Emlyn wrote:
> She knows a bit about bacteria. We've talked about cells & other little
> things too... I'm going to get my hands on a microscope ASAP.
I'd concur with others Emlyn, if you are eductating her about bacteria
and she understands them at the age of 5, you are doing a great job
as a parent.
Regarding getting a microscope, you might want to consider the Intel
computer microcam, I think it has a microscope "attachment", however
I'm not sure it would be sufficiently powerful to see bacteria. You
probably could do yeast which are ~10x bigger or some cyanobacteria
that you could find in pond water get pretty big. You will need to
go to 400x perhaps 1000x to see bacteria if I recall correctly.
Unfortunately, bacteria being around a micron in size are at the limits
of far-field visible light microscopy because they are only slightly
larger than the wavelengths in visible light (400-700 nm).
To view bacteria most effectively, they also need to be stained.
Standard microbiology uses an iodine stain, with an alcohol flush
followed by a safranin stain to differentiate between gram negative
and gram positive bacteria (they have different cell wall molecules
that have different stain affinities).
>
> Anyway, I've told her about plaque in your mouth, and how it is bacteria
> chomping on your teeth, which are promoted by sugary foods. I could be
> wrong about that, I've just been pedalling the standard parent party line.
Nope, for once the party line is correct. The bacteria are consuming
sugar and producing acid that attacks your teeth. They are proabably
doing this to provide a pocket in which they can live more safely
protected from your toothbrushes, bacteriocidins in your saliva,
roaming macrophages, etc. They could also be harvesting the minerals
but I think that would be of lower priority.
There is a Dentist(molecular biologist?), I believe from Florida,
who has engineered a strain of Streptococcus mutans (the primary
culprit in tooth decay along with Streptococcus sobrinus, so that
it does not produce the decay causing lactic acid. I believe they are
intending to take this to clinical trials. The strategy is to infect
your mouth preferentially with the "good bacteria" so the bad
bacteria have a harder time of it.
>
> Also, she knows that sugar is used as a preservative in foods, like jam.
...
> If sugar is a preservative, and stops bacteria from eating food,
> why does it cause decay in teeth, which is due to promotion of bacteria?
The sugar question has been addressed correctly. At high concentrations
molecules like sugar and salt function to extract the water from the
bacteria by osmosis.
> Another piece; she interogated me recently about food rotting; why does it
> happen? I told her that bacteria eat it.
That is to some degree true, but only on surfaces exposed to air.
Internally meat, chicken, eggs, etc. "should" be bacteria free.
However, the preparation process if not done well, can contaminate
it with things such as E. coli, Salmonella, etc. The problem
involves how to butcher an animal without contaminating the meat with
the contents of the digestive tract or other surfaces that are likely
to harbor bacteria.
Now to some extent cells are always "self-digesting", there is a good
article on the "proteosome", "The Cellular Chamber of Doom", in
Scientific American, Jan. 2001, pg 68. This machine functions to
break down proteins for recycling. The typical figure I've seen for
protein turnover in the liver is ~1%/hr (increasing when you are on
caloric restriction). You also have RNAse's and DNAse's that chop up
RNA and DNA for recycling. I'd have to dig through the biochemistry
books for a while to see which of those processes require ATP and since
I've got other things I need to do today that is left as an exercise
for the reader :-). If those breakdown processes are biochemically
favorable, then they would occur in cells even when the animal is dead.
Lacking a fresh energy supply (sugar from the bloodstream), new
proteins and RNA cannot be synthesized (for these do require ATP
derived from sugar) and thus the cells "eat" themselves.
The bacteria probably attack from the outside, but the cells
are probably consuming themselves from the inside as well.
For those who are really interested in exploring the "nanoworld",
culturing of bacteria is a great way to do it. Its something
most people on the list should do at sometime or another as
a self-education exercise. You need agar plates (something I've
seen at a local science education store here in Seattle),
a Bunsen burner of some type (I suppose the real men like Mike
can use a propane torch...), a glass rod with a metal loop,
some swabs for collecting and spreading the bacteria on the
agar plate and transfering them to a microscope slide and
of course the microscope. I would have to believe there are
sites on the net for "Introduction to Microbiology" that explain
the experimental procedures involved.
The interesting thing is that bacteria are "almost" everywhere.
You can leave an agar plate open to the air and you will have
bacteria of several types growing in it after a few days.
Then your mouth is a hotbed of bacterial activity. Even if
you don't have a microscope, you can grow visible colonies
on the agar plates. As Robert (here are the numbers) Freitas
points out in Nanomedicine, Section 8.5.1, pg 247 (I know
there are some of you out there that stopped after Chapter 3,
thus missing some of the "good" parts...), there are ~40 trillion
foreign organisms, mostly bacteria in or on the human body.
Given that most of your cells are red blood cells that do not
contain DNA, this means that there are almost 10x as many
copies of foreign genomes in your body as there are copies
of your genome. Those genomes contain ~10x fewer genes
(~3-4000 vs. 30-40,000) than your own genome does.
Well, enough trivia for today.
Just to satisfy my curiosity, could one or two people confirm
to me (off-list), that they did in fact see my post re:
SPACE & Interstellar Travel:
http://www.lucifer.com/exi-lists/extropians/2511.html
I would have thought it would have drawn more commentary
but perhaps it just got lost in the holiday chaos.
Robert
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