predatory bacterium

Deep research

Generated by just research-trait; source: research/traits/ecology/predatory_bacterium-deep-research-falcon.md

# Curation-focused research report: predatory bacterium

## 1. Scope summary

**Trait:** `traitmech:000054`  
**Category:** ECOLOGY; **term kind:** CLASS; **mapping:** REVIEWED  
**Parent supplied by the template:** `METPO:1000059`  
**Recommended operational definition:** a trophic lifestyle in which a bacterium actively attacks and kills living microbial prey and acquires prey-derived biomass or nutrients. The defining outcome is therefore not merely antagonism, but the causal sequence **active attack → prey death/lysis → nutrient acquisition**.

The class should encompass several independently evolved mechanisms:

1. **Endoperiplasmic predation:** *Bdellovibrio bacteriovorus* enters the periplasm of Gram-negative prey, converts it into a bdelloplast, consumes prey contents, grows filamentously, divides non-binarily, and lyses the remnant to exit. A sheathed polar flagellum promotes collision, type IV pili mediate attachment, and localized cell-wall remodeling permits entry. (kaplan2023bdellovibriopredationcycle pages 1-3, kaplan2023bdellovibriopredationcycle pages 3-4)
2. **Obligate epibiotic predation:** predators such as *Bdellovibrio exovorus* or *Micavibrio* remain outside the prey while feeding through an envelope junction. This is predation even without invasion because prey is killed and its biomass is consumed.
3. **Wolf-pack or extracellular/contact predation:** *Myxococcus xanthus* and related facultative predators use coordinated motility, contact-dependent systems, hydrolytic enzymes, secondary metabolites, and outer-membrane vesicles to kill prey externally. Wolf-pack predators can grow axenically, so obligate prey dependence is not part of the parent trait definition. (alexakis2024predatorybacteriain pages 1-2, mun2023predatorybacteriaas pages 1-2)
4. **Ixotrophy:** filamentous *Aureispira* captures motile prey using T9SS-secreted grappling hooks, punctures prey through a T6SS, and assimilates prey-derived material. This establishes a particularly complete molecular chain from capture through killing to nutrient uptake. (lien2024mechanismofbacterial pages 1-5, lien2024mechanismofbacterial pages 10-13, lien2024mechanismofbacterial pages 13-16)
5. **Facultative contact predation:** bradymonabacteria kill only after direct contact in the tested system but can proliferate without prey. This is a boundary case that belongs under the trait if prey-derived nutrient use is demonstrated or adequately supported. (wang2024thepredatoryproperties pages 5-8, wang2024thepredatoryproperties pages 1-2)

### Boundary rules

**Include:** active killing followed by consumption, whether prey is entered, fed upon externally, or lysed at short range. Both obligate and facultative predators qualify.

**Do not infer the trait from:**

- secretion of antibiotics or bacteriocins alone;
- competition, kin discrimination, or T6SS-mediated antagonism without evidence of trophic benefit;
- scavenging dead biomass without active killing;
- parasitic attachment that harms but does not kill/consume prey;
- bacteriophage susceptibility or phage-mediated killing;
- hydrolytic-enzyme abundance, genome annotation, plaque formation, or prey decline alone.

A practical assay should demonstrate at least prey killing plus one of: predator growth dependent on prey, incorporation of isotope-labelled prey material, loss of predation after disruption of an attack apparatus, or direct imaging of prey consumption.

## 2. Current mechanistic understanding

For the best-resolved endoperiplasmic model, the lifecycle can be represented as:

**motile attack phase → prey collision → T4P/MAT-mediated recognition and attachment → local prey-envelope remodeling → portal-mediated entry and sealing → prey killing and macromolecule hydrolysis → nutrient-dependent filamentous growth/chromosome replication → non-binary septation → prey-remnant lysis and progeny exit.**

Cryo-electron tomography directly visualized T4aP connecting predator and prey and an electron-dense attachment plaque spanning the contact region. The plaque measured approximately 15–70 nm across. During invasion it was replaced by a portal that bridged the predator and prey outer membranes; the predator’s envelope spacing was reduced by approximately 50% at the entry point, supporting a tight-seal model. (kaplan2023bdellovibriopredationcycle pages 4-6, kaplan2023bdellovibriopredationcycle pages 3-4, kaplan2023bdellovibriopredationcycle media 45a9f5f1, kaplan2023bdellovibriopredationcycle media 2e25126f)

The same work overturned the prior assumption that the flagellum is simply shed: after committed attachment, it is resorbed into the predator periplasm and degraded. This is biologically important but should be modeled as lifecycle remodeling, not as a direct cause of prey killing. (kaplan2023bdellovibriopredationcycle pages 1-3, kaplan2023bdellovibriopredationcycle pages 4-6)

## 3. Candidate nodes grouped by type

### A. Taxa and predation modes

- *Bdellovibrio bacteriovorus* — endoperiplasmic predator; label plus NCBI Taxonomy mapping should be resolved during implementation.
- *Bdellovibrio exovorus* — obligate epibiotic predator.
- *Myxococcus xanthus* — facultative wolf-pack/contact predator.
- *Aureispira* sp. CCB-QB1 — ixotrophic filamentous predator.
- Bradymonabacteria/Bradymonadia — facultative prey-dependent, contact predator.
- Gram-negative bacterial prey; *Escherichia coli*, *Vibrio cholerae*, *Vibrio campbellii*, *Proteus mirabilis*.

Because taxonomic accessions were not independently verified here, retain labels until checked against the current NCBI Taxonomy release rather than inserting remembered identifiers.

### B. Cellular structures and localizations

- sheathed unipolar flagellum — candidate grounding: `GO:0009288` only after checking that the ontology label and intended granularity match;
- type IV pilus/type IVa pilus/type IVb pilus;
- predator invasive or “biting” pole;

Showing the first 60 of 338 lines of findings; the linked file also carries the run's front matter and the prompt it was given — read the full report.