Fig. 1

Fluorescence of E. coli BL21(DE3) [pET21d(+)-gfpuv] bacterial colonies on solid media with various compositions. E. coli BL21(DE3) bacteria were transformed with the plasmid pET21d(+)-gfpuv and plated on Petri dishes with solid M9 minimal medium and 9 variants of LA solid medium containing different nitrogen sources. Cultures were grown overnight at 30 °C. A solid M9 minimal medium—this medium did not contain UV/blue-adsorbing organic content, so it was translucent to the transilluminator’s wavelength spectrum; B medium consisting of only yeast extract, NaCl and agar; C as in B with the addition of soya peptone; D tryptone peptone; E malt extract; F tryptose peptone; G gelatin peptone; H casein peptone; I proteose peptone; and J peptobak