Research method
Confocal Microscopy
8 studies
Confocal microscopy optically sections a fluorescent sample so that out-of-focus light is rejected, producing a sharp 3D localisation of tagged proteins, polarity markers, or labelled vesicles. The output is a spatial map — apical versus basal, plasmodesmata, endosomes, Golgi — not a binding constant or a proteome-wide inventory. Live confocal time-lapses add kinetics; still images do not.
Cell biologists use confocal imaging when the question is where a protein or particle sits and whether that location changes with polarity, knockout, or an inhibitor. It answers 'does this cargo reach this compartment?' Its main limitation is that colocalisation is not proof of a physical complex, and enteroids or cultured epithelia only approximate in-vivo tissue geometry.
Studies
8
Findings
5
7 supporting · 0 challenging · 0 qualifying citations
Open tensions
2
Currently
What we know
- Human enteroids cultured in suspension without basement-membrane extract reversed polarity within hours; β1 integrin oriented that polarity so apical surfaces became accessible for pathogen assays. Confocal polarity markers are the readout; this is not a clinical infection trial, and enteroids only approximate gut immunity.
- GFP-tagged PDLP1 family proteins targeted plasmodesmata across plant species; PDLP1a has a cytoplasmic C-tail and apoplastic DUF26 domains, and combined knockouts increased GFP cell-to-cell movement. Localisation here is a trafficking address, not a complete plasmodesmal proteome.
- Bacteroides thetaiotaomicron outer-membrane vesicles were taken up by intestinal epithelial cells and organoids within about 15 minutes, mainly by dynamin-dependent endocytosis or macropinocytosis, then reached Golgi/ER/nucleus routes and accumulated in lysosomes. Live imaging plus organelle markers and endocytosis inhibitors supplied that itinerary; systemic human effects are not proven.
- Probiotic and commensal E. coli OMVs carry peptidoglycan ligands for NOD1/NOD2 and modulate epithelial innate responses and barrier function across mucus. Imaging of vesicle–epithelium contact supports a communication route; it is not a full clinical probiotic trial.
- Several confocal-tagged papers use imaging only as a supporting localisation. APEX2 defined 22 OMM and 72 ERM cytosol-facing proteins by mass spectrometry; caveolar-coat work is biochemical stoichiometry plus ultrastructure (caveolin–cavin complex excluding EHD2/pacsin 2); N and TMV p50 were cytoplasmic in N. benthamiana with TIR-dependent association and HR in two days. Those localisation notes are not confocal trafficking movies.
Largest unresolved question
Confocal is used here for polarity reversal (enteroids), plasmodesmal targeting (PDLP), and vesicle itineraries (Bt OMVs in ~15 min; E. coli OMVs to NOD sensors). Those are different spatial questions — which face of an epithelium, which plant cell-wall channel, which endocytic route — and cannot be pooled as one 'trafficking phenotype'.
Procedure
How it works
The main stages of the method. Specific protocols and analysis choices vary between studies.
Label the sample
A fluorescent protein, dye, or antibody marks cargo, polarity, or vesicles. What is visible later is what was labelled and still fluorescent after mounting; unlabelled partners stay dark.
Scan a focused laser plane
A confocal pinhole rejects out-of-focus light so each optical section is sharp. The instrument builds a 3D localisation — apical versus basal, plasmodesmata, endosomes, Golgi — not a binding constant.
Collect stills or a time-lapse
Still images report where the signal sat at fixation or at one live frame. Time-lapses add kinetics; a single slice cannot.
Ask whether cargo reached a compartment
Papers use confocal for polarity reversal, plasmodesmal targeting, or vesicle itineraries. Overlap of two colours is a spatial hypothesis, not a purified complex.
Do not treat a slice as a tissue or a complex
Confocal answers whether this cargo reached this compartment in this sample. Colocalisation is not proof of a physical complex, and enteroids or cultured epithelia only approximate in-vivo tissue geometry.
Common misconceptions
If two fluorescent signals overlap on a confocal slice, the proteins form a biochemical complex.
PDLP GFP marks plasmodesmata and Bt OMVs colocalise with organelle markers along an endocytic route. Overlap is a spatial hypothesis; caveolar biochemistry was needed to show caveolin–cavin as one complex excluding EHD2/pacsin 2.
Apical-out enteroids are a human gut, so pathogen binding there is a clinical infection result.
Polarity reversed within hours without BME and β1 integrin oriented the apical face for pathogen assays. Enteroids approximate gut epithelium; the paper is not a clinical infection trial.
Uptake of Bt OMVs within 15 minutes means the vesicles have been shown to act systemically in people.
The itinerary (dynamin-dependent endocytosis or macropinocytosis, then Golgi/ER/nucleus routes and lysosomes) is in epithelial cells and organoids. In-vivo systemic effects in humans are not proven.
Related
Claim ledger
What the evidence shows
Drawn from 8 studies in this library. Mix labels say which citation roles are present; they are not a strength score. Supports means evidence for a finding; Challenges means evidence against a stated position; Qualifies marks scope.
Human enteroids cultured in suspension without basement-membrane extract reversed polarity within hours; β1 integrin oriented that polarity so apical surfaces became accessible for pathogen assays. Confocal polarity markers are the readout; this is not a clinical infection trial, and enteroids only approximate gut immunity.
GFP-tagged PDLP1 family proteins targeted plasmodesmata across plant species; PDLP1a has a cytoplasmic C-tail and apoplastic DUF26 domains, and combined knockouts increased GFP cell-to-cell movement. Localisation here is a trafficking address, not a complete plasmodesmal proteome.
Bacteroides thetaiotaomicron outer-membrane vesicles were taken up by intestinal epithelial cells and organoids within about 15 minutes, mainly by dynamin-dependent endocytosis or macropinocytosis, then reached Golgi/ER/nucleus routes and accumulated in lysosomes. Live imaging plus organelle markers and endocytosis inhibitors supplied that itinerary; systemic human effects are not proven.
Probiotic and commensal E. coli OMVs carry peptidoglycan ligands for NOD1/NOD2 and modulate epithelial innate responses and barrier function across mucus. Imaging of vesicle–epithelium contact supports a communication route; it is not a full clinical probiotic trial.
Several confocal-tagged papers use imaging only as a supporting localisation. APEX2 defined 22 OMM and 72 ERM cytosol-facing proteins by mass spectrometry; caveolar-coat work is biochemical stoichiometry plus ultrastructure (caveolin–cavin complex excluding EHD2/pacsin 2); N and TMV p50 were cytoplasmic in N. benthamiana with TIR-dependent association and HR in two days. Those localisation notes are not confocal trafficking movies.
- Mapping the faces of mitochondria and ER
- What proteins build the caveolar coat?
- Plant TIR domain binds viral elicitor
Study Role Design N Population Outcome Mapping the faces of mitochondria and ER Supports Animal / in-vitroAPEX2 proximity labeling of cytosol-facing OMM and ER membranes in living HEK 293T cells SILAC proteomic maps with two replicates per membrane — cell-resource study HEK 293T cells expressing OMM/ERM APEX2 fusions Proteomes of cytosol-facing outer mitochondrial and ER membranes What proteins build the caveolar coat? Supports Animal / in-vitroBiochemical purification and ultrastructure of caveolar coat proteins Structural/biochemical coat stoichiometry study — no single sample N Caveolar coat complexes (caveolins/cavins) Molecular composition and ultrastructure of the caveolar coat Plant TIR domain binds viral elicitor Supports Animal / in-vitroCo-expression domain mapping of N and TMV p50 in N. benthamiana Plant molecular genetics / protein-association assays — no single sample N Nicotiana benthamiana expressing tagged N and TMV p50 TIR-domain requirement for N–p50 association and HR cell death
Debates
Tensions and limits
Some items are genuine disagreements on the same question. Others mark different assays, populations, or outcomes.
Confocal is used here for polarity reversal (enteroids), plasmodesmal targeting (PDLP), and vesicle itineraries (Bt OMVs in ~15 min; E. coli OMVs to NOD sensors). Those are different spatial questions — which face of an epithelium, which plant cell-wall channel, which endocytic route — and cannot be pooled as one 'trafficking phenotype'.
Confocal is used here for polarity reversal (enteroids), plasmodesmal targeting (PDLP), and vesicle itineraries (Bt OMVs in ~15 min; E. coli OMVs to NOD sensors). Those are different spatial questions — which face of an epithelium, which plant cell-wall channel, which endocytic route — and cannot be pooled as one 'trafficking phenotype'.
- Apical-out enteroids for pathogen access
- How do proteins find plasmodesmata?
- How do gut-bacteria vesicles enter host cells?
- How do E. coli vesicles talk to gut epithelium?
Study Role Design N Population Outcome Apical-out enteroids for pathogen access Supports Animal / in-vitroHuman enteroids cultured in suspension without BME to reverse polarity for apical pathogen assays Enteroid lines from multiple donors; assays often scored ~10 enteroids per well across experiments — no single primary N Human intestinal enteroids β1-integrin–dependent epithelial polarity orientation for host–pathogen assays How do proteins find plasmodesmata? Supports Animal / in-vitroGFP localization and topology/knockout assays of PDLP plasmodesmal proteins Plant cell-biology localization and trafficking assays — no single sample N Arabidopsis and other plants expressing PDLP family proteins Plasmodesmal targeting of PDLPs and effects on cell-to-cell GFP movement How do gut-bacteria vesicles enter host cells? Supports Animal / in-vitroLive imaging of B. thetaiotaomicron OMVs on intestinal epithelial cells/organoids Cell/organoid trafficking assays — no single primary analytic N in stored text Intestinal epithelial cells and organoids exposed to Bt OMVs Uptake routes and intracellular biodistribution of bacterial OMVs How do E. coli vesicles talk to gut epithelium? Supports Animal / in-vitroOMVs from probiotic/commensal E. coli tested on intestinal epithelial innate sensors (NOD1) Caco-2/HT-29 cell assays — no single primary analytic N Human intestinal epithelial cell lines exposed to E. coli OMVs NOD1-dependent epithelial innate responses to bacterial OMVs
PaperFren reads this as a limit on how far one study travels — different assays, populations, or outcomes — not a forced fight between papers.
APEX2, caveolar ultrastructure, and plant TIR–p50 association are weaker confocal examples: proximity biotinylation, electron-microscopy-scale coat structure, and cytoplasmic HR biochemistry. Citing them as confocal method papers overstates the imaging.
APEX2, caveolar ultrastructure, and plant TIR–p50 association are weaker confocal examples: proximity biotinylation, electron-microscopy-scale coat structure, and cytoplasmic HR biochemistry. Citing them as confocal method papers overstates the imaging.
- Mapping the faces of mitochondria and ER
- What proteins build the caveolar coat?
- Plant TIR domain binds viral elicitor
Study Role Design N Population Outcome Mapping the faces of mitochondria and ER Supports Animal / in-vitroAPEX2 proximity labeling of cytosol-facing OMM and ER membranes in living HEK 293T cells SILAC proteomic maps with two replicates per membrane — cell-resource study HEK 293T cells expressing OMM/ERM APEX2 fusions Proteomes of cytosol-facing outer mitochondrial and ER membranes What proteins build the caveolar coat? Supports Animal / in-vitroBiochemical purification and ultrastructure of caveolar coat proteins Structural/biochemical coat stoichiometry study — no single sample N Caveolar coat complexes (caveolins/cavins) Molecular composition and ultrastructure of the caveolar coat Plant TIR domain binds viral elicitor Supports Animal / in-vitroCo-expression domain mapping of N and TMV p50 in N. benthamiana Plant molecular genetics / protein-association assays — no single sample N Nicotiana benthamiana expressing tagged N and TMV p50 TIR-domain requirement for N–p50 association and HR cell death
PaperFren reads this as a limit on how far one study travels — different assays, populations, or outcomes — not a forced fight between papers.
Timeline
How understanding moved
Study years are when the paper was published. Evidence edits are dated changes to this page's claims. Explanations are when PaperFren added a Discovery — not a claim that the science happened that day.
2026
Concept page published
Confocal Microscopy
Change log
What changed
Dated edits to this page's evidence: studies added or removed from a claim, claims added or withdrawn, and new explanations tagged here. Coverage edits are distinct from reviewed research changes and corrections. Dates record PaperFren updates; study publication dates appear in the timeline.
- Coverage updated · Concept page published
Papers
8 studies in this library bear on Confocal Microscopy, ordered by citations.
- Apical-out enteroids for pathogen access
Suspending human enteroids without ECM flips polarity so microbes can meet the apical face.
- Mapping the faces of mitochondria and ER
APEX2 proximity biotinylation yields high-quality proteomic maps of cytosol-facing outer mitochondrial and ER membranes in living human cells.
- How do proteins find plasmodesmata?
PDLP1 is a type I membrane protein targeted to plasmodesmata; altering PDLP dosage changes GFP cell-to-cell trafficking.
- Plant TIR domain binds viral elicitor
Tobacco N protein’s TIR domain is critical for association with TMV p50 elicitor.
- How do gut-bacteria vesicles enter host cells?
B. thetaiotaomicron outer-membrane vesicles are taken up within minutes via dynamin-dependent endocytosis/macropinocytosis and traffic to Golgi/ER/lysosomes.
- How do E. coli vesicles talk to gut epithelium?
Outer membrane vesicles from probiotic and commensal E. coli deliver ligands that activate NOD1-mediated immune responses in intestinal epithelial cells.
- What proteins build the caveolar coat?
Caveolins and cavins purify as a caveolar coat complex with Cavin 1 as a core trimeric component.
- LN DCs shelter antibiotic-tolerant Salmonella
Slow-growing Salmonella in cecum lymph-node dendritic cells survive ciprofloxacin therapy.
Compare studies
Select 2–10 studies. Design and N are labels, not a ranking.
Nothing selected yet.
Questions
What is still open
Confocal is used here for polarity reversal (enteroids), plasmodesmal targeting (PDLP), and vesicle itineraries (Bt OMVs in ~15 min; E. coli OMVs to NOD sensors). Those are different spatial questions — which face of an epithelium, which plant cell-wall channel, which endocytic route — and cannot be pooled as one 'trafficking phenotype'.
APEX2, caveolar ultrastructure, and plant TIR–p50 association are weaker confocal examples: proximity biotinylation, electron-microscopy-scale coat structure, and cytoplasmic HR biochemistry. Citing them as confocal method papers overstates the imaging.
Ask PaperFren about Confocal Microscopy
Study this conceptflashcards and short-answer questions
Enteroid polarity reversed within hours after removing BME. Why does β1 integrin matter for a host–pathogen confocal assay?
β1 integrin oriented polarity so the apical surface faced the medium, which is the face many gut pathogens contact. Without that orientation, confocal pathogen-binding assays would score the wrong pole.
PDLP combined knockouts increase GFP movement. How does confocal localisation of PDLP1a topology (cytoplasmic C-tail, apoplastic DUF26) constrain the mechanism?
The protein is a transmembrane plasmodesmal resident with domains on both sides of the membrane, so knockouts likely change the channel environment rather than a soluble cytoplasmic GFP pump. Imaging supplies the address; the KO supplies the trafficking phenotype.
Bt OMV uptake is mainly dynamin-dependent endocytosis or macropinocytosis within ~15 min. What experimental pieces (not just pretty pictures) support that route?
Live imaging with organelle markers plus endocytosis inhibitors. Kinetics and inhibitor sensitivity distinguish those routes from a non-endocytic dump onto the plasma membrane.
E. coli OMVs carry NOD1/NOD2 peptidoglycan ligands. Why is confocal contact with epithelium still not a probiotic efficacy trial?
Imaging and innate-sensor assays show a mucus-crossing communication route that modulates epithelial responses and barrier function. Patient outcomes are not measured.