Domain: Natural Science — Microbiology
Target concept: The solution turns yellow, no gas is produced.

Video generation prompt: Glucose fermentation tube (with phenol red indicator, inverted Durham tube) inoculated with lactic acid bacteria, cultured at 37°C, and photographed after cultivation.

Evaluation guide:
(i) Target concept: Acid production without gas evolution in homofermentative lactic acid bacteria fermentation.
Minimum mechanism: Glucose must be metabolized exclusively to lactic acid (no mixed-acid or butanediol pathways); phenol red must be present and functional as pH indicator; Durham tube must be correctly inverted to trap gas *if produced*; incubation must allow sufficient time for metabolic acid accumulation but not degradation.
(ii)Storyline: Frame 1: Sterile loop contacts medium surface → Frame 2: Loop withdraws, Durham tube fully visible inside tube → Frame 3: Static incubation cue (e.g., incubator label or thermal blur fade) → Frame 4: Final static shot of tube showing yellow medium and empty inverted Durham tube; all frames share fixed frontal viewpoint, consistent lighting, and no occlusion; causal chain requires inoculation → acid accumulation → color change → no gas → empty Durham tube; visibility mandates full view of medium color and entire Durham tube interior.

Manual:
Experimental Procedure
1. Inoculate glucose-phenol red broth in fermentation tube using sterile loop.
2. Insert inverted Durham tube before capping.
3. Incubate at 37°C for 24–48 h.
Observation of Experimental Phenomena
Medium turns uniformly yellow; no gas bubble appears in inverted Durham tube.
Summary of Experimental Principles
Lactic acid bacteria ferment glucose to lactic acid → lowers pH → phenol red changes from red/pink to yellow; no gas (CO₂/H₂) is produced.

Prompt Grounding rubric:
level_1: No fermentation tube is visible; no phenol red medium color is shown; no inverted Durham tube appears inside any tube; no inoculation loop or lactic acid bacteria culture context is depicted; no 37°C/incubation cue (incubator background, label, or thermal cue) is present.
level_2: A single tube appears, but at least one required element is wrong or missing: e.g., the medium is clear/colorless instead of phenol red pink-red, the Durham tube is absent or sits right-side-up instead of inverted, the inoculation loop never touches the medium, or the scene reads as room-temperature with no 37°C/incubator cue.
level_3: The glucose-phenol red broth tube with an inverted Durham tube fully submerged inside it is shown; an inoculation loop contacts the medium surface at some point; a post-incubation static shot of the capped tube appears; the tube, Durham insert, and medium color are all visible together within one fixed frontal view.
level_4: All score 3 conditions hold AND the tube is unambiguously identifiable as the phenol red-glucose broth (medium tint and Durham tube shape are both clearly rendered, not implied only by a label); the loop-contact step reads as one discrete inoculation action that finishes before the incubation cue begins; the final shot contains only the capped tube itself, with no extra glassware, reagent bottles, or bench clutter in frame.
level_5: All score 4 conditions hold AND the tube sits centered, front-facing, and unobstructed with no glare across the glass hiding the Durham tube or medium color; the loop is fully withdrawn and out of frame before the incubation/final shot begins; there is no visible 'before-inoculation' comparison frame; the final shot holds a static, centered composition with no camera pan, zoom, or added motion.

Scientific and Causal Correctness rubric:
level_1: The broth is not yellow (it stays red/pink, or shifts to an implausible hue such as purple or orange); or a distinct gas bubble/void sits trapped at the closed end of the Durham tube; or no color change from the original red is shown at any point.
level_2: The broth has turned yellow, but the Durham tube is missing from view, OR a bubble-like void appears at the Durham tube's closed end that cannot be clearly ruled out as trapped gas (e.g., an ambiguous bright patch or debris blocking the tip).
level_3: The broth is uniformly yellow throughout the visible medium, the inverted Durham tube is fully visible inside the broth, and no gas bubble or void appears at the closed end of the Durham tube in the same shot as the yellow color.
level_4: All score 3 conditions hold AND the yellow color fills only the liquid broth (not smeared on the tube wall or cap) AND no gas bubble, froth, or trapped air pocket is visible anywhere along the length of the inverted Durham tube, from its open mouth to its closed tip.
level_5: All score 4 conditions hold AND the yellow shade matches phenol red's acid (yellow) endpoint rather than an intermediate orange, AND the Durham tube keeps its correct inverted orientation (open end down) with its closed end staying completely gas-free for the entire time the tube is shown on screen: no bubble ever appears, even briefly.

Spatiotemporal Consistency rubric:
level_1: The fermentation tube's position or size changes abruptly between shots with no camera motion connecting them; the background switches from bright daylight to a dark incubator setting with no transition; the Durham tube's orientation flips from inverted to upright with no intermediate motion; or the tube's glass appears to crack, bend, or reshape between frames.
level_2: The Durham tube blinks out of view for a frame and then reappears; the inoculation loop's position jumps between frames without a visible sweep; the broth surface jitters or ripples with no nearby cause (no loop or hand movement); or the background brightness changes noticeably from one frame to the next with no stated cause (e.g., incubator door, fade cue).
level_3: The fermentation tube stays in the same place and orientation across the whole sequence; the Durham tube remains nested at the same depth and angle inside it; the broth surface is still except during the loop-contact moment; the tube's shadow on the bench keeps the same direction and size across frames.
level_4: All score 3 conditions hold AND any hand/loop motion during inoculation is smooth and comes to a full stop before the incubation cue begins; the tube and its background stay in the same relative position with no sliding or drifting; the tube's cap, Durham tube, and broth level look continuous frame to frame with no jump in height or angle.
level_5: All score 4 conditions hold AND there is no duplicated or skipped frame, no ghosting trail behind the loop or tube, and no unexplained blur on the tube or Durham tube while the rest of the shot stays sharp; the tube keeps the same scale, angle, and depth relationship to the bench throughout, from the inoculation step to the final static shot.