Carbon Source Influence on Extracellular pH Changes along Bacterial Cell-Growth

Area of Science:

• Microbiology
• Environmental Science
• Biochemistry

Background:

• Bacterial growth is influenced by environmental factors, including pH.
• Understanding pH dynamics is crucial for predicting bacterial behavior in various settings.

Purpose of the Study:

• To investigate the impact of initial pH on bacterial growth and pH evolution.
• To identify the role of different media and carbon sources in pH changes.
• To correlate observed pH changes with metabolic activity using genome-scale models.

Main Methods:

• Culturing three bacterial strains (Escherichia coli, Pseudomonas putida, Pseudomonas pseudoalcaligenes) in different media (LB, MM).
• Monitoring pH changes over time during bacterial growth under aerobic heterotrophic conditions.
• Utilizing genome-scale metabolic models to predict and explain observed pH shifts.

Main Results:

• Bacterial strains exhibited specific pH convergence points in LB media.
• Minimal Medium (MM) generally maintained more stable pH, with glucose causing slight acidification.
• Escherichia coli growth was arrested below pH 6, while other carbon sources led to either acidification or alkalinization.

Conclusions:

• Bacterial growth and pH changes are significantly determined by the culture medium's composition, especially the carbon source.
• Genome-scale metabolic models accurately predict pH changes, revealing underlying metabolic mechanisms.
• This research aids in predicting bacterial pH dynamics, interspecies interactions, and fitness in environments.