Extracellular Electron Transfer Proteins Contribute to Reduction of Ferric Minerals by Geobacter Biofilms
Extracellular electron transfer between dissimilatory iron-reducing microorganisms and iron bearing minerals largely drives the biogeochemical cycle of Fe, one of the most abundant elements on Earth. Fe oxides exist in variable mineral forms. Because of this environmental diversity, microbes have evolved various EET pathways composed of numerous c-type cytochromes. To adapt environmental cues, such as electron acceptors with different redox potentials, DIRMs alter its EET system by upregulating the expression of specific c-Cyt genes. How microbes regulate their EET network to adapt environmental stimuli remains an important question. Recent studies, showed that dinucleotide second messengers, i.e., cyclic di-GMP and cyclic AMP-GMP, play important roles in regulating EET of DIRMs, such as Geobacter spp. But previous studies conducted in the systems with the reduction of electrode or a limited range of Fe oxides, so a comprehensive understanding of the regulatory role of c-di-GMP and c-di-GAMP in EET between microbes and ferric minerals is still lacking.