Fig. 2

Biosynthesis of indole compounds in the presence and absence of tryptophan (Trp). An aliquot of the S. marcescens UENF-22GI inoculum was transferred to Dygs medium with or without tryptophan (100 mg∙L^− 1) and incubated for 72 h in the dark, at 30 °C and 150 rpm. To evaluate indole synthesis, 150 μL of grown bacteria were transferred to microplates and 100 μL of Salkowski reagent (see methods for details) were added. The plate was incubated for 30 min in the dark and samples analyzed at 492 nm on a spectrophotometer