SwrD (formerly YlzI) is a small (~71 aa) swarming-specific enhancer of flagellar motor power in Bacillus subtilis. Located in the fla-che operon adjacent to fliL, SwrD increases power delivery (torque) per flagellum by acting at the level of MotAB stator activity, without affecting stator abundance or flagellar number. Deletion of swrD abolishes swarming motility and reduces swimming speed (~2-fold) and single-flagellum torque (~6-fold). These phenotypes are rescued by MotAB overexpression, demonstrating that SwrD functions to enhance motor power output. SwrD homologs often co-occur with motAB across diverse bacteria, suggesting a conserved role in stator-dependent torque enhancement for surface motility.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0071978 bacterial-type flagellum-dependent swarming motility | IBA GO_REF:0000033 | ACCEPT | Summary: This phylogenetic annotation (IBA) is well-supported by experimental evidence from PMID:29061663. SwrD is specifically required for swarming motility; deletion abolishes swarming on solid surfaces while cells retain swimming ability (albeit reduced). Reason: The IBA annotation aligns with direct experimental evidence. Hall et al. (2018) demonstrated that swrD mutants completely fail to swarm on 0.7% agar, while complementation restores swarming. The phylogenetic inference is consistent with the protein's conserved function across Firmicutes and other bacterial lineages where SwrD homologs co-occur with motAB. Supporting Evidence: PMID:29061663 Here we report a new gene, swrD, located within the 32 gene fla-che operon dedicated to flagellar biosynthesis and chemotaxis, which when mutated abolished swarming motility. PMID:29061663 SwrD was not required for surfactant production, flagellar gene expression, or an increase in flagellar number. Instead, SwrD was required to increase flagellar power. file:BACSU/swrD/swrD-deep-research-falcon.md See deep research file for comprehensive analysis |
| GO:0071978 bacterial-type flagellum-dependent swarming motility | IMP PMID:29061663 SwrD (YlzI) Promotes Swarming in Bacillus subtilis by Increa... | ACCEPT | Summary: This is the primary experimental paper characterizing SwrD function. Hall et al. (2018) demonstrated through deletion and complementation experiments that SwrD is essential for swarming motility by increasing power to flagellar motors via MotAB stator activity. Reason: PMID:29061663 provides definitive experimental evidence for SwrD's role in swarming. The study shows: (1) swrD deletion abolishes swarming on 0.7% agar, (2) complementation restores swarming, (3) the phenotype is not due to reduced flagellar number or surfactant production, and (4) MotAB overexpression rescues swrD-related phenotypes. This directly demonstrates that SwrD is involved in bacterial-type flagellum-dependent swarming motility. Supporting Evidence: PMID:29061663 Here we report a new gene, swrD, located within the 32 gene fla-che operon dedicated to flagellar biosynthesis and chemotaxis, which when mutated abolished swarming motility. PMID:29061663 We conclude that swarming motility requires flagellar power in excess of that which is needed to swim. PMID:29061663 SwrD likely increases power in other organisms, like the Firmicutes, Clostridia, Spirochaetes, and the Deltaproteobacteria. |
| GO:0071978 bacterial-type flagellum-dependent swarming motility | IMP PMID:25313396 FlgM is secreted by the flagellar export apparatus in Bacill... | REMOVE | Summary: This annotation is INCORRECT. PMID:25313396 (Calvo and Kearns, 2015) is about FlgM secretion by the flagellar export apparatus in Bacillus subtilis. The paper does NOT mention swrD or ylzI anywhere. This appears to be an erroneous annotation. Reason: PMID:25313396 is titled "FlgM is secreted by the flagellar export apparatus in Bacillus subtilis" and focuses entirely on the anti-sigma factor FlgM and its secretion mechanism. The paper investigates flagellar structural genes required for FlgM secretion (FliF, FliG, FliO, FliP, FliQ, FliR, FlhA, FlhB, FliK) but makes no mention of swrD or its synonym ylzI. This annotation should be removed as it attributes experimental evidence from a paper that does not study or mention SwrD. Supporting Evidence: PMID:25313396 FlgM is secreted by the flagellar export apparatus in Bacillus subtilis. |
| GO:0071977 bacterial-type flagellum-dependent swimming motility | IMP PMID:29061663 SwrD (YlzI) Promotes Swarming in Bacillus subtilis by Increa... | NEW | Summary: SwrD affects swimming motility as well as swarming. Hall et al. (2018) demonstrated that swrD deletion reduces swimming speed approximately 2-fold (from ~30 um/s to ~15 um/s). This annotation captures the effect on swimming that is distinct from swarming. Reason: While swrD mutants can still swim (unlike swarming which is abolished), their swimming is significantly impaired. The ~2-fold reduction in swimming speed and ~6-fold reduction in torque demonstrates that SwrD positively affects flagellum-dependent swimming motility. This annotation would complement the swarming annotation by capturing the broader motility phenotype. Evidence is IMP based on mutant phenotype analysis. Supporting Evidence: PMID:29061663 Mutation of swrD reduced swimming speed and torque of tethered flagella, and all swrD-related phenotypes were restored when the stator subunits MotA and MotB were overexpressed either by spontaneous suppressor mutations or by artificial induction. PMID:29061663 cells mutated for swrD swim with reduced speed |
| GO:1902021 regulation of bacterial-type flagellum-dependent cell motility | IMP PMID:29061663 SwrD (YlzI) Promotes Swarming in Bacillus subtilis by Increa... | NEW | Summary: SwrD functions as a positive regulator of flagellar motor power, modulating motility by enhancing stator activity. This regulatory function is distinct from direct involvement in motility per se. Reason: SwrD regulates the power output of the flagellar motor by acting at the level of MotAB stator activity, without affecting stator protein levels or flagellar number. This is a regulatory function that modulates the rate/extent of cell motility. The fact that MotAB overexpression rescues swrD phenotypes demonstrates that SwrD acts as a positive regulator of motor function. This GO term captures the regulatory aspect of SwrD function that the direct motility terms do not fully represent. Supporting Evidence: PMID:29061663 SwrD was not required for surfactant production, flagellar gene expression, or an increase in flagellar number. Instead, SwrD was required to increase flagellar power. PMID:29061663 all swrD-related phenotypes were restored when the stator subunits MotA and MotB were overexpressed |
| GO:0003674 molecular_function | NAS | NEW | Summary: Added to align core_functions with existing annotations. Reason: Core function term not present in existing_annotations. |
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Download this section (compressed HTML)Q: What is the molecular mechanism by which SwrD enhances MotAB stator activity?
Q: Does SwrD directly interact with MotAB stator proteins or other motor components?
Q: What is the subcellular localization of SwrD (cytoplasmic, membrane-associated, or motor-localized)?
Q: Is SwrD function regulated during the transition from swimming to swarming?
Experiment: Protein-protein interaction studies (co-IP, bacterial two-hybrid) to identify SwrD binding partners
Hypothesis: SwrD may directly interact with MotAB stator complex or other motor components
Experiment: Fluorescent tagging of SwrD to determine subcellular localization
Hypothesis: SwrD may localize to the flagellar motor or membrane
Experiment: Single-molecule fluorescence microscopy of MotA-GFP in swrD mutant vs wild-type to assess stator dynamics
Hypothesis: SwrD may reduce stator dynamism by facilitating stator retention at the motor
Experiment: Cryo-EM of motor complexes with and without SwrD to identify structural changes
Hypothesis: SwrD may induce conformational changes in the stator-rotor interface
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