Automated image analysis to observe pellet morphology in liquid cultures of filamentous fungi such as the basidiomycete Coprinopsis cinerea

In this study, an image analysis system for fungal pellets was developed using the commercial software system analySIS^® and the protocol was evaluated in morphological studies of pellet formation in submerged cultures of the basidiomycete Coprinopsis cinerea. Pellets were analysed on large scale (60 to 130 pellets per image, 225 to 400 pellets per culture). Morphologies of pellets were characterised by the parameters grey value, pellet area, convexity, shape factor, sphericity and pellet diameter. Threshold values were defined for all parameters for object filtering. By application of the parameter filter, aggregated hyphal fragments present in larger amounts particularly in cultures grown at higher temperature (37°C) could be clearly distinguished in image analysis from compact pellets. At a lower growth temperature (25°C), there was little background of loose hyphal material, fungal pellets were regularly shaped and the pellets remained constant in shape and size over a longer cultivation period.