Fig. 4

Final OD600 of strains after a 21-h expression at 37 °C with 1.5% w/v xylose supplemented for recombinant gene induction in LB and M9 media. The M9 minimal media was supplemented with 1% w/v glucose as a carbon and energy source. Strains with an asterisk (*) were unable to grow overnight in M9 media when cultures were inoculated from a single colony, these strains were also observed to have an extended lag when expression cultures in M9 minimal media were inoculated from overnight cultures grown in LB media. Additional expressions were performed with strain Yngk in altered M9 minimal media that contained 0.3 g/L of glutamate (+ 1aa), 0.3 g/L of histidine, isoleucine, phenylalanine, proline, tyrosine, lysine, and methionine (+ 7aa), 0.3 g/L of glutamate, histidine, isoleucine, phenylalanine, proline, tyrosine, lysine, and methionine (+ 8aa), 10 mM sodium acetate at time of induction (+ 10 mM), 30 mM sodium acetate at time of induction (+ 30 mM), and 90 mM sodium acetate at time of induction (+ 90 mM). Wild type corresponds to the B. megaterium MS941 strain lacking a silk expression vector. Error bars represent standard deviations from the mean values of three replicates