Methodology And Determining Criteria For Growth Phase Of Simultaneous Fungal Solid Cultures

Abstract

To develop automation-friendly and highly informative phenotypic methodologies, able to replace with low cost and few procedures’ alterations current fungal solid-media cultures, 5 fungi (3 moulds, 2 yeasts) were cultured onto 3 most common media (SbA, MEA, CzA) at 250 C and 350 C. Growth was estimated daily as a function of diameter increase of the mould mycelia/yeast colonies. The values were plotted by Microsoft XL® commercial software to growth-time charts. Growth is expressed as half-diameter increase, or as surface increase in both raw and logarithmic values. The resulting curves describe the fungal growth so as to establish its kinetics for each isolate in specific medium and temperature conditions and to conclude on possible alterations, in order to achieve, by studying the resulting curves, more accurate description of the growth for more fungi, with better discriminatory and analytical power. The logarithmic values of fungal surface increase were closer to the standard sigmoid curve. Most cultures, though, are already within the deceleration phase of growth after the first 24 hours. Criteria were established to relate the computed, non-sigmoid growth curves to the standard sigmoid curve and to determine its status whenever inconsistencies among the 4 curves plotted for each culture emerged. Using for each isolate in every temperature a single, multi-cell, multi-substrate Petri dish lowers the cost and allows for virtually simultaneous growth on the different substrates. The latter permits fully synchronized graphic charts, making possible the automated and massive processing of isolates, thus leading to the compilation of databases containing reliable descriptive and analytical growth data without the use of complicated prognostic formulas