Domain: Healthcare — Microbiology-Immunology
Target concept: E. coli Detection

Video generation prompt: Inoculate a suitable amount of the standard *Escherichia coli* strain onto a urea broth tube containing phenol red indicator using a sterile inoculating loop, gently mix, and incubate at 37°C for 24 hours. After incubation, observe the color of the culture medium.

Evaluation guide:
(i) Target concept: Visual confirmation that standard E. coli does NOT hydrolyze urea (urease-negative phenotype), shown by the absence of a phenol red color shift in urea broth.
Minimum mechanism: Standard/reference E. coli strains (e.g., ATCC 25922) lack meaningful urease activity → urea in the broth is not hydrolyzed → no ammonia is released → broth pH stays near neutral/acidic → phenol red indicator stays in its yellow-orange protonated state → the broth's color after incubation is visually the same as before incubation. (A pink-red shift would indicate a urease-POSITIVE organism, such as Proteus mirabilis, and is NOT the expected result for E. coli.)
(ii)Storyline: [Frame 0–3s] Sterile loop contacts E. coli source (colony or drop); [Frame 3–6s] Loop enters urea broth tube and performs gentle swirling (broth visibly agitated, yellow-orange throughout); [Frame 6–7s] Tube placed into static incubation context (e.g., labeled incubator or time-lapse marker); [Frame 7–10s] Same tube reappears with broth color visually unchanged, still yellow-orange, matching its pre-incubation appearance; all transitions occur from fixed frontal viewpoint with consistent lighting; no off-screen object introduction or removal; no color change occurs anywhere in the tube.

Manual:
Experimental Procedure
1. Sterile inoculating loop touches E. coli standard strain colony/suspension.
2. Loop inserts into urea broth tube containing phenol red indicator.
3. Gentle swirling motion mixes inoculum into broth.
4. Tube incubated at 37°C for 24 hours.
Observation of Experimental Phenomena
Urea broth remains yellow-orange after incubation; no shift to pink-red occurs.
Summary of Experimental Principles
Standard/reference E. coli strains are urease-negative: they lack the enzyme needed to hydrolyze urea, so no ammonia is released and the broth's pH does not rise. Phenol red therefore stays in its yellow-orange (acidic/neutral) form. This negative result is diagnostic — it is what distinguishes E. coli from urease-positive organisms (e.g., Proteus mirabilis), whose urea hydrolysis raises the pH and turns the same indicator pink-red.

Prompt Grounding rubric:
level_1: No urea broth tube is visible, no sterile inoculating loop is visible, no E. coli source material (colony or suspension) is visible, and no incubation step is depicted; the core experimental setup is entirely absent.
level_2: At least one core object appears (tube, loop, or E. coli source), but a critical object is missing (urea broth tube absent, OR inoculating loop absent, OR E. coli source material absent), or the inoculation action (loop touching the E. coli source, then entering the tube) is not depicted at all.
level_3: Urea broth tube, sterile inoculating loop, and E. coli source material are all visibly present; the inoculation action occurs in the correct order (loop contacts E. coli source, then loop enters the tube, then a mixing motion is shown); no incubation step or post-incubation view of the tube is shown yet.
level_4: All conditions for score 3 are met, and additionally: an incubation step is depicted through a clear temporal cue (e.g., a clock/timer overlay, an on-screen “24h” or “37°C” label, or a time-lapse transition such as a fade/cut); the same urea broth tube is shown again afterward in a recognizable post-incubation view, without the tube being replaced by a visibly different tube, container, or vessel.
level_5: All conditions for score 4 are met, and additionally: the sterile loop, tube, and incubation staging are shown with no extraneous objects (no unrelated tools, hands, or labels crossing the frame that are not part of the procedure); the tube's identity, size, and label (if any) are visually consistent from the inoculation shot through to the post-incubation shot, so the viewer can confirm it is the same physical tube; no object substitution (e.g., no swap of tube type, loop type, or organism-source container) occurs at any point.

Scientific and Causal Correctness rubric:
level_1: No indicator response is depicted at all (broth shown without phenol red, or color is indeterminate throughout), or the broth undergoes a color shift to pink-red (or any other hue) after incubation, incorrectly implying that this standard E. coli strain is urease-positive; or a color change appears before inoculation, or without any E. coli ever being introduced.
level_2: Phenol red is present and initially yellow-orange, but the outcome is ambiguous or contradicts the setup: e.g., the broth shifts to an intermediate or ambiguous hue (not clearly yellow-orange and not clearly pink-red) after incubation, or the color changes and reverts inconsistently, or the sequence implies a change happened but the causal link to the (absent) urease reaction is confusing or self-contradictory.
level_3: Urea broth with phenol red indicator appears yellow-orange before inoculation; after incubation, the same tube's broth is still visibly yellow-orange: no shift toward pink or red has occurred; E. coli is shown being introduced before the incubation step; no gas bubbles, turbidity change, or other artifact is misrepresented as a positive color reaction.
level_4: All conditions for score 3 are met, and additionally: the yellow-orange color is stable and uniform throughout the broth (not just in isolated patches) both before and after incubation; no competing visual artifact (e.g., lighting shift, filter tint, or surface reflection) creates the false impression of a color change; the pre- and post-incubation shots of the broth are visually indistinguishable in hue.
level_5: All conditions for score 4 are met, and additionally: the broth's yellow-orange color is maintained uniformly across ≥90% of its visible volume with no residual pink or red patches anywhere, including near the tube wall, cap, or meniscus; if a second (control or comparison) tube is shown, only a tube actually inoculated with a genuinely urease-positive organism would show a pink-red shift; the E. coli tube itself remains yellow-orange without exception.

Spatiotemporal Consistency rubric:
level_1: Severe spatiotemporal rupture: the urea broth tube abruptly jumps position, rotates, or changes size without cause, or vanishes and reappears between frames with no motion connecting the two states; the inoculating loop appears or disappears without ever tracing a path to/from the tube; the broth's color changes in an instant mid-swirl rather than gradually over the incubation interval; the lighting or shadow on the tube jumps abruptly between the inoculation and post-incubation shots with no cause; the camera framing or background shifts discontinuously between the inoculation and post-incubation shots.
level_2: Moderate rupture: the tube's position, size, or orientation differs noticeably between the inoculation shot and the post-incubation shot without a continuous camera move to explain it; the loop's swirling motion is jerky or appears to skip the contact phase (e.g., it is already inside the broth with no insertion shown); the cut from inoculation to post-incubation lacks any linking cue (no fade, timer, or label) so the two shots feel spatially disconnected.
level_3: The same urea broth tube stays continuously identifiable across the inoculation and post-incubation views; the camera viewpoint does not pan, zoom, or rotate between the two; the loop's motion (approach, contact with the E. coli source, insertion, gentle swirl) is smooth and physically plausible; the illumination on the tube and broth looks the same in both the inoculation shot and the later shot, with no unexplained brightening, darkening, or color-cast shift.
level_4: All conditions for score 3 are met, and additionally: the tube stays in a fixed position relative to the background throughout; the loop keeps a consistent size and shape as it moves toward, into, and out of the broth; the swirling motion visibly disturbs the broth's surface (a ripple or meniscus movement) only while the loop is inside it, starting and stopping with the loop's entry and exit.
level_5: All conditions for score 4 are met, and additionally: no frame duplication, ghosting, or excess motion blur obscures the loop's entry, swirl, or exit; the broth surface shows no unexplained agitation during the incubation interval itself; the tube's fill level, meniscus position, and label orientation (if any) match exactly between the inoculation shot and the post-incubation shot, confirming it is the same tube observed continuously through time rather than a substituted double.