上气通大学 Shanghai Jiao Tong University 2、直接计数法 血球计数板动画 1)常规方法：显微镜下对微生物数量（总数）进行直接计数 Figure 6.19 Direct Grid with 25 large squares microscopic count of bacteria with a Petroff-Hausser cell Cover glass counter.The average number of cells within a large square Slide multiplied by a factor of 1,250,000 gives the number of bacteria per milliliter. Direct microscopic counts are useful for certain applications Bacterial suspension is added here but have a disadvantage of re- and fills the shallow well over the quiring rather high microbial squares by capillary action. populations for them to be countable. Bacterial suspension Microscopic count:All cells in several large squares are Cover glass counted,and the numbers are averaged.The large square Slide shown here has 14 bacterial cells Location of squares 4 The volume of fluid over the 2 Cross section of a cell counter. large square is 1/1,250,000 The depth under the cover glass is known. of a milliliter.If it contains 14 and the area of the squares is known. cells,as shown here,then there so the volume of the bacterial suspension are 14 times 1.250,000 over the squares can be calculated(depth x area) (17,500,000)cells in a milliliter 陈峰，上海交通大学生命学院微生物学Shanghai Jiao Tong University 陈峰，上海交通大学生命学院微生物学 2、直接计数法 1）常规方法：显微镜下对微生物数量(总数)进行直接计数 血球计数板动画