For what it is worth, Neidhardt et al. do list a figure for the dry weight of a
single E. coli cell in their microbial physiology text." The figure they list
is 2.9 E-13 g. The do not include any citations for this figure specifically,
but they do state that it is "an average of many measurements..." Neidhardt,
F.C., J. L. Ingraham, and M. Schaecher. 1990. Physiology of the Bacterial
Cell. Sunderland, Mass: Sinauer Associates.
Would you like the mailing address for that egg?
Incidentally, who said that the largest viruses are larger than the smallest
bacteria? I have to admit, I know little about viruses, but I can hardly
believe that statement is true. What virus is as large as a bacterium?
Em wrote:
> ...or, very roughly for E.coli, the culture at OD660 ~0.5/cm contains ~10^9
> cells/ml or ~1g/l of dry cell mass. Given the weight of a cell is ~50% water
> (very roughly indeed), the mass of a single cell is 1*2/10^9 ~ 2ng. 10 times
> difference with Graham's calculation is most probably attributed to
> inaccuracies of our assumptions of 1) size, 2) cell number (in particular 2
> cells can be counted as 1), 3) density of the cell, 4) content of water. Of
> course both dry weight and content of water per cell can be accurately
> determined using standard techniques.
>> Emir
>> "Graham Shepherd" <muhero.nospam at globalnet.co.uk> wrote in message
> news:a8g9gm$b05$1 at helle.btinternet.com...> > Smarty <smartman at comcast.net> wrote in message
> > news:3cab7bd6.18969629 at news.in.comcast.giganews.com...> > > Less than 500 milligrams
> > >
> >
> > An unusually unhelpful response.
> >
> > You can get an approximation by calculating the volume of the organism
> from
> > typical dimensions (eg for E.coli assume it's a cylinder 1 micron long
> with
> > a diameter of 0.5 micron) and assume that the density is the same as
> water.
> > (It is greater, otherwise you couldn't spin them down - but it's probably
> > not much greater. You could determine the density on a gradient if it's
> > critical).
> >
> > A rough calculation indicates that the volume is about 0.2 cubic microns.
> > That's 5,000,000,000 per cubic millimeter, or 5,000,000,000,000 per cubic
> > cm. Assuming 1 gram per cubic cm, one bacterium weighs about 0.2 picogram.
> >
> > Viruses are much more variable in size than bacteria (the biggest viruses
> > are bigger than the smallest bacteria). But you could do the same
> > calculation for a specific virus.
> >
> > GS
> >
> >
> >
> >
