Flow cytometry offers a powerful way of looking at the single-cell properties of microbes, particularly useful for those microbes that inhabit aquatic environments. Size, DNA content, membrane state, respiratory and enzymatic activity can be determined with relative ease and with the help of physiological probes. I will present experimental evidence of some of these probes and the necessary tests to validate them, including the use of flow cytometry cell sorting coupled to 454 pyrosequencing of the 16SrDNA gene. The determination of these properties in hundreds of cells per second allows the calculation of several indices of ecosystem state based on the physiological structure of the planktonic community determined with the probes, and I will review how this structure varies among ecosystem types, from the most oligotrophic oceanic waters to those of eutrophic or brown lakes. Finally, and since flow cytometry also allows the detection of different types of photosynthetic microbes, I will extend the idea of “physiological structure” to the concept of “cytometric structure”, in which we consider the presence of specific populations, the number and position of the different populations, the cytometric diversity and some population abundance ratios that allow the calculation of indices of ecological function that can be used to test for the health of aquatic environments. The easy of use, affordability and transportability (including the existence of in situ machines) of flow cytometers make these techniques serious and robust candidates for the standard monitoring of aquatic environments based on the structure and activity of planktonic microbes

71st Annual Congress of the Swiss Society for Microbiology (SSM) and Swiss Yeast Meeting: Emerging Microbes in a Changing World, 26-27 June 2013, Interlaken, Switzerland

Peer Reviewed