Metabolic and energetic control of Pseudomonas mendocina growth during transitions from aerobic to oxygen-limited conditions in chemostat cultures.

Abstract

Several metabolic fluxes were analyzed during gradual transitions from aerobic to oxygen-limited conditions in chemostat cultures of Pseudomonas mendocina growing in synthetic medium at a dilution rate of 0.25 h-1. P. mendocina growth was glucose limited at high oxygen partial pressures (70 and 20% pO2) and exhibited an oxidative type of metabolism characterized by respiratory quotient (RQ) values of 1.0. A similar RQ value was obtained at low pO2 (2%), and detectable levels of acetic, formic, and lactic acids were determined in the extracellular medium. RQs of 0.9 +/- 0.12 were found at 70% pO2 for growth rates ranging from 0.025 to 0.5 h-1. At high pO2, the control coefficients of oxygen on catabolic fluxes were 0.19 and 0.22 for O2 uptake and CO2 production, respectively. At low pO2 (2%), the catabolic and anabolic fluxes were highly controlled by oxygen. P. mendocina showed a mixed-type fermentative metabolism when nitrogen was flushed into chemostat cultures. Ethanol and acetic, lactic, and formic acids were excreted and represented 7.5% of the total carbon recovered. Approximately 50% of the carbon was found as uronic acids in the extracellular medium. Physiological studies were performed under microaerophilic conditions (nitrogen flushing) in continuous cultures for a wide range of growth rates (0.03 to 0.5 h-1). A cell population, able to exhibit a near-maximum theoretical yield of ATP (YmaxATP = 25 g/mol) with a number of ATP molecules formed during the transfer of an electron towards oxygen along the respiration chain (P/O ratio) of 3, appears to have adapted to microaerophilic conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

• Authors: N Verdoni, M A Aon, J M Lebeault
• Journal: Applied and environmental microbiology (Appl Environ Microbiol) Vol. 58 Issue 9 Pg. 3150-6 (Sep 1992) ISSN: 0099-2240 [Print] United States
• PMID: 1444429 (Publication Type: Journal Article)

Chemical References

• Culture Media
• Glucose
• Oxygen

Topics

• Aerobiosis
• Anaerobiosis
• Culture Media
• Ecology
• Energy Metabolism
• Glucose (metabolism)
• Oxygen (metabolism, pharmacology)
• Oxygen Consumption (drug effects)
• Pseudomonas (drug effects, growth & development, metabolism)