Electron Micrograph Morphology: Four Classic Silhouettes
Original bench-card visual for reviewing classic negative-stain electron micrograph shapes used as morphology anchors: rotavirus wheel, coronavirus corona, adenovirus icosahedron, and small round structured virus.
EM viral morphology: read the silhouette, then confirm
Negative-stain EM gives a shape clue, not a final identification. Use the outline as a study anchor and confirm with antigen, molecular, or SOP-directed methods.
About 70 nm wheel ("rota" = wheel). Short capsomere spokes radiate from a hub, giving a cartwheel rim. Pair the shape with stool antigen or molecular testing.
Pleomorphic enveloped particle with a fringe of club-shaped peplomers ("solar corona"). Spikes carry knobbed tips. Confirm with the respiratory molecular workflow.
About 70-90 nm, sharp hexagonal (icosahedral) outline with 20 facets; fibers may project from vertices. Use morphology as an anchor, then confirm.
About 27-32 nm. "Small round structured" outline with feathery rim and cup-like surface hollows (calicivirus family). Stool molecular testing confirms.
About 70 nm wheel ("rota" = wheel). Short capsomere spokes radiate from a hub, giving a cartwheel rim. Pair the shape with stool antigen or molecular testing.
Pleomorphic enveloped particle with a fringe of club-shaped peplomers ("solar corona"). Spikes carry knobbed tips. Confirm with the respiratory molecular workflow.
About 70-90 nm, sharp hexagonal (icosahedral) outline with 20 facets; fibers may project from vertices. Use morphology as an anchor, then confirm.
About 27-32 nm. "Small round structured" outline with feathery rim and cup-like surface hollows (calicivirus family). Stool molecular testing confirms.
What to look for by silhouette
| Visual clue | Meaning | Student shorthand |
|---|---|---|
| Wheel with radiating short spokes | Rotavirus pattern | Cartwheel rim; correlate with stool antigen or molecular result |
| Fringe of club-shaped spikes | Coronavirus pattern | Solar-corona envelope; correlate with respiratory molecular testing |
| Sharp hexagonal capsid | Adenovirus pattern | Icosahedral facets; vertex fibers may be visible |
| Small round, feathery cup-pitted surface | Small round structured virus | Calicivirus/norovirus look; confirm by molecular stool testing |
EM morphology study interpretation guide
| Pattern | What to call it | How to think about it |
|---|---|---|
| Wheel silhouette | Rotavirus-type morphology | Correlate with gastroenteritis antigen or molecular workup |
| Corona of spikes | Coronavirus-type morphology | Correlate with respiratory molecular workflow |
| Hexagonal capsid | Adenovirus-type morphology | Correlate with respiratory, ocular, or enteric context |
| Small round pitted particle | Norovirus-type morphology | Correlate with outbreak or molecular stool testing |
- Anchor each virus to one silhouette: wheel, corona, hexagon, pitted sphere.
- EM gives morphology, not a strain or serotype.
- Always close the loop with a confirmatory method.
EM is a shape clue: rota = wheel, corona = crown, adeno = hexagon, noro = pitted sphere.