Halobacterium produces distinctive pink/red carotenoid pigments (predominantly bacterioruberin, a 50-carbon carotenoid, alongside the retinal-containing integral membrane protein bacteriorhodopsin).
Flavobacterium produces bright yellow-to-orange non-water-soluble carotenoid pigments.
Micrococcus (e.g., M. luteus, M. roseus) produces yellow, orange, or red carotenoids.
Leuconostoc (lactic acid bacteria) forms small, grayish-white, non-pigmented colonies on culture media.

Statement 4 is NOT true: Spherical bacterial cells (cocci) have the smallest surface-area-to-volume ratio, making vegetative cocci (such as Staphylococcus aureus and Enterococcus faecalis) generally more heat-resistant than non-sporeforming vegetative rod-shaped bacteria (bacilli / rods), not less resistant. Statements 1, 2, and 3 are all biologically accurate.

Microbial pathways of fish spoilage and nucleotide catabolism:

• Streptococcus cremoris (Lactococcus lactis subsp. cremoris) is a dairy lactic starter culture.
• Shewanella putrefaciens is a dominant psychrotrophic marine spoilage bacterium. It degrades post-mortem nucleotides (ATP $\to$ ADP $\to$ AMP $\to$ IMP $\to$ inosine $\to$ hypoxanthine), leading to progressive accumulation of hypoxanthine which imparts a pronounced bitter off-flavor, while also reducing TMAO to fishy TMA.
• Paraburkholderia fungorum is an environmental soil bacterium.
• While S. frigidimarina is cold-adapted, S. putrefaciens is the primary recognized spoilage agent responsible for intense hypoxanthine off-flavor.