The number of colonies that develop is the number of viable microbial cell in the volume of liquid that was filtered. This technique is great for concentrating a sample, ex. Growth Factors - Microbes can exist in a great many environments because they are small, easily dispersed, need only small quantities of nutrients, are diverse in their nutritional requirements. A. Physical Factors 1. The use of salt as a preservative in curing meats and the use of sugar in making jellies is based on the fact that a hypertonic environment kills or inhibits microbial growth.
Some bacteria have enzyme systems that can repair some mutations.
B. Oxygen Requirements 1. Clostridium tetani 2. E. coli , Staphylococcus 4. The loop is flamed and a few bacteria are picked up from the region already deposited and streaked onto a new region. Fewer and fewer bacteria are deposited as the streaking continues, and the loop is flamed after each streaking.