Domain: Healthcare — Microbiology-Immunology
Target concept: Enterobacter aerogenes Detection (Lactose–Citrate Colorimetric Method)

Video generation prompt: Inoculate Enterobacter aerogenes onto a lactose fermentation medium and incubate, then transfer to a citrate medium.

Evaluation guide:
(i) Target concept: Visual verification of Enterobacter aerogenes biochemical identity via sequential lactose fermentation and citrate utilization assays.
Minimum mechanism: Growth must occur before color change in each medium; color change must be spatially confined to growth sites; citrate blue requires prior growth and cannot precede it; lactose pink must co-occur with growth and cannot appear without it.
(ii)Storyline: Frame 1–3: Loop approaches and inoculates lactose medium surface → growth emerges (turbidity/colonies) → pink/red color appears *only where growth is*. Frame 4–6: Loop lifts, moves continuously to citrate medium → contacts surface → growth emerges (delayed relative to lactose) → blue color appears *only where growth is*, with no blue in blank regions. All events occur in fixed viewpoint, side-by-side or vertically stacked media, with no camera repositioning, lighting shift, or object substitution.

Manual:
Experimental Procedure
1. Sterile loop picks up Enterobacter aerogenes culture.
2. Loop streaks the lactose fermentation medium (MacConkey agar, whose pH indicator is neutral red).
3. Growth (turbidity/colonies) and the resulting acid-driven color change develop visibly on the lactose medium over the course of incubation, shown as a continuous or time-lapsed on-screen process.
4. Loop transfers growth from the lactose medium to the citrate medium (Simmons citrate agar).
5. Growth and the resulting alkaline-driven color change develop visibly on the citrate medium over the course of incubation, shown as a continuous or time-lapsed on-screen process.
Observation of Experimental Phenomena
- Lactose medium: visible growth + pink/red coloration (acid from lactose fermentation lowers the medium's pH, turning the neutral red indicator pink/red).
- Citrate medium: visible growth + blue coloration (citrate utilization raises the medium's pH, turning the bromothymol blue indicator blue).
Summary of Experimental Principles
Enterobacter aerogenes is a lactose-fermenting, citrate-utilizing Gram-negative rod. Lactose fermentation produces acid, which lowers the medium's pH and turns the neutral red indicator in MacConkey agar pink/red. Citrate utilization produces alkaline byproducts that raise the medium's pH and turn the bromothymol blue indicator in Simmons citrate agar blue.

Prompt Grounding rubric:
level_1: No depiction of loop inoculation, no lactose fermentation medium (MacConkey agar), no citrate medium (Simmons citrate agar), and no transfer of the loop between them; none of the required objects or actions are identifiable.
level_2: At least one recognizable lab object (e.g., an agar plate or slant) is present, but there is no visible inoculation action, no visible transfer of the loop from one medium to the other, and the lactose-then-citrate order of the two media is not established.
level_3: Both the lactose fermentation medium (MacConkey agar) and the citrate medium (Simmons citrate agar) are visible; a loop first inoculates the lactose medium, and the same loop is then shown transferring to the citrate medium, in that order, but the two media are not clearly labeled or their spatial arrangement is ambiguous, e.g. not clearly next to each other in the same shot.
level_4: All elements of 3-score are present AND the two media are visually identifiable as MacConkey agar and Simmons citrate agar (by appearance or label), not some unrelated medium such as plain LB agar; the loop inoculates the MacConkey medium first, then transfers to the Simmons citrate medium; both media appear next to each other or clearly adjacent within a fixed shot.
level_5: All elements of 4-score are present AND both media show their correct canonical starting appearance before any growth: the MacConkey agar begins as a firm, slightly pink-tan translucent surface (its neutral red indicator's color at the medium's neutral starting pH, distinct from the deeper pink/red that develops later from fermentation), and the Simmons citrate agar begins as a green solid slant; the loop visibly inoculates the MacConkey surface, then the same loop visibly transfers material to the Simmons citrate surface; both media stay in the same fixed frame throughout, arranged next to each other or one above the other, with no unrelated tools or containers in view.

Scientific and Causal Correctness rubric:
level_1: Neither medium shows any growth or color change; there is no causal connection between the loop's inoculation and any change; or the citrate medium turns yellow or stays green without ever turning blue, contradicting Enterobacter aerogenes's known lactose-positive, citrate-positive biochemistry.
level_2: Growth appears on only one of the two media; color change is missing where growth is present, or appears where growth is absent (e.g., the lactose medium stays its original color despite visible growth, or turns pink/red with no growth present); or growth is visible on both media but neither medium's color ever changes.
level_3: Growth (turbidity or colonies) is visible on the lactose medium together with a pink/red color change indicating acid from lactose fermentation; growth and a distinct blue color change are both visible on the citrate medium, but the blue color appears before or at the same time as the growth on the citrate medium, rather than following it, violating the expected order in which growth must precede the alkaline color shift.
level_4: Growth appears first on the lactose medium, together with pink/red coloration; growth then appears on the citrate medium, followed by a clear blue color change confined to the areas with growth, with no blue in uninoculated regions; both color changes match the expected Enterobacter aerogenes phenotype (lactose-positive, citrate-positive), but the blue color may bleed slightly past the edge of growth or look slightly patchy.
level_5: Pink/red color appears only on the lactose medium and only where growth is present, with a sharp boundary between colored and uncolored agar; blue color appears only on the citrate medium and only where growth is present, with no blue, green, or yellow residue in uninoculated areas; the sequence is unambiguous (lactose growth, then lactose color change, then citrate growth, then citrate color change), with no color bleeding or haloing beyond the growth.

Spatiotemporal Consistency rubric:
level_1: Severe spatiotemporal break: the media plates or slants jump between different positions or appear/disappear across frames; the inoculation loop vanishes and reappears without completing its motion; growth or color change appears fully formed within a single frame with no visible progression; or the camera cuts to an unrelated angle mid-action.
level_2: Moderate discontinuity: the loop's motion toward or between the media has at least two visible breaks or jumps; a medium's plate or slant shifts position or rotates between shots; growth appears across more than one frame without a gradual increase in turbidity or color; or the overall scene brightness jumps sharply brighter or darker between consecutive frames with no visible cause such as a lamp switching on or off.
level_3: The loop's approach to, contact with, and lift from the lactose medium is one continuous motion, as is its later approach to and contact with the citrate medium; growth on each medium thickens gradually across frames rather than jumping to full density; the plates or slants do not shift from their spot for the rest of the shot, but one small flaw is present, such as a brief moment where the loop is hidden from view during the transfer, or the citrate slant appearing to wobble very slightly in a single frame without otherwise moving.
level_4: All elements of 3-score are present AND the loop's whole trajectory (dip into culture, streak on the lactose medium, lift, move to the citrate medium, streak) follows one uninterrupted, natural arc; growth thickens or the color change deepens step by step without ever jumping backward or skipping stages; the plates or slants and the loop stay in sharp focus and the same relative position throughout, with at most one small, clearly non-disruptive flaw allowed, such as brief motion blur on the loop tip that does not obscure which medium it is touching.
level_5: All elements of 4-score are present AND the loop's motion is fully visible and anatomically plausible at every point, with no floating or sudden speed change; the two media plates or slants stay in the exact same position and orientation throughout, with growth density and color intensity increasing in a smooth, uninterrupted progression from frame to frame; the faint reflection of the lab lighting on the clear agar surface or dish lid stays in the same relative spot on each plate unless the plate itself is moved, and the loop casts a shadow on the agar that moves together with the loop rather than jumping independently of it.