Domain: Healthcare — Microbiology-Immunology
Target concept: Staphylococcus epidermidis Detection (Glycerol-Phenol Red Colorimetric Method)

Video generation prompt: Inoculate a sample of Staphylococcus epidermidis into a test tube containing glycerol-phenol red broth using a sterile inoculating loop, gently mix, and then incubate the tube.

Evaluation guide:
(i) Target concept: Visual confirmation of glycerol fermentation by S. epidermidis via pH-dependent color change in phenol red medium.
Minimum mechanism: Presence of viable S. epidermidis cells transferred into glycerol-phenol red broth must initiate metabolic acid production during incubation, causing irreversible, homogeneous, and complete protonation of phenol red dye, resulting in uniform yellow coloration of the entire liquid volume.
(ii)Storyline: [Frame 0–2] Sterile loop approaches and contacts off-white S. epidermidis colony on agar surface. [Frame 3–4] Loop retracts with visible inoculum, moves in continuous arc toward tube mouth. [Frame 5–6] Loop fully enters glycerol-phenol red broth (pink/red liquid) and initiates gentle swirling motion causing coherent liquid surface deformation. [Frame 7] Loop withdraws; tube remains upright, motionless, fully visible in fixed viewpoint. [Frame 8–10] Broth transitions uniformly and completely from pink/red to bright yellow (no gradient, no delay, no partial change), confirming acid production. All events occur within single fixed camera view; no cuts, no perspective shifts, no object occlusion violating spatial continuity.

Manual:
Experimental Procedure
1. Flame-sterilize inoculating loop; cool briefly.
2. Touch off-white Staphylococcus epidermidis colony on agar plate with loop.
3. Insert loop into glycerol-phenol red broth tube; gently swirl to mix.
4. Place tube upright in incubator.
Observation of Experimental Phenomena
Glycerol-phenol red broth changes from pink/red to yellow after incubation — indicating acid production from glycerol fermentation by S. epidermidis.
Summary of Experimental Principles
S. epidermidis ferments glycerol, producing acid that lowers pH; phenol red indicator shifts from pink/red (pH ≥8.2) to yellow (pH ≤6.8).

Prompt Grounding rubric:
level_1: No sterile inoculating loop visible; no test tube containing glycerol-phenol red broth present; no Staphylococcus epidermidis sample shown (e.g., no colony on agar or suspension); no inoculation action occurs; no mixing or incubation implied.
level_2: At least one correct object present (e.g., test tube OR loop), but inoculating loop is not visibly sterile (no flame-sterilization cue or unused appearance), or tube lacks glycerol-phenol red broth label/visual identity (e.g., clear liquid with no pink/red hue, no labeling), or sample is absent/misrepresented (e.g., shown as powder, colored pellet, or unrelated organism), and no inoculation-to-mixing sequence is depicted.
level_3: Sterile inoculating loop, glycerol-phenol red broth tube, and S. epidermidis sample (e.g., small off-white colony on agar or turbid suspension) are all present; loop contacts sample and then enters tube; gentle mixing motion is shown (e.g., swirling or up-down motion of tube); incubation is implied by static tube placement in a warm environment or labeled incubator background -- but either (a) loop fails to visibly enter the tube's liquid, or (b) the mixing motion is jerky without producing any visible fluid agitation, or (c) tube orientation changes abruptly mid-action, breaking the fixed viewpoint.
level_4: All objects are correctly present and visually identifiable: the sterile loop (shiny, residue-free, straight, no visible bending), the glycerol-phenol red broth tube (a transparent tube holding a distinct pink-to-red liquid, labeled or otherwise contextually unambiguous), and the S. epidermidis sample (a small circular off-white colony on the agar surface, or a uniform faint turbidity in suspension); the loop contacts the sample, then enters the tube's liquid, then performs a visible swirling or up-and-down mixing motion; the tube is shown upright and does not change into a different container or move to a different spot on the bench between the start and end of the sequence; incubation is implied by the tube being shown at rest in a consistent, recognizable thermal context (e.g., an incubator shelf or a labeled warm setting); only one non-core flaw is present, such as the tube's label being illegible while its identity is still unambiguous from color, shape, and context, or the agar colony having a slightly irregular outline while still clearly reading as a single bacterial colony.
level_5: Everything required at level 4 holds, AND every core object keeps a fully correct, unambiguous visual identity throughout: the loop never resembles a different tool (e.g., a swab or a spatula), the broth tube is never confused with a different container or a different-colored liquid, and the colony or suspension never takes on a different organism's morphology (e.g., never shown as filamentous, pigmented, or arranged in chains); the tube's starting pink/red color, the loop's clean and sterile appearance, and the incubator or warm-setting context are all fully consistent with the intended setup from the first moment of the sequence to the last.

Scientific and Causal Correctness rubric:
level_1: The broth's liquid color never shifts toward yellow at all, remaining colorless, blue, already yellow, green, or purple throughout instead of starting from the expected pink/red baseline; no liquid is even visible (e.g., a solid gel, dry powder, or vapor stands in for the broth); no causal link is shown between the inoculation action and any visual outcome; S. epidermidis is misrepresented as pigmented (e.g., golden or black) or shown with the wrong morphology (e.g., arranged in chains, rod-shaped, or forming spores).
level_2: Broth shows incorrect baseline color (e.g., yellow or blue instead of pink/red); S. epidermidis sample appears as Gram-negative rod or fungal hyphae; mixing action shown but no liquid motion visible; no color transition occurs and no time-resolved incubation effect shown; or color change occurs without prior inoculation/mixing.
level_3: Glycerol-phenol red broth starts pink/red (correct baseline); S. epidermidis sample is off-white, circular, and microcolonial (not confluent); inoculation and mixing occur; after a static incubation phase, broth color changes from pink/red to yellow -- but the change is incomplete (e.g., only the top layer yellow, patchy), or appears before mixing completes, or occurs without a visible static incubation period, or the yellow region lacks a sharp boundary with residual pink.
level_4: Broth begins uniformly pink/red; S. epidermidis sample is off-white, discrete, and consistent with staphylococcal morphology; inoculation → mixing → static incubation sequence is intact; broth transitions fully and uniformly from pink/red to yellow during the incubation phase; the yellow color is homogeneous, stable, and occupies the entire liquid volume -- only one non-core flaw: e.g., a slight residual pink meniscus rim, or a minor transient bubble cloud obscuring part of the color field during transition.
level_5: Broth is uniformly pink/red at start; S. epidermidis sample is a single, small, off-white, convex, non-pigmented colony on agar (or identical turbidity in suspension); loop transfers sample into the broth; mixing produces visible fluid motion; tube rests undisturbed in fixed viewpoint; broth undergoes complete and homogeneous color transition from pink/red to bright yellow across the entire liquid volume during incubation -- no gradient, no streaks, no residual pink, no bubbles, no delay, no reversal.

Spatiotemporal Consistency rubric:
level_1: The test tube is visible one moment, completely missing from the frame the next, and then simply back in view again with no visible cause; the loop jumps directly from touching the colony to being fully inside the tube, with no visible path connecting the two moments; the broth liquid vanishes during the mixing motion and then reappears; the scene's brightness changes drastically within a single continuous shot, with no cut to explain it; the tube rotates a quarter turn or more with nothing visibly causing or carrying that rotation; the background changes to a completely different setting between one frame and the next.
level_2: The loop or the tube flickers in and out of visibility across a few frames; the broth's liquid surface freezes in place during the swirling motion and then suddenly jumps to a different shape; the hand holding the loop enters the frame with no visible forearm or wrist leading into it; the tube wobbles or tips sharply with no corresponding push or contact to explain it; the swirling motion starts or stops instantly with no visible acceleration or deceleration.
level_3: The loop, the tube, and the colony or suspension all stay continuously present and in their expected positions; the loop moves along a continuous path from the colony into the tube; the liquid's surface motion begins only once the loop enters and continues smoothly through the mixing action; the tube stays upright and does not shift position on the bench; minor flaws are still present, such as the loop appearing to merge slightly with the tube's rim for a moment without a clear sense of depth, or the swirling pattern on the liquid surface not quite matching the direction of the loop's motion, or the visible background behind the tube looking a little different in brightness between the inoculation and the incubation portions of the sequence.
level_4: Everything required at level 3 holds, AND the loop's path from the colony to the tube mouth is a single smooth arc with no sudden changes in direction; the liquid's motion during swirling matches the timing and direction of the loop's own movement; the tube does not change position or orientation once it is set down for incubation; only one minor flaw remains, such as a brief flare of reflected light off the tube's glass momentarily obscuring the loop tip as it enters, or the tube appearing to hold very slightly still rather than perfectly motionless during the incubation shot.
level_5: Everything required at level 4 holds, AND the loop's motion from first touching the colony to full insertion in the broth is one unbroken, continuous trajectory; the liquid responds immediately to the swirling motion with a coherent surface disturbance that settles naturally once the mixing stops; the tube stays rigidly upright and fixed in the same spot on the bench for the entire sequence; the loop, the tube, the colony, and the broth all remain visible without any of them flickering, freezing, or being unexpectedly hidden from view at any point.