Something is not right. The Klett vs. time curve which started me on this was
published in J.Bact. 181:3649-3657 (Federle, et. al.) This is Group A
Streptococcus in an unidentified Todd-Hewitt preparation. Stationary phase is
entered at Klett 100. Koch, A.L. tells us this is Abs = 0.2. Having grown
equivalent strains in three different commercial preparations of Todd-Hewitt, I
know they typically grow up to Abs = 1.5 or so. I am being pedantic to some
degree, but I can mathematically define absorbance and transmission; I am in the
dark still with the definition of a Klett. The curves in this particular paper are
useful, they show the relative rates of growth of three strains, I cannot compare
them directly to my own curves though.
Why do not we use nephelometry to measure the concentration of our
bacterial suspensions? From what I understand, it is more sensitive
at the lower concentrations, and hence might be useful in generation
lag phase curves. Nephelometry measures the intensity of scattered light
at a right angle to the sample and the light source. Scattered light
is proportional to the intensity of the light source (not so in a turbidometric
set up measuring transmission - light source, sample, detector in a linear
arrangement).
Andrew Heath
Research Associate
University of Michigan
Infectious Diseases
: According to A.L. Koch in "Manual of Methods for General Bacteriology",
: ASM Press 1981, p 197, 500 Klett units corresponds to an Absorbance
: of 1.0.
Thanks for a textual reference, alas that text is not in the University of
Michigan in Ann Arbor's Library.
: Raymond Cox
: Institute of Biochemistry
: Odense University, Denmark
