation to unstable or saline environmental conditions in free-living lineages.

Knowledge gaps & discussions (1)

KNOWLEDGE_GAP OPEN Knowledge gap for free-living: Interactions between parasites and the gut microbiota play a key role in immune responses and susceptibility to zoonotic diseases; however, many aspects of how protozoan infections alter microbial diversity and how these changes influence parasite pathogenicity and host defense remain poorly understood.

Surfaced by the Europe PMC literature gap-signal scan (categories: explicit_gap, future_work, limitations_barriers, unclear_unknown). Curator review required: set attaches_to, refine the prompt, and weigh the cited evidence.

4 evidence item(s)
NO_EVIDENCE PMID:41989588 Interactions between parasites and the gut microbiota play a key role in immune responses and susceptibility to zoonotic diseases; however, many aspects of how protozoan infections alter microbial diversity and how these changes influence parasite pathogenicity and host defense remain poorly understood. Gap-signal sentence (unclear_unknown) from the cited abstract.
NO_EVIDENCE PMID:42039802 Engineered microbial assemblies tailored to specific host plants and environmental conditions have shown potential in stabilizing crop performance during drought, salinity, and nutrient limitations. Gap-signal sentence (limitations_barriers) from the cited abstract.
NO_EVIDENCE PMID:41943163 OBJECTIVES: Oxo-polyethylene (oxo-PE) is marketed as a biodegradable plastic, yet its environmental degradation remains poorly understood, particularly in marine contexts. Gap-signal sentence (unclear_unknown) from the cited abstract.
NO_EVIDENCE PMID:42125129 However, contradictions persist regarding pH's effect on microbial diversity, with unresolved questions about how specific environmental conditions regulate microbial taxa. Gap-signal sentence (explicit_gap) from the cited abstract.

Provenance

Source
METPO (2025-11-25)
Definition source
DOI:10.1038/nrmicro1341

Parent traits (1)

kg-microbe context

Matched 1 kg-microbe node via parent_proxy.

  • METPO:1000059 [-2.682, -2.070, -3.656, -0.652, …]

512-dim DeepWalkSkipGramEnsmallen embedding from kg-microbe (2026-04-25).

Nearest neighbors in embedding space

Top-8 cosine-similar METPO traits from the 2026-04-25 deepwalk (512-D).

Curation history

  1. · PROPOSED_FROM_RESEARCH · claude

    Proposed candidate ECOLOGY trait (free-living); sub-variant of habitat association.

  2. · CURATED_CAUSAL_GRAPH · claude

    Added evidence-backed causal graph (free-living / environmental habitat) with RO/biolink predicate groundings; promoted PROPOSED to REVIEWED.

  3. · ENRICH_CAUSAL_GRAPH · claude

    Added 5 evidence-backed generic edges (6 new nodes) from the deep-research report.

  4. · GROUND_CAUSAL_PREDICATES · claude

    Grounded 4 causal-edge predicate_id field(s) via mappings/predicate_grounding.tsv (RO:0002327×3, RO:0002213×1).