Figures & data
Figure 1. Bioassay for biotin quantification. (A) The E. coli ΔbioH ΔyigM strain and its parent (E. coli ΔbioH) were grown in mineral salts medium supplemented with biotin, harvested, washed and starved for biotin as described.Citation19 The starved cells (200 μl at OD600 = 1) were mixed with 5 ml of melted mineral salts soft agar (0.7% w/v agar), and the mixtures were poured onto mineral salts agar plates. Biotin solutions with the indicated concentrations were loaded on paper disks (10 μl for the ΔbioH ΔyigM strain, 5 μl for the ΔbioH strain), the disks were placed on the agar plates, and the plates were incubated for approx. twenty-four h at 37 °C. Diffusion of biotin into the agar allows growth of the biotin-deficient reporter strains around the disks resulting in a halo. (B) Correlation of halo sizes with biotin concentrations. Halo sizes of three independent assays were measured. The values represent the means of triplicate determinations ± the standard deviation. Sensitivity and detectable concentration are in a similar range as recently reported for a bioassay based on Corynebacterium glutamicum strains.Citation30
