Identification of an extracellular polysaccharide network essential for cytochrome anchoring and biofilm formation in Geobacter sulfurreducens.

Transposon insertions in Geobacter sulfurreducens GSU1501, part of an ATP-dependent exporter within an operon of polysaccharide biosynthesis genes, were previously shown to eliminate insoluble Fe(III) reduction and use of an electrode as an electron acceptor. Replacement of GSU1501 with a kanamycin resistance cassette produced a similarly defective mutant, which could be partially complemented by expression of GSU1500 to GSU1505 in trans. The Δ1501 mutant demonstrated limited cell-cell agglutination, enhanced attachment to negatively charged surfaces, and poor attachment to positively charged poly-d-lysine- or Fe(III)-coated surfaces.

Identification of genes involved in biofilm formation and respiration via mini-Himar transposon mutagenesis of Geobacter sulfurreducens.

Electron transfer from cells to metals and electrodes by the Fe(III)-reducing anaerobe Geobacter sulfurreducens requires proper expression of redox proteins and attachment mechanisms to interface bacteria with surfaces and neighboring cells. We hypothesized that transposon mutagenesis would complement targeted knockout studies in Geobacter spp. and identify novel genes involved in this process.

Microbial biofilm voltammetry: direct electrochemical characterization of catalytic electrode-attached biofilms.

While electrochemical characterization of enzymes immobilized on electrodes has become common, there is still a need for reliable quantitative methods for study of electron transfer between living cells and conductive surfaces. This work describes growth of thin (<20 microm) Geobacter sulfurreducens biofilms on polished glassy carbon electrodes, using stirred three-electrode anaerobic bioreactors controlled by potentiostats and nondestructive voltammetry techniques for characterization of viable biofilms. Routine in vivo analysis of electron transfer between bacterial cells and electrodes was performed, providing insight into the main redox-active species participating in electron transfer to electrodes.

Herpesvirus-like DNA sequences in non-Kaposi's sarcoma skin lesions of transplant patients.

Herpesvirus-like DNA sequences (KSHV) have been reported to be associated with various forms of Kaposi's sarcoma (KS). To determine if KSHV was associated with other proliferative skin lesions from non-AIDS immunocompromised patients, 33 skin lesions (basal cell carcinomas, squamous cell carcinomas, actinic keratoses, verruca vulgaris, atypical squamous proliferations, and seborrhoeic keratosis) from 4 organ-transplant patients receiving immunosuppressive therapy were tested for KSHV by PCR. KSHV sequences were detected in 82% of these skin lesions.