oxysporum f. sp. melonis. Although the mutants produced all three kinds of asexual spores with normal morphology, they formed markedly fewer microconidia and macroconidia
than the wild type. The mutants appeared to have a defect in the development of the conidiogenesis cells, conidiophores and phialides, required for the formation of microconidia and macroconidia. In contrast, chlamydospore formation was dramatically selleck products promoted in the mutants. The growth rates of the mutants on media were slightly reduced, indicating that FVS1 is also involved in, but not essential for, vegetative growth. We also observed that mutation of FVS1 caused defects in conidial germination and virulence, suggesting that the Fvs1 has pleiotropic functions in F. oxysporum. “
“The pili of Geobacter
sulfurreducens are of interest because of the apparent importance of the type IV pili in extracellular electron transfer. A strain of G. sulfurreducens, designated strain MA, produced many more pili than the previously studied DL-1 strain even though genome resequencing indicated that the MA and DL-1 genome sequences were identical. Filaments that looked similar to type IV pili in transmission electron micrographs were abundant even after the gene encoding PilA, the structural pilin protein, was deleted. The results of proteinase K treatment indicated that the filaments were proteinaceous. The simultaneous deletion of several genes encoding homologues of type II pseudopilins was required before the filaments ICG-001 were significantly depleted. The pilA-deficient MA strain attached to glass as well as the wild-type
old MA did, but strains in which three or four pseudopilin genes were deleted in addition to pilA had impaired attachment capabilities. These results demonstrate that there are several proteins that can yield pilin-like filaments in G. sulfurreducens and that some means other than microscopic observation is required before the composition of filaments can be unambiguously specified. The type IV pili of Geobacter sulfurreducens are of interest because of their proposed role as conduits for extracellular electron transfer to insoluble electron acceptors such as Fe(III) oxides (Reguera et al., 2005) and electrodes (Reguera et al., 2006; Nevin et al., 2009). Fe(III) oxides are the most abundant natural electron acceptors for Geobacter species in a diversity of submerged soils, aquatic sediments, and the subsurface, where these organisms play an important role in the natural cycles of carbon and metals as well as the bioremediation of organic and metal contaminants (Lovley, 1991; Lovley et al., 2004). Extracellular electron transfer to electrodes offers a novel strategy for harvesting electricity from organic wastes and renewable biomass (Lovley, 2006, 2008) as well as environmental restoration (Zhang et al., 2010). The most intensively studied strain of G. sulfurreducens is strain DL-1.
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