hanging drop

sterile

• No living microorganisms in or on something 

• Nothing is sterile unless you or someone else has sterilized it 

Sterile technique 

• Aka aseptic technique 

• Performing an action in a way that minimizes the chances of contamination of a sterile object 

Inoculate 

to Intentionally introduce a microbe into something 

Contaminate 

To accidently introduce a microbe into something 

Culture 

a population of bacteria 

Pure culture 

• a population of bacteria that are all genetically identical 

• generally, they are all descended from a single progenitor 

Media 

• What we grow our microorganisms on 

• Contains various nutrients that the microbe requires for growth 

• Liquid media 

• Aka broth media 

New equipment that we used for hanging drop

• Concavity slide (depression slide) and coverslip 

• inoculation loop or transfer loop 

• test tube or culture tube 

• incinerator 

 

 

Hanging drop method 

• Used to look at live microorganisms 

• The microorganisms are unstained. 

• Most unstained microorganisms are colorless 

• Will often appear black or gray 

• Sometimes can appear brighter than their surroundings  

Be able to describe the procedure to prepare the slide step 1

• Place 4 drops of petroleum jelly on the concavity slide 

• On the side with the depression 

• Adjacent to the depression 

step 2:

• Using a loop, place a drop of culture on a cover slip 

• Loop must be sterile before transferring the culture drop 

• To sterilize, hold the loop in the incinerator until it glows red 

• Allow it to cool briefly before inserting it into the bacterial culture 

step 3:

Turn the concavity slide depression side down so that the petroleum jelly is facing down

step 4:

• Gently place the slide on the coverslip so that the drop of culture is in the middle of the depression 

• Turn the slide right side up so that the coverslip is now on top and the drop of culture is hanging off of the coverslip 

What can go wrong 

• Too much light or too little contrast 

• Slide too old 

If any of your sample is motile, then you call the result motile 

• Some microbes get stuck to the glass and stop moving 

• Some microbes may be dead 

• Only if none of your sample is motile do you call the result non-motile 

Clean-up 

• Remove the coverslip and drop it into the kill jar containing disinfectant 

• Submerge the concavity slide in the kill jar and then rinse it and dry it off. Return it to the slide box. Do NOT throw away the slide.