CMMB 343 - Midterm 2 Question and answers rated A+

CMMB 343 - Midterm 2 Question and answers rated A+ CMMB 343 - Midterm 2 What are 4 DIRECT methods of measuring bacterial growth? - correct answer 1. Flow methods: Coulter counter, flow cytometry 2. Microscopic counts: Counting chambers 3. Plate counts 4. MPNs Coulter counter - correct answer electronically scans a volume of fluid as it passes through a tiny pipette. The microbes passing through disrupt the electrical current, which is detected. Flow cytometry - correct answer Similar to coulter counter, except it counts disruptions of a light beam rather than an electrical current. Microscopic counting chamber - correct answer The number of cells visible within a large square are counted under the microscope, and divided by volume. What are the limitations of counting chambers? - correct answer - cannot distinguish between live and dead cells - low precision/accuracy: small cells can be overlooked, and debris can be mistaken for cells - moving cells need to be immobilized - low cell densities are hard to count Plate count - correct answer Capable of measuring VIABLE (living, reproducing) cells. The sample is diluted, and colonies are counted after growth. - ideal dilution is the plate that forms 30 - 300 colonies - two types: spread plate meth