File:6. Културелни карактеристики на Escherichia coli.ogv

English: Cultural characteristics of Escherichia coli:

1. From the liquid culture with Escherichia coli, inoculate one test tube with the following media: nutrient broth, MacConkey broth, ALPV.

2. From the liquid culture with Escherichia coli, inoculate one test tube with slant agar with the following media: nutrient agar, MacConkey agar and Simmons citrate agar, so that an inoculum is taken with a sterile loop and pulled through the middle of the slant agar.

3. From the liquid culture with Escherichia coli, inoculate one tube of deep agar with nutrient agar, so that the inoculum is taken with a sterile needle, the tube is rotated to an almost vertical position and a sting is made in the middle of the agar column.

4. From the liquid culture with Escherichia coli, inoculate the plates with the following media: nutrient agar, MacConkey agar, Endo agar, EMB agar, mFC agar and starch agar.

All plates and tubes are incubated at 37 ° C for 24 hours.

RESULT:

1. The following characteristics are observed on the previously inoculated test tubes with liquid medium:

- Nutrient broth - turbidity of the medium

- MacConkey broth - discoloration to yellow because lactose is fermented to acidic products, which lower the pH

- ALPV - discoloration of the substrate to pink and production of gas (CO2 or H2) which is detected by the accumulated gas in the Durham tube

2. The following characteristics are observed on the previously inoculated test tubes with slant agar:

- Nutrient agar - dense, white colonies along the slope of the agar in the test tube

- MacConkey agar - yellow color change because lactose is fermented to acidic products, which lower the pH

- Simmons-citrate agar - no growth of the bacterium Escherichia coli was observed, because there is no change in the color of the medium, i.e. this bacterium does not use the citrates that are in the substrate.

3. The following characteristics are observed on the previously inoculated test tube with deep agar:

- Nutrient agar - growth of bacteria on the deep agar column in the test tube

4. The following characteristics are observed on the previously inoculated plates with different media:

- Nutrient agar - large, white colonies on the surface of the agar plate

- MacConkey agar - yellow color change because lactose is fermented to acidic products, which lower the pH

- Endo agar - large green colonies with a green fluorescent glow

- EMV agar - E.coli which strongly ferments lactose and gives acidic products that cause precipitation of the color on the surface of the colony, is metallic green in color

- mFC agar - E. coli which is a coliform bacterium, grows on this medium which is selective for coliforms in the form of dense, large, colorless colonies

- Starch agar - After incubation, the grown colonies are flooded with Lugol's solution. The substrate is blue, because the starch with iodine gives a blue complexion. The color of the zones depends on the degree of hydrolysis of the starch. The areas around α-amylase-containing bacterial colonies are either colorless or reddish brown.

Planned and performed by Sofija Kostandinovska, Department of Biology, FNSM, Ss. Cyril and Methodius University, Skopje, Macedonia.