Jm. Gasol et Pa. Del Giorgio, Using flow cytometry for counting natural planktonic bacteria and understanding the structure of planktonic bacterial communities, SCI MAR, 64(2), 2000, pp. 197-224
Flow cytometry is rapidly becoming a routine methodology in aquatic microbi
al ecology. The combination of simple to use bench-top flow cytometers and
highly fluorescent nucleic acid stains allows fast and easy determination o
f microbe abundance in the plankton of lakes and oceans. The different dyes
and protocols used to stain and count planktonic bacteria as well as the e
quipment in use are reviewed, with special attention to some of the problem
s encountered in daily routine practice such as Fixation, staining and abso
lute counting. One of the main advantages of flow cytometry over epifluores
cence microscopy is the ability to obtain cell-specific measurements in lar
ge numbers of cells with limited effort. We discuss how this characteristic
has been used for differentiating photosynthetic from non-photosynthetic p
rokaryotes, for measuring bacterial cell size and nucleic acid content, and
for estimating the relative activity and physiological state of each cell.
We also describe how some of the flow cytometrically obtained data can be
used to characterize the role of microbes on carbon cycling in the aquatic
environment and we prospect the likely avenues of progress in the study of
planktonic prokaryotes through the use of flow cytometry.