Two isoforms of Geobacter sulfurreducens PilA have distinct roles in pilus biogenesis, cytochrome localization, extracellular electron transfer, and biofilm formation.

TitleTwo isoforms of Geobacter sulfurreducens PilA have distinct roles in pilus biogenesis, cytochrome localization, extracellular electron transfer, and biofilm formation.
Publication TypeJournal Article
Year of Publication2012
AuthorsRichter LV, Sandler SJ, Weis RM
JournalJ Bacteriol
Volume194
Issue10
Pagination2551-63
Date Published2012 May
ISSN1098-5530
KeywordsAmino Acid Sequence, Bacterial Adhesion, Base Sequence, Biofilms, Cytochromes, Electron Transport, Fimbriae Proteins, Fimbriae, Bacterial, Gene Expression Regulation, Bacterial, Geobacter, Molecular Sequence Data, Protein Isoforms, Protein Transport, Reverse Transcriptase Polymerase Chain Reaction, Surface Properties
Abstract

Type IV pili of Geobacter sulfurreducens are composed of PilA monomers and are essential for long-range extracellular electron transfer to insoluble Fe(III) oxides and graphite anodes. A previous analysis of pilA expression indicated that transcription was initiated at two positions, with two predicted ribosome-binding sites and translation start codons, potentially producing two PilA preprotein isoforms. The present study supports the existence of two functional translation start codons for pilA and identifies two isoforms (short and long) of the PilA preprotein. The short PilA isoform is found predominantly in an intracellular fraction. It seems to stabilize the long isoform and to influence the secretion of several outer-surface c-type cytochromes. The long PilA isoform is required for secretion of PilA to the outer cell surface, a process that requires coexpression of pilA with nine downstream genes. The long isoform was determined to be essential for biofilm formation on certain surfaces, for optimum current production in microbial fuel cells, and for growth on insoluble Fe(III) oxides.

DOI10.1128/JB.06366-11
Alternate JournalJ. Bacteriol.
PubMed ID22408162