BMY3201-1 BASIC MICROBIOLOGY TECHNIQUES
WHAT HAVE I LEARN?
We enter Part 4 of experiment, which is the cultivation of microorganisms: nutritional and physical requirements, and Enumeration of Microbial Populations. This week we have to do two experiment.
Experiment 12: Nutritional requirements: Media for the Routine Cultivation of Bacteria. We add Escherichia coli, Alcaligenes faecalis and Streptococcus mitis inorganic synthetic broth, glucose salts broth, nutrient broth and yeast extract broth. The next day, we use the spectrophotometer to measure the turbidity at 600nm wavelength. We can see that the E. coli have the most numbers in the yeast extract broth compare to other medium. However, A. faecalis and S. mitis is more in nutrient broth compare to other medium.
Experiment 13: Use of differential, Selective, and Enriched Media
There are many special- purpose media is used in isolation of bacterial types. The selective media including Phenylethyl alcohol agar, crystal violet agar and 7.5% sodiul chloride agar used to isolate specific groups of bacteria by inhibiting the growth of one type of bacteria while permitting of another. Differential and also selective media act as to distinguish morphologically related groups of bacteria. Media included Mannitol salt agar, MacConkey agar and Eosin- methylene blue agar.Last one is the enriched media, which is the blood agar. This is used to cultivate fastidious microorganisms which have special nutritional needs. We can see the hemolytic properties of streptococcus, which classify into gamma hemolysis, alpha hemolysis and beta hemolysis. Beta hemolysis is complete destruction of hemoglobin which causes clear zone to be seen surrounding colonies. Hemolysis is produced by streptomycin O and streptomycin S. It's really interesting because there is many different colour change of colonies formed on the bacteria and also surrounding the bacteria. For example, the E. coli appear to be blue black, green sheen on eosin- methylene blue agar after incubation.
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| This is spectrophotometer |
Cuvette which used to contain culture before put into spectrophotometer
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| Staphylococcus shows clear yellow zone surrounding the growth |
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