Culturing Bacteria Growth Media Agars… Solid (derived from marine algae) Petri Dish … isolate colonies Slants… to culture (grow) colonies…aerobes Deep tubes… to culture (grow) colonies… Checks for gas requirements Anaerobes…deep Aerobes surface Facultative…mixed Checks for motility

Culturing Bacteria Broth… LB (Luria Bertani) most common Culture to grow large amounts of colonies Amount of growth recorded by turbidity Does not offer differential identification

Differential Growth Media Differential Growth media…helps identify specific colonies Chromogenic growth media uses color for identification Antibiotic selection uses antibiotic rich media to select for transformed bacteria given resistance Ampicillin most common

Kirby-Bauer Disk diffusion test Test is used to determine the sensitivity of different bacteria to antibiotics Zone of inhibition (no growth) describes either the resistance by the bacteria to antibiotics or the sensitivity of the bacteria to the antibiotics

Streak Plating Bacteria Bacterial study requires isolation of a single colony of bacteria Since most objects contain many different species of bacteria a streak plate gives the observer an opportunity to choose a single colony for study Serial streak plates are even more effective

Serial Dilution Method to Reduce Bacteria Often the bacteria are to numerous to effectively separate on a single streak plate. A serial dilution decreases the bacteria count 10X with each dilution Each dilution is plated to get an idea of the amount of bacteria present by counting the CFUs (colony forming units) #of colonies raised x 10 to the power of the # of dilutions Unit is in CFU/ml (21CFU x 105) x 1000ml 100ml 1ml