# mass of bacteria

Graham Shepherd muhero.nospam at globalnet.co.uk
Mon Apr 8 13:45:00 EST 2002

```Nicholas Landau <njl2q at virginia.edu> wrote in message
news:3CB11E37.D05743F9 at virginia.edu...
>
> 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.

So the dry weight is 0.29 picograms - if wet weight is about double the dry
weight that makes it 0.6 picograms. My original very crude estimate was 0.2
picograms. Do Neidhardt et al also publish average dimensions and density?
If so, we can recalculate using a formula for a cylinder with hemispherical
ends and see how close a derived weight is to a measured value.

GS

> 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
> > >
> > >
> > >
> > >
>

```