Iron management and production of electricity by microorganisms

Abstract

The increasing dependency on fossil fuels has driven researchers to seek for alternative energy sources. Renewable energy sources such as sunlight, wind, or water are the most common. However, since the 1990s, other sources for energy production have been studied. The use of microorganisms such as bacteria or archaea to produce energy is currently in great progress. These present several advantages even when compared with other renewable energy sources. Besides the energy production, they are also involved in bioremediation such as the removal of heavy metal contaminants from soils or wastewaters. Several research groups have demonstrated that these organisms are able to interact with electrodes via heme and non-heme iron proteins. Therefore, the role of iron as well as iron metabolism in these species must be of enormous relevance. Recently, the influence of cellular iron regulation by Fur in the Geobacter sulfurreducens growth and ability to produce energy was demonstrated. In this review, we aim to briefly describe the most relevant proteins involved in the iron metabolism of bacteria and archaea and relate them and their biological function with the ability of selected organisms to produce energy.

Spatially Resolved Chemical Analysis of Geobacter sulfurreducens Cell Surface

“…The size of the FeCPs is highly reproducible (average diameter 5.6 nm; Figure A,C; Figure S4), similar to cytochromes, FeS proteins, or Fe-transporters (Table S3). , Compared to the cell surface, FeCP are enriched in Cu (Figure D) which is specific for Fe oxidases . The density of these particles on the bacterial surface is relatively high (they cover about 2% of cell surface), and they are more or less equally distributed over the cell (Figure A).…”

“…The large particles have an irregular shape and size, and their origin is not clear. Based on their shapes, they might be either associates of the small FeCP or the initial steps of the formation of big Fe aggregates detected before on G. sulfurreducens cell surfaces. , It was demonstrated that planktonic G. sulfurreducens cells are able to acquire Fe from the surrounding medium and use it for extracellular respiration. , This effect is temperature dependent . To test the role of temperature in the formation of FeCPs, we performed HAADF and EDXS analyses of the cells cultivated at 25 °C.…”

“…Bacterial pili (type-IV filaments) are very interesting structures that are responsible for cell attachment to inorganic surfaces, , to each other, and other organisms. , Planktonic G. sulfurreducens clusters might use pili for keeping the cells together and also for acquiring Fe and transferring it to the cell surface. , Some data suggest that the pili of G. sulfurreducens are conductive and responsible for ET from the cells to the electrode (extracellular respiration) . The presence of Fe in pili might substantially improve their conductivity. , To test the possibility of Fe attachment to G. sulfurreducens pili, we analyzed Fe content in the filaments by EDXS.…”

“…1,39 Compared to the cell surface, FeCP are enriched in Cu (Figure 1D) which is specific for Fe oxidases. 40 The density of these particles on the bacterial surface is relatively high (they cover about 2% of cell surface), and they are more or less equally distributed over the cell (Figure 2 A). Similar density on the G. sulf urreducens cell surface was observed by immunolabeling for some ET proteins like OmcS and OmcZ cytochromes.…”

Sustained effect of zero-valent iron nanoparticles under semi-continuous anaerobic digestion of sewage sludge: Evolution of nanoparticles and microbial community dynamics

“…It is an essential redox element (between Fe 2+ and Fe 3+ forms) fundamental for biological processes that functions as a versatile cofactor for numerous proteins in biological processes. It plays a fundamental role in biological processes such as DNA replication and repair among others, but also as an electron donor and acceptor in many microorganisms such as Archae and Bacteria (Folgosa et al, 2015). Although iron is one of the most abundant elements on earth, its bioavailability is not as extensive as it would be expected, since at neutral pH its solubility is 0.1 M and 10 −8 M, for Fe 2+ and Fe 3+ , respectively.…”