Question

In order to count cells, the culture must be duted The technique o serialul precise and quantitative method alle e n al b e performed allow you to determine how many well per miller were the time the were made in overview knowvolume of culturedded to know Volume 0 sterile diluent aliquid that will not harm the cell The liquid in this tube is mixed and known volume of this culture is transferred to another known volume of sterile diluent in another tube. Following mixing this proces repeated until series of cultures has been prepared, each less concentrated than the one previous. Aliquots of each or some of the Serially diluted cultures are septically plated out on semi-solid growth media, the plates are incubated, and colonies are counted. Each colony is assumed to have arisen from a single viable cell (a colony forming unit or CFU) which was immobilized on the agar surface during plating Three equations are used in serial dilutions. Equation is used to determine the individual dilution factor (IDF) of any dilution in the series. This equation also enables you to compare the concentrations of any two tubes next to each other in the series. Equation 1: IDF = Volume transferred Volume transferred + volume of diluent in the blank For example, if you transferred 0.1 iL to a tube that contained 9.9 ml of sterile diluent, the IDF = _01_= 0.1 = 0.01 = 1.0 x 102 0.1 +9.9 10.0 This number tells you that the culture in this tube is 1/100 as concentrated as the culture from which it was made, the previous tube in the series. Equation 2 is used to determine the total dilution factor (TDF). The total dilution factor is used to compare the concentrations of dilution tubes to the original culture tube Equation 2: TDF. the series (DECIDF).(IDF).(IDF), where a, b, c, n refer to different dilutions in For example, if your dilution series consists of 5 tubes, each having an IDF of 0. Ix 10 the TDF = ( x 10 x 10 X1 x 10 X 10 X1 X 10" 1 x 10°. This number tells you that the last tube in the series is 1/100000 as concentrated as the original culture Before going any further, take the time to work out how the IDFs and TDFs were calculated in the figure below using these first two equations. 104

Answer 1

A serial dilution is simply a series of simple dilutions which amplifies the dilution factor quickly
beginning with a small initial quantity of material (i.e., bacltrial culture, a chemical, or fruit-juice, etc.). The source of dilution material for each step comes from the diluted material of the previous.In a serial dilution the total dilution factor at any point is the product of the individual dilution factors in each step up to it.

Final dilution factor (DF) = DF1* DF2 * DF3etc.

IDF = volume transferred/ volume transferred+volume of didiluent

for eg. 0.1/0.1+9.9 = 0.1/10 = 0.01.

Each step 10 dilution or 1:100 10 l 10 10 Mix well Mix well 990 990 Unknown" 990 Total dilution = 102 104 10