Methanotrophs: Environmental Engineers of the Future?

New insight into methanotrophic bacteria that are able to oxidize methane, a potent greenhouse gas, may enable scientists to develop a range of biotechnological applications that provide opportunities for exploiting methane while at the same time protecting the environment. In a paper recently published in Nature, a team of scientists have detailed how methanotrophs use large stores of copper to oxidize methane. The researchers have identified a new family of copper storage proteins, known as Csp, which are present in many bacteria. These proteins are able to store metals in a unique way that has never before been documented, and their presence in a diverse range of bacteria species is causing scientists to question how bacteria utilize copper ions, which can be toxic to cells.

Future Potential

Methane gas is becoming increasingly more available due to natural gas extraction, landfill gas operations and the implementation of methane digestives in agricultural operations. Consequently, the amount of methane leaking out into the atmosphere is also increasing, which is bad for the environment, especially in terms of the implications for climate warming. Methanotrophs consume methane converting it to carbon and energy, and in so doing, serve as the primary biological mechanism for mitigating methane when it is released. Methanotrophic bacteria also offer huge potential for utilizing methane, a renewable source of carbon, in biotechnological applications such as for producing chemicals and renewable energy. Methanotrophic bacteria use an enzyme -- methane monoxygenase -- whose primary cofactor consists of either copper or iron, to metabolize methane. It is therefore important to understand how methanotrophs make use of copper if we wish to make use of the services of these organisms for future applications. Looking at a methanotroph that is able to bind large amounts of copper, the researchers outline and characterize the importance of Csp1 and propose that this protein accumulates copper to facilitate the oxidation of methane. "Methane is such a useful and plentiful commodity but we need more cost effective methods to unlock its potential," explains lead author, Chris Dennison, a professor of Biological Chemistry at Newcastle University. "Using bacteria could be the best option, so a better knowledge of how these bacteria operate is required." "As copper is so important for the oxidation of methane, all potential applications based on this reactivity requires knowing how methanotrophs acquire and store copper," he said. "The discovery of the Csps adds a new dimension to our understanding of this complex process." According to Colin Murrell, a Professor in Environmental Microbiology at the University of East Anglia, and co-author of the paper: "We have known that copper is a vital element for biological methane oxidation for over thirty years and this new information will really help us to formulate new strategies for exploiting these bacteria both in the laboratory and in the environment." Journal Reference: Nicolas Vita, Semeli Platsaki, Arnaud Baslé, Stephen J. Allen, Neil G. Paterson, Andrew T. Crombie, J. Colin Murrell, Kevin J. Waldron, Christopher Dennison. A four-helix bundle stores copper for methane oxidation. Nature, 2015; DOI: 10.1038/nature14854

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