Question

WHY DO YOU.....

USE CLEAN SLIDES:
REFRIGERATE CULTURES
USE KOVAC’S REAGENT
REFRIGERATE CULTURES
HEAT LOOP
LET LOOP COOL
SIMPLE STAIN

Answer 1

1. We should always use clean glass slides to prevent artefacts caused by dust, fingerprints, smears and scratches. This can be avoided by cleaning the slide with 70% alcohol and dried with lint free tissues. Always touch the edge of the slides.

2. Bacteria can survive for a short period of time at 4°C. Bacterial strains that are used daily or weekly, cultures grown on agar slants or plates can be stored in a refrigerator without any contamination. Cultures should be prepared under sterile conditions and then sealed before storing. Slants cultures are stored in screw capped tubes and cultures in petriplates tubes need to be sealed with Parafilm. Sealing the plates with parafilm slows the agar from drying.  

3. Kovac reagent is a biochemical reagent having follwoing chemicals isoamyl alcohol, para-dimethylaminobenzaldehyde (DMAB), and concentrated hydrochloric acid. It is a diagnostic test to determine the ability of the organism to split indole from the amino acid tryptophan. Indole is one of the end products from bacterial oxidation of the amino acid, tryptophan.

4. The inoculation loop is heated or sterilized with flame until red hot in a microbiology laboratory. This is mainly done to avoid any cross contamination after each use. Similarly the loop is cooled after heated so that the next cells the loop touches are not killed by the hot metal.

5. Simple stain: Simple stain involves or uses only one single stain to determine cell shape, size and arrangements of bacteria. Any basic dye such as methylene blue, safranin, or crystal violet can be used to color the bacterial cells.These stains can easily take hydroxide ion or accept a hydrogen ion, which leaves the stain positively charged. As we know that most of the bacterial cells and cytoplasm is negatively charged, these positively charged stains adhere readily to the cell surface. After staining, bacterial cell morphology can be easily determined.