Domain: Natural Science — Microbiology
Target concept: Staphylococcus is positive for citrate utilization, with the medium remaining green (negative).

Video generation prompt: Staphylococcus was inoculated into citrate agar, and the resulting color of the agar was photographed after incubation at 37°C.

Evaluation guide:
(i) Target concept: Visual demonstration that Staphylococcus fails to metabolize citrate, resulting in no pH rise and no color change in Simmons citrate agar.
Minimum mechanism: Bromothymol blue must be present as indicator; citrate must be sole carbon source; alkaline shift (pH >7.6) required for blue color; Staphylococcus must lack citrate permease and enzymes for citrate catabolism.
(ii)Storyline: [Shot 1] Loop approaches and contacts agar slant surface → [Shot 2] Incubation context established (static tube in labeled environment or time-lapse cue) → [Shot 3] Same tube, same angle, same lighting, agar surface fully visible and uniformly green. All shots maintain fixed viewpoint, consistent tube orientation, and uninterrupted spatial continuity. No cutaway to unrelated objects; no insertion of non-inoculated control unless explicitly paired and labeled. Visibility constraint: Agar slant surface must occupy dominant visual area in final shot, unobscured by condensation, fingerprints, or reflections.

Manual:
Experimental Procedure
1. Sterile inoculating loop touches surface of Simmons citrate agar slant.
2. Tube incubated at 37°C for ≥24h.
3. Post-incubation, photograph agar surface.
Observation of Experimental Phenomena
Agar surface remains uniformly green; no blue color develops; no visible growth on surface.
Summary of Experimental Principles
Staphylococcus is citrate-negative: it cannot utilize citrate as sole carbon source, so bromothymol blue indicator remains protonated → medium stays green.

Prompt Grounding rubric:
level_1: No citrate-agar tube is shown; no Staphylococcus inoculation action appears; there is no incubation cue; there is no shot of the agar surface after incubation.
level_2: A single agar tube appears, but no loop-to-agar contact is shown; there is no cue that any incubation period passed; the agar surface is never clearly shown or is blocked from view.
level_3: A single citrate-agar tube is clearly visible; a sterile inoculating loop is shown touching the agar surface; an incubation cue is present (e.g., a '37°C' label, or the tube shown in an incubator-like setting); a later shot shows the agar surface after that incubation period.
level_4: Everything in score 3 holds, and the tube is clearly labeled or otherwise identifiable as Simmons citrate agar; the loop is shown touching the slant surface itself (not the tube's neck or open air); the incubation cue is unambiguous (e.g., a visible timer reading roughly a day, or a clear incubator setting); the agar surface takes up most of the final frame and stays in focus.
level_5: Everything in score 4 holds, and the tube keeps the same orientation across the inoculation shot and the later observation shot (no unexplained rotation or flip); the inoculation motion is shown as one continuous action (loop approaching, touching, then withdrawing) without a cut in the middle; the final shot of the agar surface uses the same tube, angle, and lighting as before, with nothing suggesting the tube was swapped or moved out of frame and back.

Scientific and Causal Correctness rubric:
level_1: The agar surface shows any color besides green (blue, teal, purple, or yellow), or no color is visible at all, or a color is shown changing without any inoculation ever having been shown first.
level_2: The agar looks green overall but something about the shot undercuts the reading: visible surface growth, cloudiness, cracking, or condensation obscures much of the surface; or part of the surface looks green while another part looks blue, so there is no single clear reading of 'unchanged'.
level_3: The agar surface is a consistent green across its visible area; no part of it looks blue; there is no growth pattern shown on the surface that would suggest metabolic activity; the green color is present in both the inoculation-adjacent shot and the later observation shot.
level_4: Everything in score 3 holds, and the green looks like the same shade and evenness across the whole slant, without one part looking lighter, darker, or patchier than another; nothing on the surface (bubbles, scratches, smudges) reads as a color change; the shot makes clear this same tube stayed green through the whole visible timeline, without ever dipping toward blue at any point.
level_5: Everything in score 4 holds, and the green stays visually identical from the first shot after incubation to the last, without fading, brightening, or shifting hue at any point; nothing in the timing suggests the color appeared before a plausible incubation period could have passed; the shade of green looks like a typical, recognizable Simmons citrate baseline rather than an unusual tint.

Spatiotemporal Consistency rubric:
level_1: The tube vanishes from one shot and turns up again in another spot; the loop jumps straight from off-screen onto the agar surface with no travel motion shown; the lighting swings from bright to dark between consecutive shots with no cause; the agar's slanted surface suddenly looks flat or inverted with nothing explaining the change.
level_2: The tube's position shifts by a noticeable fraction of its height between shots with no camera movement to justify it; the loop's contact point on the agar jumps to a different spot with no motion connecting the two; the direction the shadows fall changes between shots; background elements appear to jump in size or position from one shot to the next.
level_3: The tube stays in a fixed spot throughout; the loop's motion is one continuous path from entering the frame, to touching the agar, to pulling away; the slant's angle and curve look the same in every shot; the overall brightness and light direction stay consistent; nothing overlaps or passes through another object in a way that looks wrong.
level_4: Everything in score 3 holds, and the camera itself does not pan, tilt, or zoom; the tube does not rotate or tilt between shots; the loop keeps a consistent angle relative to the tube as it moves; any shadow the loop casts lines up sensibly with where the light seems to be coming from, in every shot.
level_5: Everything in score 4 holds, and the motion throughout looks smooth and physically ordinary: no sudden strobing, no warping, no moment where something visibly speeds up or slows down unnaturally; the agar's surface texture looks the same and stays clear (not smeared or blurred) while anything is moving near it; the tube and agar never look bent, cracked, or otherwise structurally different from shot to shot.