, 2005). Since those studies, strains of G. sulfurreducens that produce substantially more filaments than strain DL-1 have been identified (Yi et al., 2009; unpublished data), and continued examination of the genome sequence

has revealed additional genes that could potentially encode filament proteins other than PilA. Therefore, the composition of filaments in G. sulfurreducens was investigated further. Geobacter sulfurreducens strain DL-1 (Caccavo et al., 1994) was obtained from our laboratory culture collection. BKM120 Geobacter sulfurreducens strain MA was selected after routine subculturing of strain DL-1 in a medium with acetate as the electron donor and fumarate as the electron acceptor, and exhibited increased this website attachment to glass. Both strains were routinely cultured under anaerobic conditions in NB medium with acetate (10 mM) and fumarate (40 mM) as described previously (Coppi et al., 2001) at 30 °C. For experiments requiring the production of filaments or biofilms, strains were grown in an acetate–fumarate freshwater medium (Coppi et al., 2001) at 25 °C. When required, chloramphenicol was used at a concentration of 15 μg mL−1, spectinomycin at 75 μg mL−1,

and kanamycin at 200 μg mL−1. Genomic DNA extractions from G. sulfurreducens were performed using a MasterPure Complete DNA and RNA purification kit (Epicenter Technologies, selleck chemicals llc Madison, WI). Plasmid purification, PCR product purification, and gel extractions were carried out using QIAprep Spin miniprep kits, QIAquick PCR purification kits,

and QIAquick gel extraction kits (Qiagen Inc., Valencia, CA), respectively. Routine DNA manipulations were performed according to Sambrook et al. (1989). Ligations were carried out using Quick T4 DNA ligase (New England Biolabs, Beverly, MA) or a TOPO TA cloning kit (Invitrogen, Carlsbad, CA). PCR amplifications for cloning purposes contained the Platinum Pfx DNA Polymerase (Invitrogen). The pilA-MAΔ mutant strain was generated by introducing the previously described pilA-specific mutagenic fragment (Reguera et al., 2005) into the MA strain using a previously described protocol (Coppi et al., 2001). The double mutant pilA/oxpG-MAΔ was produced by electroporating an oxpG-specific mutagenic fragment (Mehta et al., 2006) into the pilA-MAΔ mutant. To produce the quadruple mutant, a mutagenic fragment containing a spectinomycin resistance gene flanked by the 501 bp upstream of the pilA gene and by the 595 bp downstream of GSU1497 was introduced into DL-1–MA to generate the mutant pilA/GSU1497-MAΔ. The components of the mutagenic fragment were produced by PCR using the primers specified in Supporting Information, Table S1, restriction digested using enzymes specific to restriction sites introduced by the primers, and ligated to the spectinomycin cassette.