Domain: Healthcare — Medicine
Target concept: Antibacterial effect of antibiotics on bacterial culture (antimicrobial activity of the preparation)

Video generation prompt: A transparent glass bottle containing an appropriate amount of turbid bacterial culture is placed on a table. An appropriate amount of bactericidal antibiotic solution is added to the bottle, the solution is thoroughly mixed, and time-lapse observations are conducted.

Evaluation guide:
(i) Target concept: Antibiotic-induced reduction in bacterial suspension turbidity as a proxy for antimicrobial efficacy.
Minimum mechanism: Bacterial cells must be suspended (not settled) and sufficiently concentrated to produce macroscopic turbidity; the antibiotic added must be a bactericidal/lytic agent (not merely bacteriostatic), since only progressive killing and lysis of bacteria across the culture's growth cycle measurably reduces cell density; the clearing shown represents a process that in reality unfolds over hours and is depicted here as a compressed time-lapse, not an instantaneous effect of mixing.
(ii)Storyline: Phase 1 (Baseline): Static shot of transparent glass bottle on table, filled with uniformly turbid liquid (milky/opaque appearance, no sediment). Phase 2 (Intervention): Clear liquid stream enters bottle from above (antibiotic addition), followed immediately by continuous rotational/inversion motion of bottle (mixing). Phase 3 (Response, compressed time-lapse over hours): Turbidity progressively declines as the bactericidal antibiotic lyses bacteria across the culture's growth cycle: liquid transitions toward transparency while maintaining homogeneity; no bubbles, precipitates, or color shifts. Perspective: Fixed frontal/slightly angled view, full bottle in frame, table surface visible, no camera movement or cutaways.

Manual:
Experimental Procedure
1. Place a transparent glass bottle containing turbid bacterial culture on a table.
2. Add bactericidal antibiotic solution into the bottle.
3. Mix thoroughly by swirling or inverting.
4. Observe turbidity change over time (time-lapse spanning several hours).
Observation of Experimental Phenomena
Turbidity of the bacterial culture progressively decreases after antibiotic addition and mixing, becoming more transparent across the time-lapse.
Summary of Experimental Principles
A bactericidal antibiotic disrupts bacterial cell walls/membranes, progressively killing and lysing bacteria across the culture's growth cycle; as viable cell density falls over this hours-long process, optical turbidity of the suspension decreases correspondingly, serving as a visual indicator of antimicrobial activity. Bacteriostatic antibiotics, which only halt further growth without killing existing cells, would not produce this turbidity decline.

Prompt Grounding rubric:
level_1: No transparent glass bottle is shown; no turbid bacterial culture is visible inside it; the antibiotic solution is never added; and no mixing motion or any before/after states appear anywhere in the clip.
level_2: A transparent bottle is present, but it holds a clear, non-turbid liquid, or the container is not a bottle (e.g., an open beaker); the antibiotic solution is either never added or appears already inside with no visible entry point; there is no mixing motion and no distinguishable before-and-after state.
level_3: A transparent glass bottle sits on the table holding a visibly turbid, cloudy liquid; a stream of antibiotic solution is shown entering the bottle; the bottle is then swirled or inverted to mix the contents; the clip shows a clear before-addition state and an after-mixing state, even if the transition between them is abrupt.
level_4: A transparent glass bottle holding a turbid bacterial culture sits on the table; a stream of antibiotic solution is shown entering the bottle through its mouth from an identifiable dropper, pipette, or pour spout; the bottle is then swirled or inverted long enough to visibly move the liquid throughout its volume rather than a single brief jostle; the clip shows at least one intermediate visual state between the initial turbid appearance and the final state, in addition to the clear before/after states.
level_5: The bottle stays framed in the same position on the table for the entire clip with no repositioning; the antibiotic stream enters cleanly into the bottle's opening with no spillage onto the table or bottle exterior; the mixing motion is fully contained, with the opening covered or angled so no liquid escapes during swirling or inversion; and the sequence of turbid start, mixing, and a progressively different end state reads as one continuous, uninterrupted time-lapse with no jump cuts or repeated states.

Scientific and Causal Correctness rubric:
level_1: The culture's turbidity is unchanged from before the antibiotic is added to after mixing, staying equally cloudy throughout, consistent with a bacteriostatic antibiotic that halts growth without killing existing cells, but not with the bactericidal, lysis-driven clearing this scenario requires.
level_2: The turbidity changes, but the change is disconnected from the antibiotic: for example, the liquid clears before the antibiotic solution is added, or clears the instant the liquid streams in before any mixing occurs, treating the antibiotic as an instant optical bleach rather than a lytic agent acting on the bacterial population.
level_3: Turbidity is clearly present before the antibiotic is added; after the solution is mixed in, the culture progressively becomes less cloudy across the depicted time-lapse rather than clearing all at once in a single frame; no new colors or precipitates appear that would be inconsistent with simple bacterial clearing.
level_4: Turbid liquid is present before the antibiotic is added and mixed in, and afterward the culture becomes less cloudy in visible stages across the time-lapse rather than jumping straight from turbid to clear in one frame; the liquid stays a single homogeneous phase throughout, with no separated layers or clumped debris settling out, consistent with cells lysing rather than merely settling.
level_5: The final state is markedly and uniformly less turbid than the start, consistent with substantial bactericidal killing of the population; the decline in cloudiness reads as continuous and one-directional, never becoming cloudier again partway through; nothing in the clip suggests an alternative, non-antimicrobial explanation for the clearing, such as visible dilution, filtration, or settling of still-intact cells.

Spatiotemporal Consistency rubric:
level_1: The bottle's position on the table or its size in frame changes abruptly between frames with no connecting motion; the turbid liquid disappears from or appears in the bottle without any pour or mixing action; the swirling or inversion motion cuts directly from stationary to mid-motion with no start of the movement shown; the scene lighting suddenly jumps (e.g., from a bright spotlight to flat ambient light) with no cause; or the bottle visibly warps, bends, or fractures with no force shown acting on it.
level_2: The bottle mostly stays put, but the antibiotic stream or the liquid's cloudiness jumps between visibly different amounts from one moment to the next without a continuous pour or blending motion linking them; the inversion or swirling motion freezes for several frames and then resumes at a different point in the rotation; the bottle's apparent size or distance from the camera shifts unnaturally between shots; or the shadow cast by the bottle shifts position or intensity in a way that doesn't match a fixed light source.
level_3: The bottle remains at a consistent position and distance from the camera on the table throughout; the antibiotic solution's entry into the bottle and the subsequent swirling or inversion proceed as one continuous motion rather than jumping between disconnected states; the turbid liquid's cloudiness changes gradually across the time-lapse rather than snapping between two fixed appearances.
level_4: The bottle stays at a consistent position and distance from the camera on the table throughout, and the liquid's cloudiness responds visibly and proportionately to the mixing motion, such as swirling visibly stirring the liquid rather than the liquid staying static while only the bottle appears to move; the table and bottle keep a fixed spatial relationship with no drift, and no part of the bottle or liquid flickers or briefly duplicates between frames.
level_5: Every stage of the sequence (the antibiotic entering the bottle, the mixing motion, and the progressive change in turbidity) flows as one uninterrupted, physically coherent action with no stutters or skipped states; the bottle's shape, position, and orientation relative to the table stay exactly consistent frame to frame apart from the deliberate swirling or inversion motion itself.