Use the data below to calculate the colony forming units per mL (CFU/mL) from a sample of bacteria after growing the sample in an incubator for 2 hours. Culture density (CFU/mL) = Time 1 hour Dilution (before plating) 1x 10¹¹ 1x 10-² 1x 10-³ 1x 104 2 hours 1x 10-¹ 1x 10² number of colonies (dilution) x (volume plated, in ml) 1x 10³ 1 x 104 Number of colonies observed Volume spread on plate (replicate plates) 0.1 mL 0.1 mL 0.1 mL 0.1 mL 0.1 mL 0.1 mL 0.1 mL 0.1 mL TNTC 660 101 8 TNTC 220 15 3 TNTC 783 115 7 TNTC 180 26 9 7

A stock solution of a bacterial strain is diluted 1/10000 to a total volume of 500ul. Then, 50ul of the dilution are spread onto a plate. The next day you count 150 colonies. What is the concentration of the stock solution in bacteria/ul?

You have a culture of bacteria with an unknown number of bacteria in it. You have at your disposal 10 1-mL pipettes, 3 dilution bottles that hold up to 100mL of volume, 3 test tubes that hold up to 10mL of volume, a graduated cylinder, an unlimited supply of distilled water. Explain how you would set up a 1: 10,000,000 dilution of your culture.

You are determining the concentration of your culture, and have counted the following on your hemocytometer as shown in Figure below: (note, blue cells have taken up Trypan blue & thus are dead. Red x's are cells that should not be counted because touching one of 2 sides of square). If your cells were diluted 1:2 before counting, what is the concentration of cells in your original culture?

After an antimicrobial drugs test, the following results were obtained from a disk-diffusion test against a bacterium.   Antiboitic A= 6mm Antibiotic B= 18mm Antibiotic C= 11mm Antibiotic D= 19mm which drug should be used to treat an infect caused by this bacterium (assuming everything else is equal about these antibiotics)?

Contrast the overall cell wall compositions of Gram positive and Gram negative bacteria, and go step-by-step in the procedure of the Gram stain. Describe what is occurring during each step within both Gram-positive cells and in Gram-negative cells. Be sure to include the appearance of each cell type at the end of each step.

Compare and contrast bacteriocidal, bacteriostatic and bacteriolytic agents. What are their effects on the optical density (OD) and viable count of a bacterial culture, respectively?

How would you produce a 10^-1 dilution if a 3 mL bacterial sample using the entire 3 mL volume?  suppose your professor handed you a test tube with 2.0 mL of an E. coli broth culture in it and told you to make a 10^-1 dilution of the entire culture. Explain how you would do this. Show your calculations.

The number of bacterial cells in a culture broth is to be determined by a culture technique. Serial dilutions were performed and a 0.1 mL aliquot from each dilution was spread onto Plate Count Agar (PCA). The number of bacterial colony forming units (CFU) after overnight incubation are shown as listed in the table below. What is the number of colony forming units per mL of the culture broth? Choose only the most appropriate plate for your calculation. Give your answer as the number only (do not add text for the units). You may use scientific notation with the format 1.12e+6 (that is, 1.12 x 106 cfu/mL). (Note: Canvas will then display your answer a whole number.) Plate Dilution Plate 1 10 dilution Plate 2 10 dilution Plate 3 107 dilution Plate 4 10 dilution Plate 5 107 dilution Plate 6 100 dilution *Too many to count Number of colony forming units (CFU) TMTC* 382 83 10 2 0

A bacterial culture that has been pretreated with penicillin to inhibit its peptidoglycan synthesis is split and put into solutions of various concentrations. The same is done with a control culture with no prior penicillin exposure. Which condition is likely to demonstrate the biggest difference in outcomes between the control culture and the experimental culture? Placing the cultures into an isotonic solution Placing the cultures into a hypotonic solution Placing the cultures into a hypertonic solution The control and experimental cultures should show you the same results in every condition