Computerized Counting Microbial Colonies on Petri Dishes: A Do-It-Yourself Approach

The possibility of using a web camera to obtain digital images of microbial colonies on petri dishes and their computer analysis using the ImageJ 1.42 software package (National Institute of Health, United States; https://imagej.net/ij/ ) was shown. Visual counting of colonies on digital images using the ImageJ 1.42 software provides fairly fast and reliable results along with simultaneously documenting the data in a computer. The semi-automatic counting mode makes it possible to configure the software to a visually determined type of colonies. The automatic mode is performed using a special plug-in software and does not require additional configuration. The speed of colony counting in visual mode is about 1 s per colony. Although colony counting in the semi-automatic and automatic modes requires less than 1 s per colony, these approaches may yield results deviating from the actual number of colonies due to the colony size heterogeneity, the presence of conglomerates, as well as optical inhomogeneity of the medium and the presence of microparticles in it, which are not visually accounted for.