N&B results from Mrr mutant strains P_BAD-gfp::mrr^D203A and P_BAD-gfp::mrr^D203A + the pTrc99A-hhaII plasmid after pressure treatment or induction of the MTase HhaII. (A) Fluorescence intensity maps of GFP-Mrr^D203A (a) without treatment, (b) after 20 min at 100 MPa (HP) and (c) after induction of M.HhaII with IPTG for 60 min (20 × 20 μm). Maximum intensity scale is 2 counts per 40 μs pixel dwell-time. Bright-field images of P_BAD-gfp::mrr^D203A (d) without treatment, (e) after 20 min at 100 MPa (HP) and (f) after induction of M.HhaII with IPTG for 60 min. (B) Stoichiometry values of fluorescent proteins corresponding to GFP monomers (M), dimers (D), tetramers (T) or a possible equilibrium between dimer and tetramer (T-D) as deduced from the background corrected molecular brightness of fluorescent proteins in P_BAD-gfp-mrr (GFP), P_BAD-gfp::mrr^D203A without (D203A) or after pressure treatment (D203A +HP) and P_BAD-gfp::mrr^D203A + pTrc99A-hhall after induction of MTase expression (D203A +HhaII).