Caulobacter crescentus CB15N (8 (link)) and its derivatives were grown in PYE rich or M2G minimal medium (6 (link)) at 28°C. For cloning purposes, plasmids were propagated in Escherichia coli TOP10 (Invitrogen), which was cultivated in Luria-Bertani medium at 37°C. When appropriate, media were supplemented with antibiotics at the following concentrations (liquid/solid media for C. crescentus; liquid/solid media for E. coli; in μg/ml): spectinomycin (25/50; 50/100), kanamycin (5/25; 30/50), rifampicin (2.5/5; 25/50), gentamicin (0.5/5; 15/20), oxytetracycline (1/1; 12/12), chloramphenicol (2/1; 20/30), apramycin (10/60; 30/30). Plasmid transfer into C. crescentus was achieved by electroporation (6 (link)). Escherichia coli was transformed using a chemical method (9 (link)). The CB15N derivatives MT219 (▵vanR) and MT231 (▵vanA) were generated with the help of plasmids pMT422 and pMT487, respectively, following a previously described gene replacement protocol (10 (link)). Strains MT232, MT236 and MT240 were created by transforming strain CB15N with integration plasmids pMT627, pMT704 or pMT760, respectively, and selecting for homologous recombination of the constructs into the chromosomal vanA or xylX locus.