[extropy-chat] Resources for microscopes

[Martin Striz]

On 4/2/06, kevinfreels.com <kevin at kevinfreels.com> wrote:
>
>
> My daughters and I want to get some petri dishes and collect samples from
> what is flying around in the air in the house and see if there is mold and
> other such things. We plan to collect samples in some kind of medium in the
> dishes and culture it so we can get decent samples for microscopes. Then we
> would like to look at it in the microscope and find out what we have. It
> should be a fun experiment for us all.

> Does anyone know what kinds of media I should use for collecting and
> culturing the samples? Or, does anyone know of a website resource for
> comparing samples with photographs?  Our main concern is that we have
> Strachybotrys running around, but others may be present as well.

I taught several semesters of college microbiology, so I might be of
some assistance.  If you want to "find out what you have" to the level
of identification, basic morphology won't be enough.  In fact, you
won't see too much interesting stuff with bacteria (cocci vs bacilli,
tetrads vs. chains, at best).  With fungi you get some interesting
colors (blue, green, black even) and smells.  I can predict that
you'll get a nasty smelling green mold, which is a common bread
fungus.

Furthermore, you won't see much with bacteria at all unless you
purchase some STAINS.  Light passes right through single cells them
leaving them almost invisible.  There are basic stains that you can
apply to bacteria, and then more involved ones like the Gram stain or
acid-fast stain (several reagents and steps).  These also allow for
some differentiation (E. coli is gram negative, for examle.).

Identification will require selective media on which to subculture
your colonies.  You can get guides -- if nothing else, a college
microbiology lab textbook from Amazon.com.  Microbes have different
nutritional and environmental requirements, so before gene sequencing
technology, microbial identification consisted of going through a
heirarchical series of growth media until you narrowed down what you
had to a specific genus or species (kind of like identifying a tree
with one of those guides that asks a series of questions about the
leaves).    These media can have different sugars (lactose vs sucrose
fermentation), blood extract (hemoglobin lysis), chocolate extract
(highly enriched for fastidious organisms), and a lot of other
nutrients, pH content, salt, anaerobic conditions, enzymes, etc.  Some
of them come with indicators that turn the medium yellow, red, purple,
green and in one case hot pink (something your kids might enjoy).  I
don't know if that's the level of analysis that you want, but there it
is.

Not sure if and how many of those selective and differential media are
available to the public, versus exclusively for research purposes, but
you can inquire with the relevant companies.  I don't know any by
name, since we had a tech prepare all that stuff.

You may not want to invest that much in bacterial identification. 
Fungi provide you better colony morphology as I mentioned before, and
fungi constitute most airborn microbes, from my experince.  Bacteria
don't survive dessication (neither does any cell), but fungi form
spores to survive.  Luckily, therefore, that most fungi aren't
pathogenic to man.

I know that basic growth medium is available online for sale to the
public.  Look for agar (or agar extract).  Fungi often grow better on
YPD medium.  Both might be available in enriched forms, although you
probably won't need it.  Just leave the petri dishes exposed for a
couple of minutes (maybe hours but if you overdo it,  you'll get
undifferentiable growth all over the plate).

As for photographs, the lab manual that I taught out of was by
Cappuccino and Sherman (ugly long URL:
http://www.amazon.com/gp/product/080532836X/sr=8-1/qid=1144032711/ref=pd_bbs_1/103-1138016-3497412?%5Fencoding=UTF8)
and we had this Photographic Atlas available in class
(http://www.amazon.com/gp/product/0895826569/ref=pd_sim_b_4/103-1138016-3497412?%5Fencoding=UTF8&v=glance&n=283155).
 Sorry if that's too high level, but those are the best (i.e. only :)
sources I know.


Cheers,
Martin