Practical bacteriology for chemical students / by David Ellis.

  • David Ellis
Date:
1923
Catalogue details

Licence: In copyright

Credit: Practical bacteriology for chemical students / by David Ellis. Source: Wellcome Collection.

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    7. Examine a loopful from No. 3 tube under the micro- scope, using the etched cover slip and this time examine the water systematically by bringing each square in turn under examination. [The object of dividing the cover- slip into squares is to enable the whole drop which is under the coverslip to be systematically searched.] 8. If more than one cell is found in this loopful still another dilution must be made until some certainty is reached that a loopful taken from the fluid contains either no yeasts or only one. When this is the case, set 12—24 tubes* containing beer- wort in a row and inoculate each with a loopful from the fluid diluted as described The chances are then very great that when development takes place in any one of these, all the organisms in that particular tube have been derived from a single organism. The culture is therefore pure. Exercise q8. Pure Culture of Yeast (Lindner Method). 1. Carry on the same procedure as in the preceding exer- cise until it is found that there is approximately one Yeast to one drop of the fluid. 2. With a sterile fine-bored pipette withdraw a portion of the fluid diluted to this extent and place droplets on the floor of a sterile Petri-dish. It is probable each drop will contain only one Yeast cell. 3. Each drop that contains a cell will develop into a colony after incubation (200 C.). 4. Touch a drop in which growth has taken place with a platinum needle and with this infect a tube containing a sterile nutrient medium. The probabilities are very great that the resulting growth will be a pure culture. Exercise 99. Moist chamber Experiment. 1. Melt a small quantity of beer-wort gelatine and mix with a drop or two of a fluid containing healthy Yeast * Hansen’s flasks for culturing Yeasts will be found very convenient for this purpose (see Fig. 9e). Ellis’ Practical Bacteriology.