Current and future applications of flow cytometry in aquatic microbiology

Flow cytometry has become a valuable tool in aquatic and environmental micr obiology that combines direct and rapid assays to determine numbers, cell s ize distribution and additional biochemical and physiological characteristi cs of individual cells, revealing the heterogeneity present in a Copulation or community. Flow cytometry exhibits three unique technical properties of high potential to study the microbiology of aquatic systems: (i) its treme ndous velocity to obtain and process data; (ii) the sorting capacity of som e cytometers, which allows the transfer of specific populations or even sin gle cells to a determined location, thus allowing further physical, chemica l, biological or molecular analysis; and (iii) high-speed multiparametric d ata acquisition and multivariate data analysis. Flow cytometry is now commo nly used in aquatic microbiology, although the application of cell sorting to microbial ecology and quantification of heterotrophic nanoflagellates an d viruses is still under development. The recent development of laser scann ing cytometry also provides a new way to further analyse sorted cells or ce lls recovered on filter membranes or slides. The main infrastructure limita tions of flow cytometry are: cost, need fur skilled and well-trained operat ors, and adequate refrigeration systems for high-powered lasers and cell so rters. The selection and obtaining of the optimal fluoruchromes. control mi croorganisms and validations for a specific application may sometimes be di fficult to accomplish. (C) 2000 Federation of European Microbiological Soci eties. published by Elsevier Science B.V. All rights reserved.