Figure 3

The pmrH-gfp fusion is expressed in flow chamber biofilms under repressive high Mg²⁺conditions. Biofilms of strain 14028 expressing a plasmid-encoded pmrH-gfp construct were cultivated for 2 days in NM2 (pH 7.4) under inducing conditions with 0.1 mM Mg²⁺ (A-D) or under inducing conditions with 0.1 mM Mg²⁺ for 28 hours followed by the injection of excess 10 mM Mg²⁺ into the flow chambers for an additional 16 hours (E-H). Gfp fluorescence was monitored in A,E; extracellular DNA was stained in B,F (pseudocoloured yellow); EPS was stained in C,G (pseudocoloured purple); and the merged image of the three channels is shown in D,H. The scale bar equals 20 μM.