Rapid throughput analysis of filamentous fungal growth using turbidimetric measurements with the Bioscreen C: a tool for screening antifungal compounds

Abstract

A rapid method for screening antifungal compounds and performing ecophysiological studies with filamentous fungi has been developed by the use of specific semi-solid media and spectrophotometric/turbidimetric measurements using the Bioscreen C with 2×100 microtitre well plates. The medium composition and preparation, inoculum size, medium volumes, and incubation parameters for measuring initial germination and growth dynamics have been optimised. These have been applied to assess the effectiveness of 18 concentrations of propyl propane thiosulfinate (PTS) against Aspergillus flavus in YES medium under different environmental regimes. Minimum inhibitory concentrations (MIC), and non-inhibitory concentration (NIC) values, and a newly developed MIC(50), have been calculated for the efficacy of these concentrations of PTS under four different environmental conditions (0.995 and 0.95 water activity (a(w)); 20 and 25°C) over 7d periods with automated measurements every 20 min. Data were modelled using the Lambert-Pearson Model, a mathematical modelling approach previously used for bacterial inhibition. Results have been compared with traditional growth rate data and Lethal Dose(50) (LD(50)) values. This approach could have major implications for rapid screening assays for growth and secondary metabolite production by filamentous organisms and has major advantages in terms of time reduction, culture medium volumes required, measurement and the ability to integrate and model key parameters for comparing efficacy.