Enter the fungus: a Fusarium species optimised for the production of silver nanoparticles.

This current issue of Memorias do Instituto Oswaldo Cruz presents the results of collaborative work by research groups at the University of Sao Paulo (USP), Federal Univ of Rio de Janeiro (UFRJ) and the National Institute of Metrology, Quality and Technology (INMETRO). These results show how the fungus Fusarium oxysporum might be deployed to generate silver nitrate nanoparticles at higher rates (Ishida et al. 2014). This Fusarium species is an important plant pathogen that is capable of infecting many plant species, including those with agricultural relevance such as tomato, banana, cotton and oil palm (Michielse & Rep, 2009 ). Fusarium oxysporum has been used both as an experimental model for studying plant disease resistance and susceptibility and for the development of biotechnological applications such as the bio-conversion of cellulose to ethanol (Takken & Rep 2010; Ali et al. 2013). Ishida et al. have made significant contributions toward bridging industrial microbiology and nanotechnology, two fields that have a high impact on human activities. The combination of past and current knowledge in these two fields has the potential to expand the domain of 'green chemistry', a concept created by Paul Anastas and John Warner (2008). Using an aqueous extract, Ishida et al. demonstrated that under controlled experimental conditions Fusarium oxysporum is able to generate up to 1 mM silver nitrate in the form of two types of Silver Nanoparticles (SNP): spherical and monodispersal. Traditionally, silver ions have been used as an anti-microbial agent, and before the discovery and industrial production of antibiotics, colloidal silver was the only approved and highly used drug for wound treatment (Mijnendonckx et al. 2013). The exact mechanisms by which silver works in microorganisms remain to be elucidated. It has been suggested that the interactions of silver ions with sulphydryl groups in key enzymes block electron transfer and that downstream intermediate reactions inside the cell lead to microorganism death (Mijnendonckx et al. 2013). Nanotechnology has brought silver back on the stage as an alternative antimicrobial agent, which is especially significant in face of the observed widespread bacterial resistance to antibiotics. The high surface-area-to-volume ratio provides SNP with interesting effects on a variety of pathogenic organisms, including virus, bacteria and multicellular parasites ( Rai et al. 2012; Allahverdiyev et al. 2013; Cheng et al. 2013). However, the disadvantage and challenge for current researchers is that the production of SNP in large quantities, at low cost and under the "12 principles of green chemistry" such that it is affordable for the final consumer is not yet economically viable. In addition, several environmental and toxicity concerns are associated with the widespread use of silver nanoparticles. Currently, the microbial production of SNP is a model only for research laboratories, and further research and development is required make it a viable alternative to conventional production methods. Ishida et al. have advanced one step in this field by demonstrating that Fusarium oxysporum is a good producer of SNP under economically and environmentally viable conditions.

Adeilton Alves Brandão | Publisher Editor


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Allahverdiyev AM1, Abamor ES, Bagirova M, Baydar SY, Ates SC, Kaya F, Kaya C, Rafailovich M. (2013). Investigation of antileishmanial activities of Tio2@Ag nanoparticles on biological properties of L. tropica and L. infantum parasites, in vitro. Exp Parasitol. 135:55-63.

Cheng Y1, Chen X, Song W, Kong Z, Li P, Liu Y. (2013). Contribution of silver ions to the inhibition of infectivity of Schistosoma japonicum cercariae caused by silver nanoparticles. Parasitology, 140:617-25.

Ishida K, Cipriano TF, Rocha GM, Weissmüller G, Gomes F, Miranda K, Rozental S. (2014). Silver nanoparticle production by the fungus Fusarium oxysporum: nanoparticle characterisation and analysis of antifungal activity against pathogenic yeasts. Mem Inst Oswaldo Cruz 109:220-228.

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