Fig. 3

Conversion of ectoine to 5-hydroxyectoine by EctD proteins from different microorganisms. a Overproduction of EctD proteins originating from V. salexigens, H. elongata, S. alaskensis, P. stutzeri, P. lautus, A. ehrlichii, and N. maritimus was performed in the E. coli strain FF4169, and total cellular extracts were analyzed on an 15 % SDS–polyacrylamide gel. b Production of EctD-Strep-tag II proteins from V. salexigens, H. elongata, S. alaskensis, P. stutzeri, P. lautus, A. ehrlichii, and N. maritimus was confirmed by Western blot analysis using a monoclonal antibody directed against the Strep-tag II affinity peptide (SA-WSHPQFEK) attached to the various EctD proteins [21, 22]. c The ectoine (grey) and 5-hydroxyectoine (red) content of the culture supernatants were assessed via HPLC analysis. Strain FF4169 harboring an ectD ⁺ plasmid was grown in MMA in shake flasks in the presence of ampicillin and 0.4 M NaCl that had been supplemented by the addition of 10 mM ectoine. The values given for the ectoine and 5-hydroxyectoine content are the means and standard deviations of two independently grown cultures