[Microbiology] Re: science project

GS not at home.com
Fri Aug 25 15:34:25 EST 2006


"Gardner, Catherine (DHS)" <catherine.gardner at dc.gov> wrote in message 
news:mailman.757.1156535116.20007.microbio at net.bio.net...
> Hello,
>
> My son is doing a science project.  we will be taking swabs of certain
> surfaces to see what is growing on them.
>
> what shoud we use and where can we buy these materials.
>
> help !
>
> a very thankful mother.
>
> ladyg32 at hotmai.com <mailto:ladyg32 at hotmai.com>

This is one of these "Don't try this at home" scenarios. To do this type of 
work safely, you need a fair amount of background knowledge and a few fairly 
simple techniques. You can find that in most introductory microbiology 
books.

Just because something is found on a surface, it doesn't mean it's growing 
there, and some of the things you might grow are dangerous in the numbers 
you will get by culturing them. For example, if you sample surfaces that 
people have been touching, you will find staphylococci without having to 
look too hard. The school (or whoever designed the project) should be able 
to give you advice. However, if you do go ahead, make sure you contain 
everything you grow and disinfect everything when you're finished (by 
incineration or by total immerson in strong bleach).

For laboratory use there are specially designed agar contact plates which 
you press against the surface you are sampling and then incubate. Before 
there were agar plates, Robert Koch used the cut surfaces of various things 
(eg potatoes, animal eyes) as culture media.

You don't need to grow things to be able to study micro-organisms. With a 
microscope you can do direct observations on samples from tongue or tooth 
scrapings, yoghurt, cheeses like brie or camembert, soil or rainwater, 
samples of leaves in the garden (especially if they are damaged or look 
sick). You'll find a whole range of things from bacteria and moulds up to 
protozoa and beyond. Some things will need preparation ( eg fixing and 
staining) to get the best results.

GS 




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