I would like to monitor phagocytosis of our Gram negative bacteria by flow cytometry.

I already tried to generate a GFP-expressing bacteria, but even with the strongest promotor we have so far the fluorescence was too weak to be seen properly by the flow cytometer.

Thus I would like to stain the bacteria with a fluorescent dye that would allow to be followed for around 2 hours and most importantly affect the physiology of our bacteria as less as possible.

Do you have any recommendation ?

I already used TRSE staining for visualization by microscopy but given the number of mutants I need to test I would really like to have a dye that can be read by a FACScalibur to perform a first screening.