Flow cytometric measurements were performed using a Partec CyFlow® Space (Sysmex Partec GmbH, Germany), which was equipped with a solid-state laser for excitation of green/yellow fluorescent proteins at 488 nm. Single cells were detected in forward and sideward scatter channels as well as in one fluorescent channel. A minimum of 40,000 cells were analyzed for the experiments.
To define the background fluorescence signal, non-labelled B. subtilis cultures were analyzed as control. Cultures used for measurements were grown for 5 h (if not indicated otherwise) in competence medium under the same conditions as described above (see section transformation frequency assay). For evaluation of the data, the FlowJo® software (FlowJo LLC, Ashland, USA) was used and a gate was set at 3 fluorescence units for all samples to isolate the fluorescent population and determine the percentage of fluorescent cells.
To define the background fluorescence signal, non-labelled B. subtilis cultures were analyzed as control. Cultures used for measurements were grown for 5 h (if not indicated otherwise) in competence medium under the same conditions as described above (see section transformation frequency assay). For evaluation of the data, the FlowJo® software (FlowJo LLC, Ashland, USA) was used and a gate was set at 3 fluorescence units for all samples to isolate the fluorescent population and determine the percentage of fluorescent cells.