Question

1. What is the concentration of bleach that is used to disinfect your work area? Why is it      used to disinfect rather than to sterilize? When do you disinfect your work area? (3             points)
2. Can a pure culture be prepared directly from a mixed-broth or a mixed-slant culture?             Explain. (3 points)
3. As demonstrated in the video, why do you pass the mouth of the tube through the flame? What is the correct angle? (3 points)

5. How do you know that you have used aseptic technique correctly and have achieved a pure culture? (3 points)
6. What are some advantages and disadvantages of the serial dilution agar plate        technique? (3 points)

7. Describe the different cultural characteristics identified when you use agar plates,         agar slants, and nutrient broth. (3 points)

8. Distinguish between the following: (2 points)

1. Disinfectant (1 point)
2. Antiseptic (1 point)

9. What are some advantages of an agar plate over a slant tube? (3 points)
10. Describe how discrete colonies can appear from a mixed culture using the streak- plate subculture process. (4 points)

Answer 1

Que : what are the concentration of bleach that is used to disinfect your work area?

• 5 - 8% of concentrated bleach (active form) is used as disinfectant working area. Which is usually dilute (1:10) with water and then use for disinfect area.
• Because bleach is used as disinfectant working area .it is clean and reduce the contamination present around area and remove some of contamination of organism. Which is most commonly used as decontaminate surface and air
• While sterilization is process to kill microorganism , whether it's harmful or not ( kill spore present on surfaces). Bleach is not used for that . It's done by heat , chemical and radiation.

when do disinfectant your working area

• During streaking or pouring the plates
• As well as spreading your plates from the culture
• Preparation of agar slant for experiment
• Also disinfect some items which is used in experiment like spreader, loops , pipette.

can a pure culture be prepared directly from a mixed broth or mixed slant culture?

• Yes pure culture can be prepared directly from a mixed broth culture.
• In which first dilute the mixture until sperating various types of microbes on agar surface by streaking( streak plate method). After incubation period it will get visble colony formation ( isolation of colonies) by isolation plate
• And then picked off the isolated colony and transferred to new sterile media( selective media) . After incubation all microbes present in new culture will be descendants of the same microbes is known as pure culture.

Que: why do yo pass the mouth of the tube through the flame?

• During the experiment Bunsen burner create flame , when you passed the mouth of the tube through the flame it creates an air flow and hot air rises. Which will reduce air contamination of microbes.

que : what are the advantages and disadvantages of serial dilution.

Advantages:

1. Reduced specific amount of bacteria with every dilution
2. Number of colonies ( isolated) culture from serial dilution sample are counted the estimation of unknown sample concentration.
3. It's very easier and faster preparation of series calibration standard.

Disadvantages:

1. ​​​​​​Needs overnight incubation.
2. It's doesn't sperating bacteria.
3. In which colonies are developed from those organism which are in culture conditions with suitable for growth.

Distinguish between the following

• disinfectant and antiseptic

​​​​​​​Both are the group of drug , that is used for inhibit growth and development to death of organisms present in environments.

• Disinfectant: which is used for cleaning instruments , equipment in laboratory. It's prevent the spread of infection . Bleach is used as disinfectant.
• Antiseptic: it is a chemical substance . Which are used to kill pathogens/ pathogenic microorganisms to prevention of their growth. Turmeric is used as antiseptic.