Microbiology Procedure
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Index >>Bacterial Classification>>Colony Morphology in Bacteria Presumptive Identification

Colony Morphology in Bacteria Presumptive Identification

Bacteria show characteristic type of growth on solid media under appropriate cultureal conditions and the colony morphology can be used in presumptive identification. The colonies can be varying in size and diameter, in outline ( circular, wavy, rhizoid etc.)elevation (flat, raised, convex, etc.) and translucency ( transparent,opaque,translucent). The colour of the colony or the changes that they bring about in their surroundings are also used as diagnostic tools in the tentative identification of the bacteria.

For example, colonies of streptococci on blood agar medium are small, beadlike and have a opalacent grey colour with smooth or slightly rough edges.

Morphological, cultural and colony characteristics provide useful information about the different organisms but these cannot be used as the sole criteria for classification. Further, biochemical, serological and specific tests are often required to be performed before bacteria are clearly identified. Some bacteria produce brilliant pigments, If stable and distinct, the pigmentation is used as an aid in identifying the organism.

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