Growth Patterns in Broth

Different organisms will exhibit varying growth characteristics in broth.  Some organisms will diffuse uniformly throughout the broth; some will sink to the bottom and form a sediment; some will grow in clumps, producing flocculent growth, and some will float on the top of the broth, forming a pellicle.

These growth patterns can be characteristic of an organism and may be used to aid in identifying an unknown organism. However, you must be careful when using growth patterns in broth to identify an organism because the type of broth and the temperature at which the organism is grown can alter the growth patterns. Also, if something happens to shake or otherwise disturb the tube, the growth pattern may be disrupted, and subsequent observation will yield erroneous results.

We do not recommend using growth patterns in broth to identify your unknown. Colonial morphology, cellular morphology, gram specificity, endospore production, and capsule production should provide adequate data for you to solve your morphological unknown.