Iron biogeobatteries are sustainable electron sources and sinks in the environment

Access to energy resources is critical to global development, and as the climate emergency intensifies it is becoming increasingly evident that we need to develop alternative ways to extract and store energy. An underexploited approach takes advantage of bacteria which have been shuttling electrons between one compound or another for billions of years. Despite the ubiquity of these "mini power stations" in every ecosystem on Earth, we have only just begun to scratch the surface of what they are capable of. In recent years, the ability for different types of iron breathing bacteria to use iron based biogeochemical batteries (biogeobatteries) has emerged. Biogeobatteries are mixed valence iron minerals containing both reduced and oxidized forms of iron that can sustainably act as electron sources or sinks without undergoing physical transformation. This broad definition of a biogeobattery potentially applies to a wide range of mineral phases such as iron oxides, iron-bearing clays, sulphides or green rust. Such minerals are ubiquitous across the planet and could be responsible for a large proportion of energy transfer in subsurface environments. This project will develop a fundamental understanding of how bacteria access biogeobatteries, so that we can learn how to release this potential and perhaps even initiate the advancement of low-cost, low-power energy storage devices for remote locations. This will be achieved by determining the fundamental function of mixed valence iron minerals as iron biogeobatteries and establishing their importance in the environment.

Understanding the function of biogeobatteries in the environment needs access to specialized analytical techniques such as Moessbauer spectroscopy and electron microscopy, coupled to wet chemical dissolution methods. Greater access to these types of instrument is leading to an explosion of experimental data. However, the ability to efficiently analyse this rapidly burgeoning mountain of data, and its subsequent interpretation remains an unresolved issue. To overcome this barrier and spearhead the transformation of data analysis for environmental science, I will create a new platform for analysing Moessbauer spectroscopy data online. This will contrast with the traditional approach by enabling access to continuously updated databases containing both analysed and unanalysed datasets. Through a combination of supervised and unsupervised tools, the complexity of complex environmental samples can be simplified. The long-term aim is to expand into a range of analytical methods which suit the requirements of many different research fields including (bio)geochemistry, geophysics, paleomagnetism, geomicrobiology, and astrobiology amongst countless others. With the system designed to work entirely within a web browser, it can run on any relatively basic computer or smartphone with access to a low bandwidth internet connection. This will open up the accessibility of environmental science to a much broader global community without the need to invest in specialist expertise or costly equipment and software. This platform also offers an opportunity to change how we look at data, minimising the uncertainty and helping to flatten the learning curve for subsequent generations of scientists.

Overall, the work described in this UKRI FLF proposal is highly innovative and multidisciplinary, combining environmental mineralogy, geochemistry and geomicrobiology, with computational methods for data analysis to open a new and exciting branch of environmental science. The successful delivery of this project will have a major impact in terms of deepening our fundamental understanding of microbe mineral interactions, and the use of natural resources to overcome energy storage demands. This work will also have wide reaching implications from how bacteria produce or sequester greenhouse gases, to water quality, and the release of toxic metals and metalloids into aquifers, soils and sediments.