Flow cytometry of bacteria: glimpses from the past with a view to the future

Measurement of bacteria and other microorganisms at the level of single cel ls has progressed enormously over the last couple of decades. Up to the lat e 1970s, there were no other means than microscopy for observation of singl e microorganisms, making any type of measurement very cumbersome and tediou s, at best. Today, we measure several parameters simultaneously with a prec ision of a few per cent, and at a rate of 1000 cells per second. The first papers on the use of how cytometry to measure bacteria appeared only in 197 7, although the method had proved highly successful in studies of mammalian cells for almost a decade. There were several reasons for this relatively late introduction, including technical limitations, problems with adequate staining, and, not least, the human factor. Today, flow cytometry has a wid e range of microbiological applications, ranging from studies of the bacter ial cell cycle and many other cellular characteristics to assessment of ant ibiotic susceptibility of clinical samples, and monitoring of bacteria and other microorganisms in anything from sewage to sea water. Still, the poten tial of flow cytometry in microbiology is far from fully utilised. Better i nstruments and new stains will provide new opportunities to understand, con trol and exploit this vital part of the biosphere. (C) 2000 Elsevier Scienc e B.V. All rights reserved.