Bacterial and fungal colonies growing on solid agar media show greatly diverse characteristics. Characteristics of colonies of a specific microbial species are markedly stable. The characteristic morphology of a microbial colony usually points to and tentatively suggests a particular type of microorganism upon examination of gross morphology. Therefore, any identification scheme for a microbial isolate should start with a thorough description of the characteristics of colonies. Tentative identification of type of organism (bacterial or fungal) and suspected genera or species, based on colonial morphology, may help early exclusion of a wide range of other microbial types thus reducing the number of potential candidates in the subsequent identification steps. Furthermore, colonial morphology is important in recognizing mutational changes in the population which take place upon repeated subculturing of microbial strains. Mutant colonies usually show alterations in colonial properties such as surface, texture, or color, which can be easily differentiated from the wild type.
A description of colony characteristics usually includes the shape (form), margin, elevation, optical properties, texture, and pigmentation of the colonies.
This original Flash animation illustrates various colonial aspects in simple and colorful presentation. It is intended as an illustrative teaching tool in the microbiology laboratory.