Domain: Healthcare — Microbiology-Immunology
Target concept: Yersinia enterocolitica Detection (Colorimetric Method)

Video generation prompt: Prepare test tubes containing selective enrichment broth, add the prepared Yersinia enterocolitica sample, incubate for a short period, then add a specific chromogenic reagent, gently mix, and compare the color with a control tube using a colorimetric test card.

Evaluation guide:
(i) Target concept: Enzyme-mediated chromogenic detection of viable Yersinia enterocolitica via β-galactosidase activity in selective enrichment broth.
Minimum mechanism: Chromogenic substrate must be hydrolyzed *only* by target bacterial enzyme; color development requires both reagent addition *and* enzymatic activity; control tube lacks bacteria so no hydrolysis occurs; color must emerge *after* mixing to ensure reagent-broth homogeneity.
(ii)Storyline: [Frame 0–2] Two upright, identical test tubes side-by-side in fixed viewpoint; left tube is control (clear/pale yellow liquid), right tube is sample (same initial appearance). [Frame 3–4] Chromogenic reagent bottle approaches right tube; droplet release begins. [Frame 5–6] Reagent fully dispensed into right tube; no contact with left tube. [Frame 7–8] Right tube undergoes smooth, continuous inversion mixing; liquid deforms coherently; left tube remains still. [Frame 9–10] Mixing stops; both tubes settle; right tube now shows uniform red/pink/magenta color; left tube unchanged; colorimetric test card enters frame adjacent to both tubes, aligned for direct hue comparison; final frame holds stable for visual verification.

Manual:
Experimental Procedure
1. Place two identical test tubes side-by-side: left = control (selective enrichment broth only), right = sample (broth + Yersinia enterocolitica).
2. Add chromogenic reagent to sample tube only; do not add to control.
3. Gently mix sample tube by inversion 3–5 times.
4. Compare color of sample tube to control tube using colorimetric test card.
Observation of Experimental Phenomena
Sample tube develops uniform red/pink/magenta color; control tube remains pale yellow or clear; colorimetric test card contains matching positive (red/pink/magenta) and negative (pale yellow/clear) swatches.
Summary of Experimental Principles
Yersinia enterocolitica produces β-galactosidase, which cleaves chromogenic substrate (e.g., X-Gal analog) releasing colored product; selective enrichment broth suppresses competitors while allowing target growth and enzyme expression.

Prompt Grounding rubric:
level_1: No test tubes appear, no chromogenic reagent bottle or colorimetric test card is shown, no addition of the Yersinia sample to broth is depicted, and no incubation, mixing, or side-by-side tube arrangement occurs.
level_2: A single test tube appears but not paired with a second one, or the tube(s) are empty rather than containing broth; the chromogenic reagent bottle, the sample-addition step, or the mixing action is missing altogether; the sequence of steps is scrambled or reduced to a single unexplained action.
level_3: Two upright test tubes are shown together, each containing enrichment broth; one is set up as a control, the other receives the prepared Yersinia enterocolitica sample; a chromogenic reagent bottle is held near the tubes and dispenses into one of them; a gentle mixing motion follows; a colorimetric test card is present somewhere in the shot.
level_4: All elements of score 3 are present AND the reagent is added to the sample tube only, never touching the control tube; mixing happens strictly after the reagent addition, not before or during dispensing; both tubes stay upright and in place throughout; the test card sits next to the two tubes in a position that allows a side-by-side look; no unrelated prop (gloves, timer, extra labels) crowds the shot.
level_5: All elements of score 4 are present AND the reagent bottle's contents are visibly a distinct chromogenic liquid rather than a colorless one like water or buffer; the tube that received reagent and the tube that did not remain individually trackable (never swapped or relabeled) from dispensing through the final comparison; the test card's swatches line up level with the tube menisci for a direct read; both tubes and the card sit in the same sharp focal plane with nothing blocking the view of any of them.

Scientific and Causal Correctness rubric:
level_1: Neither tube changes color: the sample tube and the control tube look identical before and after every step; if any color appears it shows up in the control tube rather than the sample tube; the test card carries no swatch relevant to a positive Yersinia result; there is no visible link between adding the reagent and any color appearing.
level_2: A color change happens, but on the wrong tube (control instead of sample, or both at once), or it happens before the reagent is added or before mixing; the resulting hue on the sample tube doesn't correspond to any biologically valid positive shade (red, pink, or magenta) for this assay.
level_3: Only the sample tube changes color, and only after the reagent has been added and the tubes have been gently mixed; the control tube keeps its original pale-yellow-to-clear appearance throughout; the test card shows at least one swatch whose hue matches the sample tube's new color; the color in the sample tube looks even from top to bottom rather than patchy.
level_4: All elements of score 3 are present AND the control tube's final color is clearly different from the sample tube's; the sample tube's liquid stays clear of cloudiness or visible precipitate that would mask its hue; the test card's swatches are close enough to the tubes to make a direct hue comparison; the sample tube never turns an implausible color for this test such as blue, green, or purple.
level_5: All elements of score 4 are present AND the sample tube's final hue lines up with one specific positive swatch on the card rather than sitting ambiguously between two swatches; the control tube's hue lines up with the card's negative/blank swatch; the color in the sample tube is uniform from the meniscus down to the tube's base; no ring of discoloration forms at the tube wall or meniscus that would throw off the color read.

Spatiotemporal Consistency rubric:
level_1: The two tubes swap positions or vanish and reappear between shots with no visible motion carrying them there; the reagent bottle appears already empty in one frame and full in the next without a dispensing action; the tube liquid's surface shows one height in one frame and a completely different height in the next with nothing bridging the change; the scene's lighting swings from bright to dim within a couple of frames; a tube's outline warps from round to oval and back.
level_2: One tube tilts past a steep angle (roughly more than 30 degrees) with nothing propping it up; the mixing motion starts and stops abruptly rather than easing in and out; ripples on the liquid surface appear or vanish with no visible cause; the test card slides or rotates out of frame partway through the comparison; the shadow the tubes cast swings to a different direction partway through with no change in the light source.
level_3: Both tubes stay upright and in the same spot for the whole sequence; the mixing motion runs smoothly from start to finish without a break; the liquid surface deforms and then settles in a continuous way as mixing proceeds; the test card stays in place and fully visible next to the tubes; the light stays even across both tubes and the card throughout.
level_4: All elements of score 3 are present AND if the camera moves at all, the two tubes shift together with no relative sliding between them; the meniscus in each tube keeps a consistent gentle curve before and after mixing; the reagent bottle keeps the same angle and distance from the sample tube while dispensing; there's no flicker or stutter making the motion look broken.
level_5: All elements of score 4 are present AND the tubes, the test card, and the bottle's path form a spatial layout that holds steady across every frame; the ripples from mixing form, spread, and die down in one continuous progression rather than skipping stages; the tube outlines and the card's grid lines stay geometrically consistent with no lens warping; the shadows the tubes and card cast point the same direction throughout, consistent with a single unmoving light source.