Many years ago we used Raper's method to label amoebae with Serratia. It
seemed to be a hit-or-miss affair at first. Later we found that it wasn't
difficult to select for Dd clones that showed a strong red/orange colour.
While doing those experiments R Baskar discovered something very useful
along the way: neutral red is an excellent fluorescent marker. He reported
it in his thesis.

Neutral red stains all amoebae at the freshly starved stage or even later.
Initially slugs too show a uniform red colour which changes over time to
the characteristic prestalk staining pattern (Bonner, Am Natur 1952). But
that is just the visible pattern and is very likely due to vacuolar pH
differences between pst and psp cells (Yamamoto and Takeuchi,
Differentiation 1983) - similar to the basis of MacConkey agar. Neutral
red fluorescence can be seen in all cells, whether pst or psp, and is
therefore an excellent marker for tracking cell fate.

Vidyanand Nanjundiah

Developmental Biology and Genetics Laboratory
Indian Institute of Science
Bangalore
India

in the past

> Dear Dicty Colleagues,
>
> I am trying to track the cell fate of Dicty cells with Serratia
> marcescens, but found that the pigment was not retained in the amoeba or
> slugs. The bacteria produced intense red color when plated. I was just
> wondering if any of you have used Serratia in the recent past and have
> been successful in getting red colored slugs. I would appreciate it, if
> any of you could tell me if there are any specific strains or subtypes of
> Serratia that I need to use. Eagerly awaiting your comments.
>
>
> Regards
> Prasad
>
> Developmental Genetics Laboratory
> Department of Biotechnology
> Indian Institute of Technology-Madras
> Chennai,India.
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