In vitro inhibitory effect of ozone gas on zoospores and hyphae of Pythium insidiosum

Efeito inibitório in vitro do gás ozônio sobre zoósporos e hifas de Pythium insidiosum

ABSTRACT:

This study evaluated the inhibitory effect of ozone gas (O₃) on the mycelia and zoospores of Pythium insidiosum and verified the morphological changes it caused on the hyphae. The effects of O₃ were evaluated on the mycelia (n = 21) and zoospores (n = 10) of P. insidiosum. O₃ was bubbled into vials with sterile distilled water and mycelium or induction medium and zoospores. After 15 minutes, aliquots of mycelia and zoospores were grown on yeast agar at 37 °C/96 hours. Ozonated flasks were incubated at 37 ºC/72 hours; and every 24 hours, aliquots were subcultured at 37 ºC/96 hours. Transmission (TEM) and scanning (SEM) electron microscopy of O₃-exposed hyphae were performed. The results revealed that O₃ inhibited microorganism growth in all ozonated suspensions. Conversely, in control suspensions, P. insidiosum growth occurred within 24 hours of incubation. In the SEM, the treated hyphae presented cavitations and cell wall continuity loss; in the TEM, the organelles and cytoplasmic membrane disappeared, and the cell wall was retracted. We demonstrated, for the first time, that O₃ causes irreversible damage on P. insidiosum hyphae and prove in vitro oomicidal action on zoospores and hyphae.

Key words:
pythiosis; oomycete; oomicidal; ozone therapy; O₃