Table of Contents

My Body in Space – Bugs In My Glove

Unit #2: The Biology of EVA Gloves, Bacterial and Moulds

Student Investigation

Objectives

The primary objectives of this activity are:

1. To demonstrate that human hands provide a robust source of bacteria, which under suitable conditions can reproduce to form large bacterial colonies.
2. To consider techniques whereby the growth of bacteria (and other microorganisms such as moulds) can be prevented (or at least minimized).
3. To test various household disinfectants for their ability to prevent bacterial growth.

Safety

It is possible to culture some unpleasant (nasty) bacteria and moulds, therefore, all cultured species should be treated as potentially dangerous. When performing any experiment which involves such cultures follow these simple safety rules:

1. Never open sealed containers containing your cultures.
2. Dispose of them using the "two-step" method.
   i. sterilize your samples, either by heat sterilization (in a suitable autoclave) or
      immersion in a diluted solution of water and chlorine bleach.
   ii. place the sterilized samples in a plastic garbage bag and tie it securely for
      disposal in regular garbage collection.
3. Always wash your hands thoroughly after handling any samples, even if they have been sealed.

Equipment

1. A pot of boiling water (Always use caution when working with boiling water. Safety goggles are recommended.)
2. A culture medium i.e. a few potato slices (or Petri dishes and a suitable Nutrient agar)
3. A small kitchen knife that can be used to slice the potatoes. (again, use caution with knives)
4. Tongs
5. Self-sealing clear plastic food storage bags, sandwich size (such as "ZipLoc" bags).
6. Sterile cotton swabs (such as Q-tips).
7. Assorted commercial disinfectants (Lysol, Comet, Vim etc.).

Procedure

Note: This procedure applies to the technique which uses sterilized and inoculated potato slices as the growth medium for the bacteria culture. If you are using Petri dishes with Nutrient agar you should follow the directions appropriate for this technique.

1. Prepare the culture medium (thin slices of potato - approximately 2 to 5mm thick is ideal). Immediately prior to use, plunge the potato slices into boiling water for about 30 seconds. This will sterilize the surface and also cause the potato cells near the surface to split open, making it easier for the bacteria to proliferate.

   
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2. Place one slice on top of each plastic food bag. One for each culture that you wish to investigate. (Use only one swab and one potato slice for each sample).

   
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3. Take a sample from each of the following sources:
   i. the ends of the finger;
   ii. under the fingernails;
   iii. the palm of the hand;
   iv. the back of the hand;
   v. the door handle;
   vi. the handle of a pencil sharpener.
   

   

4. Use a sterile cotton swab to transfer bacteria from the source to the top side of each potato slice. It helps to trace out the shape of a letter such as E or A with the swab. This will help distinguish between the growth of any airborne opportunistic bacteria that have landed on the potato slice and those that you have deliberately inoculated onto the slice.

   

5. Place one set of samples in a cool dark location.
6. Place a second identical set of samples in a warm location.
7. Observe and record changes each day for two to three weeks.

   
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Student Investigation Activities, Extensions – Sterilization Studies

For space flight activities it might be very useful to develop a sterilization protocol so that the ability of bacteria and moulds to flourish is inhibited.

1. Investigate various methods of inhibiting bacterial and mould growth. Prepare several culture samples and treat each culture medium with a different commercial antibacterial agent. Be sure to culture a control sample so that you can evaluate the results.

2. Test the effects of acidic solutions on the growth of bacteria. Undiluted vinegar is quite acidic.

3. If an ultraviolet light source is available investigate its effect on bacterial growth. Illuminate samples for various lengths of time and at various times during the culture growth. Compare the results with an unexposed control sample.

Based on these studies write a proposal for a practical sterilization protocol that might be applied to the hand and gloves of EVA astronauts prior to their EVA deployment.