Sulfate reduction by a syntrophic propionate-oxidizing bacterium

Area of Science:

• Microbiology
• Environmental Science
• Biochemistry

Background:

• Syntrophic propionate-oxidizing bacteria are crucial in anaerobic environments.
• Methanogens often partner with these bacteria for propionate metabolism.
• Alternative electron acceptors are being explored for microbial growth.

Purpose of the Study:

• To investigate the growth of MPOB (a syntrophic propionate-oxidizing bacterium) in the absence of methanogens.
• To determine the feasibility and efficiency of using sulfate as an electron acceptor for MPOB.
• To compare the growth kinetics of MPOB with other sulfate-reducing bacteria.

Main Methods:

• Culturing MPOB in an anaerobic medium with propionate and sulfate.
• Measuring growth rates (mu) under these conditions.
• Determining growth yields (g dry weight per mol propionate).

Main Results:

• MPOB demonstrated growth by coupling propionate oxidation to sulfate reduction.
• The specific growth rate (mu) was very slow at 0.024 day-1.
• The average growth yield was 1.5 g (dry weight) per mol of propionate.
• MPOB exhibited significantly lower growth rates and yields compared to strict sulfate-reducing bacteria like Desulfobulbus sp.

Conclusions:

• MPOB can utilize sulfate as an electron acceptor in the absence of methanogens, albeit inefficiently.
• The slow growth suggests limitations in the energy metabolism or electron transfer processes.
• Further research is needed to understand the metabolic constraints and optimize the growth of such syntrophic bacteria in alternative electron accepting pathways.