Domain: Healthcare — Microbiology-Immunology
Target concept: Bacillus subtilis Detection (Starch-Iodine Colorimetric Method)

Video generation prompt: Inoculate Bacillus subtilis onto the surface of starch agar using a sterile loop in a straight line. Incubate at 37°C for 24 hours. After incubation, add iodine solution to the agar surface using a pipette, ensuring complete coverage. Observe changes on the agar surface after reagent addition.

Evaluation guide:
(i) Target concept: Enzymatic starch hydrolysis by Bacillus subtilis detected via iodine-starch colorimetry.
Minimum mechanism: Starch must be uniformly embedded in agar matrix; Bacillus subtilis must be viable and amylase-positive; iodine must be aqueous I₂/KI solution; hydrolysis must occur during incubation to deplete local starch prior to iodine exposure.
(ii)Storyline: [Frame 1–3] Sterile loop contacts culture → transfers cells → deposits straight line on agar surface. [Frame 4–6] Static agar plate (no motion) implies completed incubation. [Frame 7–9] Pipette tip approaches agar, contacts surface, dispenses iodine liquid that flows to cover line + adjacent area. [Frame 10] Immediate visual contrast emerges: linear clear zone on dark blue-black background. All events occur from fixed overhead or oblique angle; inoculated line and iodine coverage must remain fully visible and unoccluded throughout.

Manual:
Experimental Procedure
1. Sterile loop picks up Bacillus subtilis culture.
2. Loop inoculates the surface of starch agar in a single straight line.
3. Plate incubated (implied: 37°C, 24h).
4. Iodine solution added via pipette to cover inoculated line and surrounding agar.
Observation of Experimental Phenomena
After iodine addition: inoculated line appears clear/translucent against uniform dark blue-black agar background.
Summary of Experimental Principles
Bacillus subtilis secretes α-amylase, hydrolyzing starch in agar; absence of starch prevents iodine complex formation → clear zone forms along growth line.

Prompt Grounding rubric:
level_1: No sterile loop is shown; no Bacillus subtilis culture is inoculated onto the agar; no iodine solution is applied; no starch agar plate is shown; none of the four key actions (inoculating the line, incubating, adding iodine, observing the surface) are depicted.
level_2: At least one correct object is present (e.g., an agar plate or a loop), but none of the actions are carried out correctly: no straight inoculation line is shown, no pipette is used to add iodine, nothing implies the plate sat through an incubation period, and no iodine coverage of the agar is shown.
level_3: All four objects are present — the starch agar plate, the sterile loop, the Bacillus subtilis culture, and the iodine solution in a pipette; a straight-line inoculation is visible on the agar surface; the pipette tip contacts the agar; iodine solution is visibly dispensed onto the agar; nothing in the shot shows the incubation step directly (no time-lapse or on-screen label), but the sequence implies it already happened.
level_4: Everything required for score 3 holds, and in addition the incubation is visually believable: the agar surface looks uniform, moist, and undisturbed just before the iodine is added, with no fresh-looking streaks or condensation that would look wrong for a plate that sat at 37°C for 24 hours; the pipette delivers iodine across the whole length of the inoculated line, not just part of it; the inoculation line stays crisp and unblurred right up until the iodine touches it.
level_5: Everything required for score 4 holds, and in addition the same agar plate stays fully in frame from start to finish; the loop looks clean, with a plain metallic sheen and no visible residue; the pipette delivers the iodine in one smooth motion that covers only the inoculated line and the agar immediately around it, without any liquid running off the edge of the plate or splashing; the inoculation line itself is straight, unbroken, and stays fully on the agar surface, never touching the plate's rim or lifting into the air.

Scientific and Causal Correctness rubric:
level_1: No color change is seen anywhere after the iodine is applied; the agar stays a uniform amber/brown color before and after; there's no visible difference between the inoculated line and the rest of the plate; nothing suggesting starch has been broken down appears.
level_2: Iodine is applied, but the color change is not tied to the inoculation line: the whole plate turns a uniform dark blue-black, or the whole plate stays brown, with the inoculated line impossible to pick out from the background; nothing points to starch having been hydrolyzed only along the line.
level_3: A color change happens specifically along the inoculated line: that strip looks clear or noticeably lighter against a dark blue-black background everywhere else on the plate, consistent with Bacillus subtilis breaking down the starch it grew on.
level_4: Everything required for score 3 holds, and in addition the contrast is sharp and complete: the line itself shows essentially no blue-black color (translucent, pale, or whitish), while the rest of the plate is fully and evenly dark blue-black, with no partial staining, streaking, or blotchy in-between areas inside the clear strip.
level_5: Everything required for score 4 holds, and in addition the clear strip appears only where the straight inoculation line was drawn, matching its length and shape; no clearing shows up anywhere else on the plate; the dark blue-black background elsewhere is even and undisturbed except right along that line.

Spatiotemporal Consistency rubric:
level_1: The agar plate disappears and reappears; the loop or pipette jumps between positions with no motion connecting the frames; the lighting suddenly changes (e.g., bright to dark) partway through; the inoculation line appears already fully drawn with no loop motion shown creating it; the iodine appears all at once as a solid pool rather than being poured or dropped on.
level_2: The agar surface visibly warps or stretches; the loop or pipette moves in a way that looks physically impossible (e.g., bending at a point with no joint, or flipping orientation instantly); the iodine spreads in a way that ignores gravity or normal fluid behavior (e.g., spreading instantly in every direction, or appearing to flow upward); the inoculation line flickers or breaks apart between frames.
level_3: The agar plate stays rigid and flat throughout; the loop touches the agar and lifts away cleanly; the pipette tip approaches, touches, and pulls back from the agar smoothly; the iodine spreads as one connected film across the surface; nothing on the plate vanishes, duplicates, or changes from solid to liquid or back.
level_4: Everything required for score 3 holds, and in addition the whole sequence plays without jump cuts: the inoculation motion is unbroken, the iodine is dispensed without skipped frames, the lighting and the direction of shadows stay the same throughout, and the agar's texture and sheen look the same before, during, and after the iodine is added.
level_5: Everything required for score 4 holds, and in addition the inoculation line keeps the same position and angle relative to the plate's edge in every frame; the pipette tip never blocks the view of the line while dispensing; the iodine film advances steadily and evenly along the line without skipping ahead, reversing, or pausing partway; the camera view doesn't drift or shift at any point.