FIG 3 .

Growth of the derivatives of E. coli strain BM4062 carrying plasmid pBAD322 (empty vector) or pBAD322 derivatives encoding either the F. novicida BplA or BirA ligase. (A) Ligase expression was induced with arabinose; the strain BM4062 derivative with a wild-type arabinose operon was used to avoid arabinose toxicity. The biotin concentrations are shown below each plate. As shown at the higher biotin concentrations in the sectors containing the vector strain, the BirA encoded by the host strain mutant has weak ligase activity (21). (B) The strains were grown in the absence of arabinose induction and in the presence of glucose to repress the basal level of expression from the paraBAD promoter. The original strain BM4062 was used. Strain BM4062 containing the plasmid encoding BplA was streaked in the left-hand sectors, whereas the right-hand sectors contained the BirA-encoding plasmid. The plates were minimal medium M9 supplemented with 0.1% Casamino Acids, 40 µg/ml X-Gal, and 100 µg/ml ampicillin with 0.2% arabinose supplementation (A) and 0.4% glucose supplementation (B). The plates were incubated overnight at either 42°C (A) or 37°C (B).