title: Genetic Identification of a PilT Motor inGeobacter sulfurreducensReveals a Role for Pilus Retraction in Extracellular Electron Transfer.
abstract: The metal-reducing bacteriumGeobacter sulfurreducensrequires the expression of conductive pili to reduce iron oxides and to wire electroactive biofilms, but the role of pilus retraction in these functions has remained elusive. Here we show that of the four PilT proteins encoded in the genome ofG. sulfurreducens, PilT3 powered pilus retraction in planktonic cells of a PilT-deficient strain ofP. aeruginosaand restored the dense mutant biofilms to wild-type levels. Furthermore, PilT3 and PilT4 rescued the twitching motility defect of the PilT-deficient mutant. However, PilT4 was the only paralog whose inactivation inG. sulfurreducenslead to phenotypes associated with the hyperpiliation of non-retractile mutants such as enhanced adhesion and biofilm-forming abilities. In addition, PilT4 was required to reduce iron oxides. Taken together, the results indicate that PilT4 is the motor ATPase ofG. sulfurreducenspili and reveal a previously unrecognized role for pilus retraction in extracellular electron transfer, a strategy that confers onGeobacterspp. an adaptive advantage for metal reduction in the natural environment.
authors: Department of Microbiology and Molecular Genetics, Michigan State University East Lansing, MI, USA.
authors: Allison M
authors: AM
authors: Speers
authors: Department of Microbiology and Molecular Genetics, Michigan State University East Lansing, MI, USA.
authors: Bryan D
authors: BD
authors: Schindler
authors: Department of Microbiology and Molecular Genetics, Michigan State University East Lansing, MI, USA.
authors: Jihwan
authors: J
authors: Hwang
authors: Department of Microbiology and Molecular Genetics, Michigan State University East Lansing, MI, USA.
authors: Aycin
authors: A
authors: Genc
authors: Department of Microbiology and Molecular Genetics, Michigan State University East Lansing, MI, USA.
authors: Gemma
authors: G
authors: Reguera
keywords: electroactive biofilms; metal reduction; pilus nanowires; pilus retraction; type IV pili