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Factors affecting competition between type I and type II methanotrophs in two-organism, continuous-flow reactors
D W Graham1, J A Chaudhary, R S Hanson
1Department of Civil Engineering and Engineering Mechanics, University of Arizona, 85719, Tucson, Arizona, USA.
Microbial Ecology
|November 6, 2013
Summary
Nitrogen limitation favors Type II methanotrophs like Methylosinus trichosporium OB3b over Type I strains by enabling key enzyme expression. This finding suggests a method for selecting specific methanotrophs in bioreactors.
Area of Science:
- Microbial Ecology
- Biotechnology
- Environmental Microbiology
Background:
- Methanotrophs are microorganisms that utilize methane as a carbon and energy source.
- Type I and Type II methanotrophs differ in their metabolic pathways and enzyme expression.
- Type II methanotrophs possess significant cometabolic potential, important for bioremediation.
Purpose of the Study:
- To determine conditions favoring Type II methanotrophs (Methylosinus trichosporium OB3b) over Type I methanotrophs (Methylomonas albus BG8).
- To identify key environmental factors influencing the competitive dynamics between these methanotroph types.
- To explore the potential for selective enrichment of Type II methanotrophs for biotechnological applications.
Main Methods:
- Continuous-flow reactor experiments were conducted using defined concentrations of methane, copper, nitrate, oxygen, and methanol.
- Monitoring of microbial populations (M. trichosporium OB3b and M. albus BG8) under varying nutrient conditions.
- Analysis of enzyme expression (soluble methane monooxygenase and nitrogenase) in response to environmental factors.
Main Results:
- Copper and nitrate limitation strongly favored the dominance of Type II M. trichosporium OB3b.
- A ten-fold increase in M. trichosporium to M. albus ratio was observed upon copper removal.
- Nitrogen limitation led to the decline of M. albus, with M. trichosporium success linked to low dissolved oxygen (<7.5 × 10⁻⁵ M).
- M. albus predominated under methane-limited conditions, especially with co-added methanol.
Conclusions:
- Nitrogen limitation is an effective strategy for selecting Type II methanotrophs, such as M. trichosporium OB3b.
- Environmental factors like copper, nitrate, and oxygen concentrations critically influence methanotroph competition.
- Understanding these dynamics is crucial for optimizing bioreactor performance and harnessing the cometabolic potential of Type II methanotrophs.
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