Metabolic Flux Analysis Reveals Entner-Doudoroff Pathway Dominance in Heterotrophic Deep-Sea Bacterial Isolates

Area of Science:

• Microbiology
• Metabolic Engineering
• Oceanography

Background:

• Deep-sea microorganisms possess unique metabolic adaptations to extreme environments.
• Intracellular carbon flux pathways in these organisms are not well understood.

Purpose of the Study:

• To investigate and compare central carbon metabolic fluxes in four deep-sea bacterial strains.
• To identify conserved and unique metabolic strategies employed by these bacteria.

Main Methods:

• Utilized 13C metabolic flux analysis with isotopologues to trace carbon flow.
• Analyzed glucose degradation pathways, pentose phosphate pathway activity, and anaplerotic strategies.
• Conducted oxidative stress assays to assess hydrogen peroxide tolerance.

Main Results:

• All four strains predominantly utilized the Entner-Doudoroff pathway (66.7%-94.0% glycolytic flux).
• Shewanella piezotolerans WP3 showed significant pentose phosphate pathway flux, indicating high precursor and redox demands.
• Diverse anaplerotic strategies (phosphoenolpyruvate or pyruvate carboxylation) were observed for tricarboxylic acid cycle replenishment.
• A correlation between intracellular energy status and hydrogen peroxide tolerance was found.

Conclusions:

• The Entner-Doudoroff pathway is a conserved and dominant glycolytic route in deep-sea heterotrophs.
• Deep-sea bacteria exhibit varied metabolic strategies for carbon utilization and survival in high-pressure, carbon-limited environments.
• Metabolic flux analysis provides key insights into the adaptability of deep-sea microbial life.