Spotters: Spotter

C) Spotter

12. Antibiotic sensitivity plate set up by Kirby Bauer technique

• Kirby Bauer technique is used to determine the susceptibility of the organism to various antimicrobial agents.

• Standard suspensions of rapidly gowing test bacterium is inoculated on the surface of muller hinton agar plates.

• Antibiotic discs are pressed on the surface of the seeded plates.

• The zone of inhibition or the zone of growth determines the degree of susceptibility of the organism towards antibiotic.

13. Sugar fermentation tube showing acid and gas production

• Carbohydrate broth with bromocresol purple as indicator is used for testing the ability of pure bacterial culture to ferment a specific sugar like lactose, xylose, mannitol and other sugars.

• Acid production is indicated by colour change of the indicator from purple to yellow

• Gas production is indicated by an air bubble in the durham’s tube.

• Escherichia coli ferments lactose producing acid and gas.

In the above image Test tube C was innoculated with cell suspension and incubated at 37 C for 24 hours and after innoculatior the purple color of broth was changed to yellow color with gas bubble formation in durham's tube.

14. Agarose gel electrophoresis apparatus.

• Electrophoresis refers to the movement of charged molecules in an electric field.

• The negatively charged molecules move towards the positive electrodwhile the positively charged molecules migrate towards the negative electrode.

• Gel electrophoresis is a routinely used anytical technique for the separation and purification of specific DNA fragments.

• As the DNA is negatively charged, DNA fragments move through the gel towards the positive electrode. The rate of migration of DNA is dependent on the size and shape.

13. Spoiled food

• Spoilage is a process in which food deteriorates such that its quality of edibility is reduced.

• Food poisoning may result on eating contaminated or spoiled food.

• Foods spoil due to attacks from enzymes, oxidation and microorganisms.

• These include bacteria, mold, yeast, moisture, temperature and chemical reaction.