z*******6
发帖数: 679 | 1 为什么不用500？400？或者其他的？有文献参考吗？是不是有人最早做了整个spectrum
，然后发现600最好，就用了？...
google了一下没找到想要的答案，不知道大家能不能帮我解答一下...谢谢！
有点钻牛角尖的感觉，出不来了... | b******y
发帖数: 627 | 2 As particles around a micron, these scatter light at 600nm, 500nm, or 400nm.
My guess bacteria don't have pigments that absorb at 600nm but does have
pigments that absorb at these lower wavelength.
Just my guess. | h**********r
发帖数: 671 | 3 You can scan the OD of the culture by using UV-Vis spectrometer, and then
pick up the wavelength at peak. Determine the CDW (cell dry weight) Vs. OD
at selected wavelength, and make a curve.
For some microbes, it's different. For some green microalgae, some one uses
OD770. For cyanobacteria, people use OD750 or OD730. For some orange conidia
from the fungus, OD420 is used.
| z*******6
发帖数: 679 | 4 Thanks. This is what I was thinking. But this still leaves the question, why
they have the peak at 600 nm for most bacteria.
I guess the 2nd floor gave me a little hint, which I just leaned last
semester but already forgot...
uses
conidia
【在 h**********r 的大作中提到】
: You can scan the OD of the culture by using UV-Vis spectrometer, and then
: pick up the wavelength at peak. Determine the CDW (cell dry weight) Vs. OD
: at selected wavelength, and make a curve.
: For some microbes, it's different. For some green microalgae, some one uses
: OD770. For cyanobacteria, people use OD750 or OD730. For some orange conidia
: from the fungus, OD420 is used.
:
| h**********r
发帖数: 671 | 5 How about this answer?
From http://molecularbiology.forums.biotechniques.com/viewtopic.php?f=5&t=15007
When measuring light scattering it is important to consider the wavelength
of light used a bacterial culture. Microorganisms may contain numerous
macromolecules that will absorb light, including DNA (254 nm), proteins (280
nm), cytochromes (400-500 nm), and possible cell pigments. When measuring
bacteria by light scattering it is best to pick a wavelength where
absorption is at a minimum and for most bacterial cultures wavelengths
around 600 nm are a good choice. However, the exact wavelength chosen is
species specific.
In fact, it's difficult to detect the cell biomass accurately. The microbes
have many different growth profiles such as pellets, mycelia,(ac)spores,
conidia. Some fungi are mating each other. Some bacteria produce pigments
and other colorful metabolites. The photosynthetic microbes have chloroplast
. Usually, the cell dry weight is more widely accepted. Sometimes we also count the cells under microscope. Some people use agar plates to count the living cells.
But when cells grow in the media containing solid residues like straw, and cells and the residues are attached/packed together, it's hard to know the dry weight of
cell biomass/digested straw. People use protein/DNA/Nitrogen/Carbon content to determine the cell biomass, but it's time and labor consuming.
| z*******6
发帖数: 679 | 6 I think this is enough for me... Thanks a lot!
280
【在 h**********r 的大作中提到】
: How about this answer?
: From http://molecularbiology.forums.biotechniques.com/viewtopic.php?f=5&t=15007
: When measuring light scattering it is important to consider the wavelength
: of light used a bacterial culture. Microorganisms may contain numerous
: macromolecules that will absorb light, including DNA (254 nm), proteins (280
: nm), cytochromes (400-500 nm), and possible cell pigments. When measuring
: bacteria by light scattering it is best to pick a wavelength where
: absorption is at a minimum and for most bacterial cultures wavelengths
: around 600 nm are a good choice. However, the exact wavelength chosen is
: species specific.
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