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Aquatic Microbial Ecology

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AME 33:41-51 (2003)  -  doi:10.3354/ame033041

Activity and diversity of bacterial cells with high and low nucleic acid content

Pierre Servais1, Emilio O. Casamayor2,3, Claude Courties2, Philippe Catala2, Nathalie Parthuisot2, Philippe Lebaron2,*

1Ecologie des Systèmes Aquatiques, Université Libre de Bruxelles, Campus Plaine, CP 221, 1050 Bruxelles, Belgium
2Observatoire Océanologique, Laboratoire ARAGO, Université Pierre et Marie Curie, UMR 7621-7628 CNRS-INSU, BP 44, 66651 Banyuls-sur-Mer cedex, France
3Present address: Unitat de Limnologia, Centre d¹Estudis Avançats de Blanes (CSIC), Accés Cala Sant Francesc 14, 17300 Blanes, Spain
*Corresponding author. Email:

ABSTRACT: In most aquatic environments, at least 2 subpopulations of bacterial cells can be discriminated by flow cytometry based on their nucleic acid content. Recent investigations have shown that the cells with a high nucleic acid (HNA) content have a higher cell-specific activity (CSA) cell than those with a low nucleic acid (LNA) content. In this study, the CSA and biomass-specific activities (BSA) of HNA and LNA cells from different aquatic ecosystems, including marine, brackish and freshwater, were investigated using radioactive leucine incorporation and cell sorting by flow cytometry. The genetic diversity of natural assemblages, HNA and LNA cells was investigated using the SSCP (PCR single-strand conformation polymorphism) method. Data showed that both CSA and BSA of HNA cells were always significantly higher than CSA and BSA of LNA cells. In addition, HNA cells had a dominant contribution to the production of the total community (77 to 98%). For the different samples, the SSCP fingerprints from the natural assemblage and from the 2 sorted fractions were not significantly different. This clearly suggests that HNA and LNA subpopulations were composed by the same dominant species and, thus, confirms an important heterogeneity of physiological states within most natural populations.

KEY WORDS: Nucleic acid content · Side scatter · Cellular activity · Flow cytometry · Cell sorting · Genetic diversity · Single-strand conformation polymorphism

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