Objective: Mucor circinelloides is a saprophytic fungus classified under Mucorales order of subphylum Mucoromycotina and showing dimorphism-dependence on oxygen, with medical, industrial, biotechnological and agricultural significance. The aim of this study is to show the transformation of M. circinelloides yeast and mould forms and to reveal the virulence characteristics of these two forms in an in vivo Galleria mellonella larvae model.

Methods: M. circinelloides was incubated under anaerobic and aerobic conditions to show its mould to yeast and yeast to mould transformation. Yeast and mould forms were examined under the microscope with direct uncoloured, lactophenol cotton blue and methylene blue preparations. Randomly selected 70 larvae were used as in vivo larvae model. Infected larvae were incubated under 30°C and the number of survived larvae was documented; thus the virulence of the yeast and mould forms were compared.

Results: Mould colony was isolated after 96 hours of incubation at 37°C on Sabouraud dextrose agar plates. Subcultured mould colony transformed into the yeast form after 96 hours of incubation at 25°C in a desiccator box. Survival rates of larvae infected by yeast and mould forms were found to be similar.

Conclusion: We concluded that there was no significant difference between virulence of M. circinelloides yeast and mould forms in G. mellonella larvae model.