J.C.Murrell@uea.ac.uk

+44 (0)1603 592959 (office) / +44 (0)1603 592239 (lab)

Methane Oxidation In Methanotrophs

Methanotrophs are Gram-negative bacteria that utilize methane, a potent green house gas, as a sole carbon and energy source. These bacteria oxidise methane through a unique enzyme system known as methane monooxygenase (MMO), thus reducing of the amount of methane released to the Earth’s atmosphere. In methanotrophs, there are two types of MMO; a membrane bound particulate enzyme (pMMO) and a soluble cytoplasmic enzyme (sMMO). The expression of both enzymes is significantly affected by the availability of copper. Under high copper-biomass ratio, the biosynthesis of pMMO is switched on while sMMO is upregulated during growth at low copper-to biomass ratio. The exact role of copper in regulation of MMO in Mc. capsulatus is still unclear. We are studying the regulation of methane oxidation in methanotrophs using a combination of post-genomic techniques such as proteomics and transcriptomics and analysing mutants that are defective in copper homeostasis. In collaboration with colleagues in the USA and France we are also studying methanobaction, its biosynthesis and regulation.

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Isoprene Degradation

Isoprene (2-methyl-1,3-butadiene) is a volatile, climate-active gas, produced by all manner of living organisms, including human beings – it is the most abundant volatile organic carbon compound in our bodies! Isoprene is thought to be involved in climate control and in the biogeochemical cycling of carbon – from which our interests stem. We are particularly interested in the pathways and genes involved in isoprene degradation in a variety of model organisms with the hope to develop functional markers for future ecological studies.

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Facultative Methanotrophy at Natural Gas Seeps

One of the most exciting recent developments in the study of biological methane oxidation was the discovery of facultative methanotrophs of the genus Methylocella. Our lab discovered that that the facultative methanotroph Methylocella silvestris can grow on methane as well as other components of natural gas (ethane and propane), thus overturning the dogma that degradation of these gases was carried out by different groups of microbes (Crombie & Murrell 2014). The unique metabolic capability of Methylocella have profound implications for the biological consumption of natural gas in the environment.

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Landfill Methane Biofilters

Methane, a potent greenhouse gas, is generated in landfills by the anaerobic decomposition of deposited organic waste after oxygen has been depleted. Although net release is mitigated in cover soil by methanotrophs (which oxidise methane and use it as a carbon source) landfills remain a significant anthropogenic source of methane

To mitigate the release of landfill gas containing low methane concentrations, Norfolk County Council are trialling a custom-made methane biofilter. Effectively a large bioreactor containing methanotrophs through which landfill gas can be directed and stripped of methane. This biofilter is designed to harness and improve the methane oxidising potential of resident methanotrophic bacteria.

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Marine Methylotrophs

One carbon (C­1) compounds such as methane, methanol and methylamine are used as carbon and energy source by microbes known as methylotrophs. In the marine environment, where these compounds can sometimes be found in surprisingly high concentrations, methylotrophs responsible for metabolising them seem to be ubiquitous. By turning over these compounds in the water column and sediments, methylotrophic organisms therefore play key roles in major biogeochemical cycles. Investigation of the role of methylotrophic bacteria in the marine environment will thus be of significance to answer key questions about the cycling of carbon and nitrogen in marine microbial food webs.

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Movile Cave

Movile Cave is a totally unique environment, situated in the south of Romania. Not only is Movile Cave a fascinating example of a bacterially-driven environment, it is also completely isolated from the outside world – it exists as a sealed “bubble” of life locked below the surface of the Earth. Inspite of being totally sealed and being devoid of light, the Cave is a thriving ecosystem filled with all manner of life, from tiny crustacea to isopods, molluscs and arachnids. On the rest of the planet, ecosystems are supported by primary producers, such as plants or algae, that convert carbon dioxide from the air into living matter that can be eaten by higher organisms – this process is driven by light and is known as photosynthesis. In the dark reaches of Movile Cave, the primary producers are bacteria that convert carbon dioxide into living matter in the form of vast floating “mats” on the surface of the Cave waters. Primary production in the dark is driven by chemical energy obtain by the bacteria from the oxidation of sulfur compounds and ammonia in the Cave waters – a process called chemosynthesis. In addition to this, we believe that a proportion of bacteria in these floating mats form their biomass by consumption of methane found in the geological gases that flow through the Cave – a process known as methanotrophy.

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