Stopping the air from turning blue

Concerns are being raised that some biofuel crops may increase the production of a climate changing gas known as isoprene – now research suggests microbes in the soil could combat the effects of this gas and improve air quality. We hear from the scientists behind a project examining the role of these microbial in mopping up… The Blue Ridge Mountains get their name from a blue haze arising from the release of a gas called isoprene that is produced by trees. In the natural environment isoprene is an important precursor of many components of living cells and it can help protect plants from heat stress and light damage enabling them to cope better at higher temperatures. However, isoprene can also react with certain chemicals in the atmosphere to change the levels of ozone and other gases, which in turn has an impact on our climate. An area of concern is that isoprene production may well increase as crops such as willow and poplar, which are big isoprene producers, are grown more widely to make biofuels. This concern is driven by the knowledge that isoprene-producing oil palms grown widely in tropical rainforests have already been shown to increase levels of damaging ozone, so it is important to understand what impact increased isoprene levels will have on air quality and how these impacts can be mitigated. Isoprene (2-methyl-1,3-butadiene) is a climate-active gas and is one of the most abundant volatile organic carbon compounds released into the air. In the upper atmosphere, isoprene can react with oxygen in the presence of oxides of nitrogen to produce ozone (O₃), which has obvious environmental consequences. Additionally it is also thought that by adding small particles to the air, isoprene contributes to the formation of cloud condensation nuclei that develop into clouds. Isoprene has a potent role in climate control and also in the biogeochemical cycling of carbon, however these pathways are unknown. Isoprene is produced by a variety of living organisms in both terrestrial and aquatic environments, mostly by plants but also fungi, bacteria and animals. Although the exact role is not known, in plants more isoprene is produced in hotter environments. There are microbes that use isoprene and perform a role in ‘mopping’ it up from the atmosphere. Through our knowledge of methane-consuming bacteria, we have been able to develop investigative tools, which can be used to inform land use management decisions.  In this project we aim to do the same for isoprene and as this is such an abundant gas, it could have a significant impact on air quality. The Earth and Life Systems Alliance (ELSA), is a Norwich Research Park initiative that aims to better understand the effects of climate change on biodiversity and the major biogeochemical cycles. The Principal Investigator of this project, Colin Murrell, who is the Director of ELSA and Professor in the School of Environmental Sciences at University of East Anglia says: “The role of micro-organisms is poorly understood so my team within ELSA, together with Dr Terry McGenity of the University of Essex, are working on a Natural Environment Research Council (NERC) funded project to investigate the distribution, diversity and activity of isoprene degrading bacteria. “We have discovered that isoprene is metabolised in a variety of bacteria by a multicomponent enzyme called isoprene monooxygenase. This is similar to an enzyme (methane monooxygenase) that oxidises another climate active gas, methane. “We are particularly interested in the pathways and genes involved in isoprene degradation. So we are now looking at how the function of this isoprene monooxygenase enzyme is regulated in bacteria in response to the availability of isoprene, using a variety of molecular and biochemical techniques. “We will be culturing known isoprene-degrading microbes, focusing on those that live naturally in soil and on leaf surfaces. Then, using powerful molecular biology-based techniques, we will determine the DNA sequences of the genes involved in isoprene degradation.” By studying metabolic activity in a variety of model organisms, it will be possible to develop functional markers for future ecological studies and use these to identify species capable of removing isoprene gas from the air. Additionally, it is known from work on methane that the monooxygenase enzyme has unusual catalytic properties; for example it can breakdown propane. So by studying isoprene, there is potential to discover new bio-catalysts with novel properties. Researchers at the University of Essex bring particular expertise in soil science. Alongside this study, a PhD student will measure isoprene consumption in forest soils, and also for the first time, on leaves from various tree species, comparing isoprene emitters with non-emitters. This will bring a new understanding of where the active microbes occur in soils, the surface of plant leaves and trees and what contribution they make in mitigating the release of isoprene into the atmosphere. Dr McGenity says: “We will be able to test whether adding permutations of isoprene-degrading microbes to leaf surfaces enhances isoprene consumption. By measuring the microbes' ability to survive or grow on the leaves, we will obtain insights into whether this is a potential strategy for reducing isoprene flux to the atmosphere. All the data emanating from this project will be valuable for management of bioenergy crops, in relation to greenhouse gas emissions.” Isoprene production is increased as temperatures rise. By furthering our knowledge of its natural cycle and degradation pathway, we might also be able to predict how climate change may affect the production of this poorly studied climate-active gas. In addition the research aims to determine potential management strategies. For example, to see if increasing the density of bioactive microbes when cultivating known isoprene emitters will impact release of the gas. Work from the team may also help inform the selection of trees for urban environments so that isoprene emitters are avoided. Further information Earth & Life Systems Alliance www.elsa.ac.uk Murrell Lab: www.jcmurrell.co.uk About Norwich Research Park www.norwichresearchpark.com