Very Quick Cell Question

Anthony J. Pelletier Ph.D. anthonyp at scripps.edu
Tue Feb 17 17:26:07 EST 1998


TODD J PIERCE wrote:
> 
> I know I can see individual strands of bacteria at 100x with a microscope.
> 
> My question is this what magnification do I need to see both a cell and
> its nucleus--that is, for a fairly large cell--200x, 500x?  In our very
> basic lab, we have microscopes up to 100x.  Are microscopes with higher
> ranges of magnifacation common in working labs?
> 
> Could I see the nucleus with the standard microscope, or can one only see
> the dark outline of the nucleus with an electron microscope?
> 
> Thanks,
> Todd


Ok, I'll ask the obvious question: are you talking about eukariotic cells,
which have "true" nucleii or are you still talking about bacteria, which lack
true nucleii? (many bacteriologists will still refer to the "nucleoid body" or
whatever as the "nucleus;" the semantics of this are not really important.  I
just want to make sure I answer the right question).

If eukariotic cells are the subject and you want to see the outline of the
nucleus during metaphase, a decent phase-contrast scope will suit fine. 
Magnification of 100X will also be fine for this.

Now, if you want to see the nucleoid body (that is, the chromosome) of a
bacterial cell, you will more magnification (say, 300x or so) would be helpful
and you will need to do something to make the DNA stand out.  Another poster
suggested a fluorescent dye, which is the best approach, although I wouldn't
use ethidium bromide (DAPI or one of the Hoescht dyes are better for
epifluorescence).  This will require a much more elaborate scope, since you
need to have the ability to hit the cells through the objective itself with
the excititory wavelength to see them (that is what's called "epifluorescence").

Finally, as for what a "working lab" might have, it really depends on the
style of research.  I would say that a phase scope with magnification around
200-300x is commone to any lab doing mammalian cell culture.  More elaborate
optical systems also are common depending on the focus of the lab.  eg, any
nematode lab (the nematode C. elegans is a really popular developmental
genetics model) will have one or more scope equiped with differential
interference contrast (or "Nomarski") optics and magnifications out to 300X or
more.  These same scopes often are equiped for epifluorescence.  Even more
elaborate setups like confocal microscopes are getting more common. 

-- 
-tony


*********************************************************

Anthony J. Pelletier, Ph.D.
Assistant Professor, Department of Cell Biology
The Scripps Research Institute
Mail stop SBR12
10550 North Torrey Pines Rd.
La Jolla, CA 92037
(619) 784-9760

anthonyp at scripps.edu



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