Mycological Laboratory Procedures

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Questions and Answers

What is the typical pore size for sterilization in membranes?

1.0 um

0.5 um

0.22 um (correct)

0.1 um

Why is negative pressure necessary when filtering liquids through membranes?

To avoid contamination during the process

To enhance the capillary action

To increase the gravity flow rate

Because gravity flow rate is slow (correct)

What is the purpose of rinsing glassware with distilled water after washing?

To ensure the glassware is completely dry

To prevent mineral deposits from hard water (correct)

To enhance the visibility of the glassware

To remove excess detergent

Which chemical is used to prepare the cleaning solution for glassware?

Potassium dichromate Signup and view all the answers

What is crucial to do when adding sulfuric acid to the potassium dichromate solution?

Add it slowly with constant stirring Signup and view all the answers

What is the most frequent cause of contamination in pure culture work?

Dust Signup and view all the answers

What should be used to clean dusty objects in the laboratory?

Antiseptic or water detergent solution Signup and view all the answers

When should sub-cultures be made in the culturing of fungi?

As soon as fungi are seen to be growing Signup and view all the answers

What equipment is preferred for culturing fungi in test tubes?

Bacteriological test tubes Signup and view all the answers

What is typically used to plug tubes containing pure cultures of fungi?

Non-absorbent cotton wool Signup and view all the answers

Which of the following is NOT mentioned as part of the general equipment for culturing fungi?

Electrical incubator Signup and view all the answers

Which tool is recommended for picking tiny pieces of fungus for sub-culturing?

Fine forceps Signup and view all the answers

What additional equipment can be utilized in culturing fungi besides Petri dishes and test tubes?

Incubator Signup and view all the answers

What is the purpose of a plug in a tube when used in culture techniques?

To project outside the tube for easy handling Signup and view all the answers

What adjustment must be made to screw caps on bottles during sterilization?

They must be loosened during the process Signup and view all the answers

Which type of dish is described as flat, shallow, and provided with covers of a slightly larger diameter?

Petri dishes Signup and view all the answers

What is the primary function of incubators in fungal studies?

To regulate temperature for maximum growth Signup and view all the answers

Which of the following is NOT a method of heat sterilization?

Chemical Sterilization Signup and view all the answers

What role does the dissecting microscope serve in fungal studies?

To locate and observe suitable groups of spores Signup and view all the answers

What aspect is crucial for using aseptic techniques to prevent contamination?

Operating in a sterile room or hood Signup and view all the answers

Which of the following is considered the most reliable method of sterilization when high temperatures do not modify the sterilized material?

Moist Heat Sterilization Signup and view all the answers

What is the chief mechanism of cell destruction by heat?

Oxidation or coagulation of proteins Signup and view all the answers

Which method is most reliable for sterilizing culture media?

Moist heat (steam sterilization) Signup and view all the answers

What temperature and pressure are typically used in autoclaving?

121°C at 15 psi Signup and view all the answers

What type of sterilization method is suited for metal instruments?

Flame sterilization Signup and view all the answers

How long should materials be exposed to heat during intermittent steaming?

30-60 minutes on each of three successive days Signup and view all the answers

What is a characteristic of dry heat sterilization compared to moist heat?

Requires higher temperatures for longer durations Signup and view all the answers

Which materials are not suitable for moist heat sterilization?

Heat-sensitive materials Signup and view all the answers

What temperature is typically used for sterilizing in a hot air oven for dry heat sterilization?

160°C for 3 hours Signup and view all the answers

What distinguishes disinfectants from antiseptics?

Disinfectants are toxic and used on inanimate objects; antiseptics are non-toxic and used on living tissues. Signup and view all the answers

Which chemical agent is typically used for sterilizing instruments and cultures?

Potassium dichromate Signup and view all the answers

What is the primary action of soap and detergents in the sterilization process?

Disruption of the cell membrane due to decreased surface tension. Signup and view all the answers

What temperature and duration are commonly used for the sterilization of dry glassware in a hot air oven?

160 ̊C for 3 hours Signup and view all the answers

What sterilization method is preferred for porous materials such as culture media and cotton wool?

Autoclaving Signup and view all the answers

Which of the following filters is known for being delicate and should be used carefully?

Cellulose ester membrane filters Signup and view all the answers

What is the main advantage of filtration in sterilization?

It does not change the properties of the filtrate. Signup and view all the answers

Which statement about the sterilization of inoculation needles is true?

They must be held in a flame until red-hot. Signup and view all the answers

Study Notes

General Mycological Laboratory Procedures

Dust is the most frequent contaminant in pure culture work.
Use a towel soaked in antiseptic or detergent solution to clean surfaces.
Remove or clean dusty objects.

Culturing Fungi

To isolate and identify fungi, plate out small samples on many plates (Onions et al., 1981).
Consider the original material and target fungus and contaminants when choosing media.
Do sub-cultures when fungi grow.
Take small pieces of the colony and place them in new sterile media.
Transfer pure cultures to agar slopes in tubes or bottles for storage.

General Equipment

Tubes, plugs, screw-top bottles, petri dishes, incubators are essential
Beakers, flasks (various sizes), measuring cylinders, pipettes, funnels, Bunsen burners, tripods, and balances are required apparatus.
Use suitable markers to label petri dishes and culture tubes.

Other Equipment

Needles, fine-pointed scissors, scalpels, forceps are essential tools.
Dissecting needles (no. 10), fine forceps (Watchmaker's), blades, sharp knives, 70% alcohol.
A dissecting microscope (stereomicroscope) is used to locate spores and observe fungi at macroscopic levels.

Sterilization

Sterilization eliminates all living cells and infectious agents.
Use aseptic techniques to prevent contamination.
Sterilize in a sterile environment such as a sterile room or hood

Physical Methods of Sterilization

Heat Sterilization:
- Moist Heat Sterilization (e.g., steam sterilization, autoclaving)
  - Steam at 100°C
  - Autoclaving (pressure cooking)
- Dry Heat Sterilization (e.g., hot air sterilization):
  - Uses ovens
  - Higher temperatures and longer durations compared to moist heat for dry heat methods.
Filtration:
- Separates microorganisms from liquids
- No change to the properties of the filtrate
- Uses filters like cellulose ester membrane, sintered glass, asbestos pads, unglazed porcelain, and diatomaceous earth disks or candles.
Chemical Sterilization:

Sterilization Techniques

Inoculation needles, loops, and forceps points are sterilized by holding in the Bunsen burner flame until red-hot.
Culture tubes, flasks, bottles, coverslips, scalpels, needles are sterilized by passing through the Bunsen burner flame but not allowing to become red-hot.
Dry glass petri dishes, test tubes, flasks, pipettes, instruments, and glass syringes are sterilized by hot air in an oven at 160°C for three hours.
Culture media, cotton wool, and porous materials are sterilized in an autoclave.
Benches and old cultures are sterilized using a suitable antiseptic (e.g., Lysol).

Cleaning of Glassware

Cleaning is typically done with detergent solutions.
Rinse with distilled water if water has high mineral content.
Use xylol to remove wax pencil marks, paraffin, or other similar substances from glassware before washing.
Use cleaning solution for very dirty glassware.
Cleaning solution preparation involves dissolving potassium dichromate (100 g) in hot water, then adding sulfuric acid (500 ml) with constant stirring. Handle this solution carefully.

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Description

Explore the essential procedures for working in a mycological laboratory, from contamination control to culturing and storing fungi. This quiz covers equipment requirements and best practices for isolating and identifying various fungal species. Test your knowledge on laboratory methods and apparatus used in mycology.