bacteria and protozoan relationship

Tue Feb 28 08:19:29 EST 1995

Donald Suess Wrote:

>I stain various bacteria with DTAF,feed them to various protozoans and 
>look at the results under a fluorescent microscope. Interesting results. 
>Anyone interested?

Masahiro Fujishima Wrote Back:

>What is DTAF?

        DTAF is a green fluorchrome that stains proteins, a derivative of
FITC (look them up in a SIGMA catalog).  The described procedure is a
standard technique used to study phagotrophy in macrophages and free living
protists.  Although probably first used in medical research, it has been
popularized in ecological literature by E. Sherr & B. Sherr (now at Oregon
State U) as the "fluorescently labeled bacteria" (FLB) procedure.  It is
generally a good technique for studying ingestion rates, but be cautioned
that the staining procedure probably affects surface chemistry which is
potentially important to bacteria:protist interactions, especially with
amoebae and flagellates.  You might try staining a variety of bacterial
species and see if the ingestion rates are at all related to the growth
rates obtained (which will vary considerably) on the individual species of
bacteria.  Be careful with ingestion data, as it follows a poisson
distribution and needs to be transformed for slope estimations by
regression and statistical comparisions based on normal distributions or
use nonparametric techniques.

        The technique is especially useful for teaching purposes.  Try
mixing light (phase) at very low power and fluorescence microscopy with
living cells in wet mounts with FLB's.  Also try mixing colors. 
Fluorescently labeled latex beads are also good for this purpose, and
retain their fluorescence longer under continued excitation with the
mercury bulb.  Have Fun!!

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