I'm not expert on the area but cell surface charge is usually measured by zeta potential. In the not-so-recent review linked below, authors include a section regarding aqueous two-phase partitioning.

Article Status of Methods for Assessing Bacterial Cell Surface Charg...

... yes Xavier, thank you. I have seen this one. This ad and similar approaches seem to go back to a 1974 publication by Göte Johansson. This probably works, but I still hope for something with less bench work. - There is alway hope!

Dear Johannes

Do you just want to know the net charge? then hope and creativity could bring light to your question

If you want to quantify the charge, then as far as I know, we need bench work. Zeta potential seems the best standard test

good luck (is this for donstream separation?)

Xavier

Probably the easiest method would be using a Zetasizer. You just need to resuspend the cells in a solution, but you have to have access to the equipment.

@Xavier ...numbers are what I want! Don't worry, I do not believe too much in hope and esoterics or similar .... life has always been labour, and so it will be also today, I fear. :-)

Thanks for bothering - Johannes.

(no it's for comparing modified cell surfaces, not for processing of all sorts.)

It probably won't be identical for all bacteria but this paper might be useful. Yoram 

Soni et al. 2008 - Zeta Potential of Selected Bacteria in Drinking Water When Dead, Starved, or Exposed to Minimal and Rich Culture Media

http://link.springer.com/article/10.1007%2Fs00284-007-9046-z

Great Yoram, I didn't know that one. Thanks a lot.

Pleasure!

Dear Sir,

You may please refer to the links below:-

1. http://www.sciencedirect.com/science/article/pii/S0167701200002244

2. http://aem.asm.org/content/65/7/2877.full

3. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC92652/