At normal chilling temperatures for seafood storage, which bacteria predominantly cause spoilage of fish (off-odors, slime, surface softening)?

Introduction:
Cold storage slows microbial growth but selects for psychrotrophic bacteria. This question focuses on identifying the genus most associated with chilled fish spoilage and characteristic sensory defects.

Given Data / Assumptions:

• Chilling refers to near 0–5 °C storage.
• Fish tissues have high moisture and readily oxidizable compounds.
• Psychrotrophs grow at low temperatures and dominate over mesophiles.

Concept / Approach:
Pseudomonas spp. (and related genera like Shewanella) thrive at refrigeration temperatures, forming surface slime layers and releasing volatile compounds (e.g., amines, sulfur notes) that generate typical fishy or sour off-odors. Micrococcus and Bacillus are less dominant under strict chilling in high-moisture, aerobic conditions.

Step-by-Step Solution:
Link chill storage to selection for psychrotrophs. Recall Pseudomonas ecology: aerobic, surface-colonizing, slime-forming. Compare with Micrococcus/Bacillus, which are less competitive on chilled, moist fish. Choose “species of Pseudomonas.”

Verification / Alternative check:
Spoilage trials of iced fish repeatedly isolate Pseudomonas as dominant aerobes causing quality loss.

Why Other Options Are Wrong:

• Micrococcus / Bacillus: May appear but not typically predominant psychrotrophic spoilers of fresh, chilled fish.
• None of these: Incorrect because Pseudomonas is well established.

Common Pitfalls:
Overlooking packaging atmosphere: vacuum or MAP can shift flora, but in aerobic chill storage, Pseudomonas dominates.

Final Answer:
species of Pseudomonas predominate in chilled fish spoilage.