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Nanostructures of noble metals are being investigated for their applications in areas of biology and biotechnology, biological labeling, photothermal, photonics, optoelectronics, catalysis, surface-enhanced Raman scattering (SERS) detection etc. Among the metal nanoparticles, silver nanoparticles are well known for their size dependent properties as well as antibacterial activities. Pulsed laser ablation in liquid (PLAL) is a physical synthesis technique to obtain ultra-pure nanoparticles of metals, semiconductors and ceramics which is a green synthesis compared to other chemical methods. In this chapter, we describe antifungal activities of silver nanoparticles produced by pulsed laser ablation of a high purity silver target in distilled water. The chapter includes details of the synthesis of silver nanocolloids using PLAL and their characterization using various techniques. Antifungal activities of these silver nanocolloids on fungi such as Aspergillus niger and Penicillium spp are explained. These filamentous fungi are responsible for the deterioration of storage life of fruits and vegetables worldwide. The effects of heterogeneous shaped silver nanoparticles produced by PLAL in these two fungal species probed in vitro are discussed. The nanoparticle concentrations from 31.8 to 74.2 mg/L were able to delay mycelium growth and sporulation in both species at the conditions probed. These results open up more biological applications of nanoparticles synthesized by PLAL. [ABSTRACT FROM AUTHOR]

Previously, we demonstrated that when Ustilago maydis (DC) Cda., a phytopathogenic basidiomycete and the causal agent of corn smut, is grown in the vicinity of maize embryogenic calli in a medium supplemented with the herbicide Dicamba, it developed gastroid-like basidiocarps. To elucidate the molecular mechanisms involved in the basidiocarp development by the fungus, we proceeded to analyze the transcriptome of the process, identifying a total of 2002 and 1064 differentially expressed genes at two developmental stages, young and mature basidiocarps, respectively. Function of these genes was analyzed with the use of different databases. MIPS analysis revealed that in the stage of young basidiocarp, among the ca. two thousand differentially expressed genes, there were some previously described for basidiocarp development in other fungal species. Additional elements that operated at this stage included, among others, genes encoding the transcription factors FOXO3, MIG3, PRO1, TEC1, copper and MFS transporters, and cytochromes P450. During mature basidiocarp development, important up-regulated genes included those encoding hydrophobins, laccases, and ferric reductase (FRE/NOX). The demonstration that a mapkk mutant was unable to form basidiocarps, indicated the importance of the MAPK signaling pathway in this developmental process. [ABSTRACT FROM AUTHOR]