Monitoring cell activity using substrates, which turn fluorescent due to biological activity, allows observing the presence and dynamics of sub-populations, and provides a very valuable insight in ecological studies. The phosphatase substrate ELF97 phosphate (ELF-P) is a useful tool to detect and quantify phosphatase activity (PA) of microorganisms at the single-cell level. Most of the studies dealing with PA at the single-cell level focus on autotrophic cells and only few concern heterotrophic prokaryotes (referred as bacteria in the text). While flow cytometry is a promising tool to assess the single-cell analysis, only microscopy tools have been used until now to measure the ELF labeling associated with bacteria expressing PA. Therefore, we have developed a new protocol that enables the detection of ELF alcohol (ELFA), the product of ELF-P hydrolysis, making possible the specific identification of bacteria showing PA using flow cytometry. Keywords:
