1. you have performed a serial dilution of a sample with an unknown concentration of microorganisms. you counted 73 cfu on a countable plate inoculated with 0.1 ml of a 10-3 dilution. what was the population density of the original sample per milliliter? 2. compare and contrast the plate count methods for bacterial and viral populations. 3. many of the quantitative methods discussed are popular because they enable the microbiology researcher to selectively count live cells only. why do you think this might be an important or desirable feature in a medical or environmental research situation? provide a scenario in which it might not be important to differentiate between live and dead cells when counting cell numbers.