Oct 9, 2002 - hybridization, demonstrated that cAMP was taken up by 18% of all cells. The bacterial .... plied Biosystems, Foster City, Calif.) as specified by ...
Effect of Signal Compounds and Incubation Conditions on the Culturability of Freshwater Bacterioplankton Alke Bruns,1 Ulrich Nu ¨bel,2 Heribert Cypionka,1 and Jo ¨rg Overmann1* Institut fu ¨r Chemie und Biologie des Meeres, Carl von Ossietzky Universita ¨t Oldenburg, D-26111 Oldenburg,1 and Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH, D-38124 Braunschweig,2 Germany Received 9 October 2002/Accepted 7 January 2003
The effect of signal compounds and of different incubation conditions on the culturability (i.e., the fraction of all cells capable of growth) of natural bacterioplankton from the eutrophic lake Zwischenahner Meer was investigated over a period of 20 months. Numbers of growing cells were determined by the most-probablenumber technique in liquid media containing low concentrations (10 M) of the signal compounds N(oxohexanoyl)-DL-homoserine lactone, N-(butyryl)-DL-homoserine lactone, cyclic AMP (cAMP), or ATP. cAMP was the most effective signal compound, leading to significantly increased cultivation efficiencies of up to 10% of the total bacterial counts. Microautoradiography with [2,8-3H]cAMP, combined with fluorescence in situ hybridization, demonstrated that cAMP was taken up by 18% of all cells. The bacterial cAMP uptake systems had a very low Km value of
