Distribution of the Entner–Doudoroff (ED) pathway In which groups of organisms is the Entner–Doudoroff pathway found as an alternative catabolic route for glucose?

Introduction / Context:
The Entner–Doudoroff (ED) pathway is an alternative to the Embden–Meyerhof–Parnas (EMP) glycolytic route. It occurs in diverse bacteria and some archaea and is important in microbial physiology, diagnostics, and ecology. Knowing where ED occurs helps predict metabolic capabilities across taxa.

Given Data / Assumptions:

• We are comparing organismal groups: prokaryotes (aerobic/anaerobic) versus eukaryotes.
• Looking for where ED is present as a functional pathway.
• ED is not the dominant sugar catabolism in most eukaryotes.

Concept / Approach:

The ED pathway is widespread among prokaryotes, including aerobic bacteria such as Pseudomonas and anaerobes like Zymomonas. It is rare or absent in typical eukaryotes, which primarily use EMP and the pentose phosphate pathway. Thus, ED spans both aerobic and anaerobic prokaryotes, depending on species and niche.

Step-by-Step Solution:

Verification / Alternative check:

Examples: Pseudomonas putida (aerobic) and Zymomonas mobilis (anaerobic) both use ED prominently, demonstrating presence across oxygen regimes in prokaryotes.

Why Other Options Are Wrong:

• A or B alone: Too narrow; ED is not exclusive to one oxygen condition.
• Aerobic eukaryotes/animal mitochondria: Eukaryotes do not commonly possess a canonical ED pathway.

Common Pitfalls:

• Assuming ED equals fermentation only; it can operate in aerobes as well.

Final Answer:

both (a) and (b)