PNNL

Abstract

Investigation of microbial mineral respiration remains an experimental challenge. In this issue of Journal of Bacteriology, Rollefson et al. (11) present a foundational study on the functionality of the biofilm matrix in Geobacter sulfurreducens, a model dissimilatory metal respiring bacterium (DMRB). In this study, the investigators identify an extracellular polysaccharide scaffold or network that entraps redox-active proteins, thus positioning these proteins for optimal electron transfer from the membrane-bound respiratory supercomplexes to a mineral phase electron acceptor. The distinguishing feature of this study is the perspective, in that the team examined specifically exopolysaccharide formation and how it enables entrapment and tethering of redox proteins in the vicinity of the cell. Previous studies on Geobacter (10) and Shewanella (4) have focused primarily on the presence and functionality of conductive pili and nanowires, proteinaceous structures that also enable and enhance extracellular electron transfer. Rollefson et al. remind investigators in this field that many microbial systems have redundancy in essential functions, and in the case of DMRB, it is clearly critical that more than one mechanism exists to ensure