Distribution of central carbon pathways: the Entner–Doudoroff (ED) pathway is typically absent from which group of organisms?

Introduction / Context:
The Entner–Doudoroff pathway is an alternative to glycolysis (Embden–Meyerhof–Parnas) for glucose catabolism. Understanding where ED occurs helps in microbial physiology and metabolic engineering.

Given Data / Assumptions:

• ED is common in many Gram-negative bacteria and some archaea.
• Eukaryotes overwhelmingly use the Embden–Meyerhof–Parnas pathway for cytosolic glycolysis.
• Some prokaryotes are aerobic, some anaerobic; ED occurs in both depending on species.

Concept / Approach:
ED pathway enzymes (e.g., 6-phosphogluconate dehydratase, KDPG aldolase) are characteristically prokaryotic. Eukaryotic cytosol lacks the canonical ED route, relying on classic glycolysis.

Step-by-Step Solution:

Verification / Alternative check:
Genome annotations of bacteria such as Pseudomonas and Zymomonas show ED enzymes; standard eukaryotic glycolysis lacks them.

Why Other Options Are Wrong:
Aerobic/anaerobic prokaryotes: ED is present in many of these. Both (a) and (b): Incorrect because ED is not restricted by oxygen preference.

Common Pitfalls:
Assuming ED is rare or specific to anaerobes; it is widespread among diverse bacteria.

Final Answer:
eukaryotes