Question

if 0.1 ml of culture was spread on each plate, what is the concentration of transformed cells? the concentration is cells/ml. question 6 answer a. 2.9 cross out b. 27.9 cross out c. 29 cross out d. 45 cross out e. 139.5 crossout f. 145 cross out g. 150 cross out h. 279 cross out i. 290 cross out j. 450 cross out k. 1395 cross out l. 1450 cross out m. 1500 cross out n. 2790 cross out o. 4500 cross out p. 13950 cross out q. 14500 cross out r. 15000 cross out s. more than one of the answers above are correct. cross out t. none of the answers are correct.

Answer 1

The concentration of transformed cells is calculated by multiplying the number of colonies by the dilution factor and the inverse of the volume spread. In this example, the concentration would be 5,000,000 cells/mL. Proper serial dilution and spread plate method are essential for accurate counts.

Step-by-step explanation:

To calculate the concentration of transformed cells in a culture, we use the following information: an average of 50 colonies were counted on plates from a 1:10,000 dilution, and the volume spread on each plate was 0.1 mL. We multiply the number of colonies by the dilution factor and by the inverse of the volume spread. In this case, the concentration of transformed cells would be 50 colonies × 10 (to account for the 0.1 mL volume) × 10,000 (the dilution factor), which equals 5 million cells/mL or 5,000,000 cells/mL.

The count obtained from the 1:1000 dilution was 389, which indicates potential counting inaccuracies due to overcrowded plates, leading to imprecise estimates of cell concentration when colonies number above 300. Through careful serial dilution and the spread plate method, microbiologists can estimate the number of viable cells in a culture. This process includes diluting the culture, spreading samples on agar plates, and counting the resulting colonies to back-calculate the original concentration.