. Advanced biology. Biology; Physiology; Reproduction. OCCURRENCE OF BACTERIA 397 In preparing agar slants, the test tubes must be plugged with sterile cotton and sterilized thoroughly. Then, the plug is re- moved, the sterile agar quickly poured in, and the plug put back in the mouth of the test tube. The test tubes are usually set obliquely for the agar to cool, so that, when firm, the surface of the media is slanting. Hence the term agar slant. This method gives more surface for the growth of bacteria. In order to introduce bacteria for cultivation into a Petri dish, the dish is uncovered a
. Advanced biology. Biology; Physiology; Reproduction. OCCURRENCE OF BACTERIA 397 In preparing agar slants, the test tubes must be plugged with sterile cotton and sterilized thoroughly. Then, the plug is re- moved, the sterile agar quickly poured in, and the plug put back in the mouth of the test tube. The test tubes are usually set obliquely for the agar to cool, so that, when firm, the surface of the media is slanting. Hence the term agar slant. This method gives more surface for the growth of bacteria. In order to introduce bacteria for cultivation into a Petri dish, the dish is uncovered and exposed to the air. After the expo- sure, the dish is kept closed. Bacteria may also be introduced with water, food, dust, or other foreign material. In introducing bacteria into the agar slant, the cotton plug is removed carefully so as not to get bacteria on it. The agar slant is then streaked or stuck with a needle infected with bacteria. Occurrence of bacteria. Bacteria are so extremely minute that they float in the air with the particles of dust. It is almost im- possible to find any air that does not contain them. Since this. One way of growing colonies of bacteria is on 5n agar slant preparation. The surface of the agar is streaked with the material containing the bacteria. The long slant gives considerable surface on which growth may take place. '^:^ is the case, it is quite impossible for any material exposed to the air, for even a short time, to escape contamination from Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Wheat, Frank Merrill; Fitzpatrick, Elizabeth T. New York ; Boston [etc. ] : American Book Company
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