Thiosulfate oxidation by obligately heterotrophic bacteria

Area of Science:

• Microbiology
• Biogeochemistry

Background:

• Thiosulfate is a sulfur compound relevant to microbial metabolism.
• Understanding microbial sulfur transformations is crucial for biogeochemical cycles.

Purpose of the Study:

• To investigate the oxidation of thiosulfate to tetrathionate by various heterotrophic bacteria.
• To determine if thiosulfate oxidation impacts bacterial growth yields.

Main Methods:

• Culturing diverse bacterial species (e.g., Klebsiella aerogenes, Pseudomonas putida, Aeromonas sp.) on different carbon sources.
• Quantitatively analyzing thiosulfate and tetrathionate concentrations during bacterial growth.
• Employing chemostat culture to study enzyme induction and growth yield in Pseudomonas aeruginosa.

Main Results:

• Thiosulfate was stoichiometrically oxidized to tetrathionate by multiple bacterial genera during heterotrophic growth.
• Thiosulfate was not utilized as a sole energy source by any tested organisms.
• Thiosulfate oxidation occurred at different growth stages depending on the bacterial species.
• Pseudomonas aeruginosa growth yield increased in the presence of thiosulfate, suggesting a growth-promoting effect.
• Thiosulfate oxidation in Pseudomonas aeruginosa was inducible.

Conclusions:

• Heterotrophic oxidation of thiosulfate to tetrathionate is a widespread bacterial capability across several genera.
• Thiosulfate oxidation does not necessarily imply its use as an energy source.
• Thiosulfate can potentially stimulate bacterial growth in certain species, though the mechanism remains unclear.