Table of Contents
International Journal of Evolutionary Biology
Volume 2010, Article ID 602457, 6 pages
http://dx.doi.org/10.4061/2010/602457
Research Article

Elastase Activity in Aspergillus fumigatus Can Arise by Random, Spontaneous Mutations

1Departamento Sanidad Animal, Facultad de Veterinaria, Universidad Complutense de Madrid (UCM), 28040 Madrid, Spain
2Departamento Producción Animal (Genética), Facultad de Veterinaria, Universidad Complutense de Madrid (UCM), 28040 Madrid, Spain
3Departamento Biología Vegetal (Botánica), Facultad de Ciencias, Universidad de Málaga, 29071 Málaga, Spain

Received 27 November 2009; Revised 24 January 2010; Accepted 26 January 2010

Academic Editor: Andrés Moya

Copyright © 2010 Sergio Álvarez-Pérez et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Aspergillus fumigatus Fresenius has the capacity to degrade elastin (the principal protein of the lungs) and it is considered that elastase activity (EA) is among the most important pathogenicity factors of this mold. In particular, there is a strong correlation between EA in A. fumigatus and invasive aspergillosis. However, EA is not universal in this mold, and it is unknown whether the capacity to degrade elastin is the consequence of physiological mechanisms and/or genetic changes (putative adaptive mutations) induced after the exposure to this substrate or, on the contrary, it is due to random spontaneous mutations that occur under nonselective conditions. In order to discriminate between these possibilities, a Luria-Delbrück fluctuation analysis was carried out on an elastase-negative () A. fumigatus strain, using as selective factor a culture medium containing elastin as the sole source of nitrogen. Here we show that the transformation in A. fumigatus appears by rare, random mutations before the exposure of the strain to selective conditions. This work represents the first experimental evidence of pathogenicity factor acquisition in mycelial fungi by preselective mutation.