That.
If doing what you are doing depends primarily on extrinsic rewards, it sucks.
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Looks like a somewhat more even distribution than randomness would cause. I suppose that lends some support to the idea that good critters can crowd out bad critters.
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Correct me if Iâm wrong, but, wouldnât it be equally compelling evidence for hands having wrinkles and creases?
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Actually, agar is a polymer made up of subunits of the sugar galactose, and a few seaweeds (primarily of the genus Gelidium) just happen to be a convenient source. [Iâm considering a run at a pedant pendant.]
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One of my lab jobs was to make blood agar plates for diagnosing strep infections. Once a week weâd get a couple bottles of fresh rabbit blood, and you had to be careful not to overheat the blood or it would coagulate. Done right, the whole room would smell like fresh warm blood.
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If you cannot preserve and keep it somehow, whatâs the point of the hand-sized version!?!?!?
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A relative of mine used to do this, when he worked for the Ministry of Agriculture. Being a religious type, he wondered about the implications of the phrase âwashed in Jesusâ bloodâ, and tried washing various items in blood. Apparently it works better than you might expect.
Iâm a bit disappointed he didnât get round to âThere is a fountain filled with bloodâ.
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Old joke (told me by an Australian ex-pat): âWhatâs the difference between Australia and Agar-agar? Agar-agar develops a culture.â
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Many of these bugs are involved in a mutually beneficial relationship with their human hosts - many of which are not fully understood. Antibac soaps are quite well understood - and they are at best useless, and at worse harmful.
http://cid.oxfordjournals.org/content/45/Supplement_2/S137.long
Washing hands is of course, a good thing, killing all these micro-beasts dead probably isnât.
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My mother never let me play in an agar medium, but she did show me that if you put a piece of bread in a jar with a little water and stick it under the sink itâll grow mold. I thought this was so cool I had at least three jars of different stuff under the sink at any time. My mother told everyone I was going to be the next Jonas Salk.
I am such a disappointment.
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Man, I donât want to know what the room would smell like if it was done WRONG.
And yet, most people are going to see this and think âAhh! I must Purell⢠my childâs hands at every opportunity now!â The way I figure it, the more acquainted my kid becomes with these bugs, the better off theyâll be in the end. Be friends, not enemies!
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Each solid-colored circle represents a colony started by a single bacterium. The image shows that there were dozens of bacteria on the childâs hand. Like a lot of people, I would have guessed that there were millions.
Of course, not all would have transferred to the medium. But the lesson here is that the number of bacteria on the hand of a child who has been playing outside is much smaller â by orders of magnitude â than you would think.
When people express shock and horror at the image, itâs because they thought there were none at all. (âDonât call them âbacteria skepticsâ â theyâre bacteria DENIERS!â) Is it a surprise, two centuries after Pasteur, that we are largely bacteria deniers? After all, the notion â tiny invisible creatures that can make you sick â is ridiculous on its face. Though true.
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When I hear the word culture âŚ, I release the safety on my Browning!
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The ones on your face are even worse than the ones on your hand!
And the teeth, the teeth!
âŚactually, a human bite can be pretty dangerous, as this guy may attest toâŚ
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And not all would grow on the chosen medium at the chosen temperature. Some would have been swamped or inhibited by others growing near them. Some colonies might still be too small to see. Some might not be viable.
I donât know if there are any counts of the number of bacteria on childrenâs hands, but I do know that counts of bacterial cells in soil have found about a billion (10^9) per gram of soil.
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How do I create a medium like this to teach science with my 9 year old daughter?
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Hereâs a link to a University of Utah page that looks like it would be really helpful: http://teach.genetics.utah.edu/content/gsl/html/agar.html
Seems pretty in depth and looks like it was written for a lay audience.
And hereâs a page it links to with recipes for different types of media that you can use: http://teach.genetics.utah.edu/content/gsl/html/recipes.html
They warn against using gelatin because it melts in a 37C incubator, bacteria can digest it (they canât digest the agar medium, just the sugars in it), and gelatin doesnât set well in high salinity solutions (10% NaCl or more).
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