Growth rates vary greatly depending on the strain and culturing conditions. For slow growing cultures, growth may not be readily apparent to the naked eye and may require examination by microscope or spectrophotometer to determine if cells are dividing. Cultures often go through a "lag" phase when first inoculated into new medium or when introduced to new growth conditions.

Some potential parameters to troubleshoot if you are unable to stimulate growth in your culture: 

  • media composition
  • light intensity
  • temperature
  • the presence of residual detergent or bleach on glassware.