Resistance of airborne fungal propagules to ultraviolet irradiation: Laboratory study

Abstract

The influence of ultraviolet (UV) radiation on fungi Aspergillus niger Tiegh. isolate OG168, Paecilomyces puntonii (Vuill.) Nann. isolate OG68, and Penicillium expansum Link isolate PO88 was studied under laboratory conditions. A test system was developed for this study. An aerosol chamber provided a dust-free space of 1.5 m 3 . The source of ultraviolet rays was an UV lamp (DPT 220, 240-320 nm, 15 W). Fungal propagules were injected into the UV exposed chamber space from an external bioaerosol generator. Aerosols from the aerosol chamber after irradiation to UV were sampled into an impinger AGI-30 and measured with the optical aerosol spectrometer LAS-15M (Institute of Physics, Lithuania). The changes in fungi survival caused by exposure to UV radiation were evaluated by determining their relative recovery. The laboratory study indicated that the fungal propagules responded to UV radiation distinctively. P. puntonii propagules were injured without possibility to repair. On the contrary, P. expansum propagules repaired after a long enough exposure to UV radiation, but this ability was limited. The stressed A. niger propagules recovered after the 80 min exposure to UV radiation and the relative recovery reached a plateau. The mutagenic effects of UV light on tested fungi have shown that frequent occurrence of different morphological mutants was detected after the 30 min exposure of conidia. The mean geometrical diameter of fungal propagules exposed to UV irradiation in the aerosol chamber was in the range of 2.5 to 2.8 µm.

Ultraviolet radiation as a controlling and mutating agent of environmental fungi

“…The doses necessary to kill B50 percent of conidia varied between 1,080 and 1,800 mJ/cm 2 /sec depending on the fungus species and B77-88.5 percent of conidia were killed after exposing to 2,160 mJ/cm 2 . The variations in susceptibility may be attributed to cell size, structure of cell wall or membrane, pigmentation and the existence of a repair system (Ulevicius et al, 2008). The efficacy of UVC irradiation is a function of UV intensity, exposure time, lamp placement, air movement and methodology used (Ko et al, 2000;Lin and Li, 2002).…”

Effect of the oscillating magnetic field on airborne fungal

“…This shows that the OMF applied affects the pigmentation of the colonies, regardless of nutritional status of the fungus, which is showing a similar behavior when applied ionizing radiation on C. neoformans (Dadachova et al 2007) and simulated sunlight radiation of 320 nm on P. puntonii (Ulevičius et al 2008), higher than 400 nm on Pythium sp. (Hughes et al 2003) or higher than 750 nm on Alternaria solani (Stevenson 1988).…”

“…This might indicate an adaptation of the genus Aspergillus to any radiation, because it was observed that the stressed A. niger propagules were recovered after the 80 min exposure to UV radiation and the relative recovery respect with P. puntonii and P. expansum (Ulevičius et al 2008). That was similar to the slight resistance of A. parasiticus on irradiated chestnuts with 0.25-3.0 kGy of gamma radiation (Cabral et al 2011).…”

“…Research studies of (Ulevičius et al 2008) demonstrated that the fungal propagules of Aspergillus niger, Paecilomyces puntonii and Penicillium expansum responded to UV radiation distinctively. The propagules of P. puntonii were injured without possibility to repair.…”

Penicillium expansum (Blue Mold)

“…Gamma radiation had no effect on the decay of 'Anjou' pear fruit naturally infected with P. expansum and B. cinerea, however, a reduction in decay was observed in naturally infected 'Bosc' pear fruits treated with 0.90 kGy. Different morphological mutations were detected in the conidia of P. expansum isolate PO88 that were exposed to UV radiation for 30 min and some of the conidia repaired after the exposure (Ulevičius et al, 2008). Foaad et al (2002) demonstrated that a dose of gamma radiation at 1.0-3.0 kGy inhibited the growth of P. expansum and patulin production.…”