# mass of bacteria

Larry Farrell farrlarr at isu.edu
Tue Apr 9 10:10:58 EST 2002

```Again, as posted yesterday, some of the smallest cocci are 0.2 nm in diameter and
smallpox virus is 0.2-0.3 nm x 0.25 nm.

Nicholas Landau wrote:

> The largest viruses are bigger than bacteria?  Which virus?  I never heard
> that (but then, I never studied virology).
>
> --Nick
>
> Graham Shepherd wrote:
>
> > 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

--
Larry D. Farrell, Ph.D.
Professor of Microbiology
Idaho State University

```