Nanowire-mediated iron acquisition in bacteria

Jern og mangan er essensielle elementer for bakterier. Men i vår oksygenholdige atmosfære er disse elementer utilgjengelige for bakterier i mange naturlige miljøer, fordi disse er kompleksert med oksygen. Elektron donasjon til disse oksidene kan konvertere jern til en slags som kan brukes av bakterier. I dette prosjektet har vi allerede vist at bakteriell pili er viktig for å få tilgang til jernoksider og manganoksider. Vi er i ferd med å identifisere molekære komponenter som formidler elektrondonasjon til ekstracellulære elektronacceptorer og karakteriserer elektrondonasjonsfunksjoner. For dette har vi evaluert mutanter og konstruert et mutasjonsbibliotek som vi analyserer på fenotyper ved bruk av jern og mangan. I tillegg utfører vi karakterisering av elektrondonasjonsfunksjonene til forskjellige mutenter ved hjelp av elektrodesystemer. Vi undersøker og kvantifiserer også hvilke kilder av jern kan brukes av marine cyanobakterier. For dette har vi implementert et definert jernmedium for dyrking av cyanobakterier.

The project "Nanowire-mediated iron acquisition in bacteria" established a link between the ability of cyanobacteria to access iron that is contained in oxidized iron minerals. This link has been established through data obtained from physiological, electron microscopy, and gene expression data that uses wild-type and pilin deletion mutants. Genetic deletion of pili results in changes in the photosynthetic electron transport chain, as well as reductive nitrogen metabolism and extracellular carbohydrates.Furthermore, the main pilin in the model cyanobacterium Synechococcus sp. PCC 7002 has been identified as well as the operon for siderophore biosynthesis.

This project addresses the utilisation of a resource that is fundamental to life: Iron There is strong evidence that bacterial pili have a function in donating electrons to iron oxides. However, this electron disposal has so far only been interpreted as to enable respiration of soil bacteria in anaerobic conditions. In contrast, we have collected data that indicates that pili and a cytochrome are crucial for iron acquisition in the cyanobacterium Synechocystis sp. PCC 6803. We hypothesise that pili are meditating electron donation to iron oxides, thereby converting insoluble ferric iron (Fe3+) into soluble ferrous iron (Fe2+), which can readily been taken up by bacteria. In this application we propose to determine the molecular structures and mechanisms that enable iron acquisition in bacteria, using the cyanobacterium Synechocystis sp. PCC 6803 as a model. As iron is an essential, albeit often limiting element for all bacteria, the extracellular conversion of Fe3+ into soluble Fe2+ has enormous implications, ranging from marine primary productivity to human disease. This proposal also aims to gain fundamental structural insight into the pili-cell interface through the implementation of cutting-edge imaging approaches. In addition to addressing the role of pili in iron acquisition, our proposal may also provide crucial understanding required to employ photosynthetic bacteria in the construction of truly renewable photovoltaic devices.