Preparation of Culture Media:  Because of time constraints, you will not be asked to prepare any of the culture media used in this course.  A lab technician does this for you.  However, it is important that you understand what procedures are involved to prepare them.  Since nutrient broth and nutrient agar are used routinely in many of our laboratory exercises, the preparation of these complex media will be covered.     

	Preparation of Nutrient Broth Tubes
	Preparation of Nutrient Agar Deep Tubes, Slant Tubes, and Plates

Maintenance of Stock Cultures:   Each semester our laboratory purchases stock cultures from a reputable supplier.  These cultures are used throughout the semester for preparing the working cultures you use in lab.  To promote the continued viability of stock cultures, our lab technician periodically subcultures each species to fresh culture medium.  Most of our stock cultures are renewed this way every 3-4 weeks.  Despite this preventative routine, it is worth mentioning that stock culture viability may not always be maintained indefinitely.  Each transfer increases the chance of mutation, possibly leading to undesirable changes in the organism's genotypic and phenotypic characteristics.  Consequently, stock cultures that begin to exhibit meager growth may become unsuitable to prepare working cultures from.

Incubation of Cultures:  To promote rapid multiplication after inoculation, tube or plate cultures are placed in an incubator.  Since the microbes you work with are mesophilic (optimum growth temperatures ranging between 20-40ºC), our lab utilizes three separate incubators set at 25ºC, 30ºC, and 37ºC, respectively.  Each culture is placed in the incubator corresponding best to the microbe's known optimum growth temperature.  The length of incubation varies by species.  Most bacteria require 24-48 hours of incubation, whereas fungal species may need 3-6 days to exhibit adequate amounts of growth.