(一)以数量变化对微生物生长情况进行测定 1、培养平板计数法 1 ml 1 ml 1 ml 1 ml Origina 9 ml broth inoculum in each tube Dilution 1:10 1:100 1:1000 1:10.000 1:100,000 1 ml 1 ml 1 ml 1 ml Plating 1:10 1:100 1:1000 1:10,000 1:100.000 Calculation: Number of colonies on plate x reciprocal of dilution of sample- number of bacteria/ml For example, if 32 colonies were on a plate of 1/1ooo dilution, then the count is 32 x 10,000=320,000/ml in sample. Figure 6.15 Plate counts and serial dilutions. In serial dilutions, the original inoculum diluted in a series of dilution tubes. In our example, each succeeding dilution tube will have only one-tenth the number of microbial cells as the preceding tube. Then samples of the dilution are used to inoculate Petri plates, on which colonies grow and can be counted. This count is then used to estimate the number of bacteria in the original sample. The most frequently used method of measuring bacterial populations is the plate count.（一）以数量变化对微生物生长情况进行测定 1、培养平板计数法