Aseptic Technique & Culturing Microbes

Questions
A. What is the difference between a bactericidal and bacteriostatic agent? What is the difference between sterilization and disinfection?

Control of growth refers to the prevention of growth of microorganisms. This control is affected in two basic ways: by killing microorganisms or by inhibiting the growth of microorganisms. Control of growth usually involves the use of physical or chemical agents which either kill or prevent the growth of microorganisms. Agents that kill cells are called cidal agents; agents that inhibit the growth of cells without killing them …show more content…
Two types of media will be used to grow the microbial specimens: nutrient medium and MRS medium. Though both media are available in liquid broth and solidified agar form, this experiment will use the liquid broth. Nutrient medium is the standard growth medium used for culturing most microbes. It consists of heat-stable digestive products of proteins (called peptones) and beef extract. These ingredients provide amino acids, minerals, and other nutrients used by a wide variety of bacteria for growth.
The MRS culture medium contains polysorbate, acetate, magnesium, and manganese which are known as a rich nutrient base and act as special growth factors for lactobacilli. The MRS medium will be used to culture Lactobacillus acidophilus. L. acidophilus will not grow sufficiently in nutrient media. I. Describe your microscopic observations of the cultures.

The following observations were made in viewing the L. acidophilus and S. epidermidis under the microscope. L. acidophilus’ shape consisted of rods with rounded ends and appeared to grow as singular organisms. S. epidermidis appeared spherically shaped and occured in grape-like clusters. arranged in grape-like clusters and formed white, raised, colonies.

J. Define the following terms:
Psychrophiles or cryophiles (adj. cryophilic) are extremophilic organisms that are capable of growth and reproduction in cold temperatures, ranging from −15°C to +10°C.