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.

    112/152 (page 100)
    coli, the number of indol-producing bacteria is a measure of the amount of pollution in a sample of water. 1. Take out i c.c. from No. 5 dilution (see Exercise 77). v v I v 55 N O 4 „ „ v 11 i 5? » E o. 3 11 v 2. Pour each into a broth-culture (See Exercise 14) and incubate at 3 7 0 C. 3. Test for Indol after 1—2 days. (See Exerc. 4 3 and 44.) 1 c.c. from No. 5 dilution contains 1 -- c.c. of sample i v „ hi o. 4 v r> No. *2 0 1.00U 1 To An effluent which gives a negative result with 1 o' 0 c.c. should be “passed” as a non-potable water, for it denotes the absence of B. coli and its allies in sufficient numbers to cause any danger to the public health. Exercise 82. Examination of a Sewage or Sewage-effluent for Bac. enteritidis sporogenes (Klein). Crude sewage contains on the average 100 spores of this organism per c.c. In our dilutions therefore (see Exercise 77). 1 c.c. No. 1 flask ( N c.c. Sewage per c.c.) contains 10 spores of this I „ No. 2 „ I 100 ” V V V organism 1 spore „ „ 10 » No. 3 „ ( 1 v 1.000 ” V V „) V I v v v IOO v No. 4 v w 0 ^ 0 0 V V I V V V We have here, therefore, a means of estimating the amount of pollution in any sample of badly polluted water by comparing its number of Bac. enter, sporog. with the number of this organism found in crude sewage. Klein's Method. 1. Boil 4 tubes each containing about 15 c.c. of milk for d hour. This is done to expel the oxygen from the milk. 2. Cool rapidly by immersing in large beaker containing cold water.