Mind the Gap

Oeiras, 07.11.12

Some bacteria are able to produce electrical currents, a trait which is being exploited for electricity production in a technology known as microbial fuel cells. But how these bacteria manage to link intracellular metabolism with extracellular electron delivery has been one of the last standing mysteries of their metabolic routes. Research conducted at the Inorganic Biochemistry and NMR lab and at the Protein Modelling lab in the context of a project funded by the MIT-Portugal program revealed the co-existence of two independent pathways that enable electrons to cross the gap between the bacteria inner and outer membranes. This research was accepted for publication in the Biochemical Journal.

Respiration in electrochemically active bacteria is peculiar in the sense that the production of ATP, the molecular currency for energy in all living organisms, takes place in the inner membrane but the terminal electron acceptor of the respiratory chain is found outside the cells. While there were several proposals on how electrons could cross that space, no experimental test had been provided so far. Now, researchers show that in Gram negative bacteria two molecular routes reach across the periplasmic gap to deliver electrons to the cell surface. In both routes, electrons travel via transient protein-protein interactions but, even though proteins share the same cell compartment, the two routes do not exchange electrons. This result reveals exquisite discrimination in the recognition of protein partners and the molecular bases for this discrimination were identified.

Original Article

Biochem. J. (2012) Immediate Publication, doi:10.1042/BJ20121467

Mind the gap: cytochrome interactions reveal electron pathways across the periplasm of Shewanella oneidensis MR-1

Bruno M Fonseca, Catarina M Paquete, Sónia E Neto, Isabel  Pacheco, Claudio M Soares and Ricardo O Louro