This includes Tables A-E and Figures A-E.

Table A. Group setup of the experiment in this study. Table B. Richness and diversity indices of the original AS and three groups. Table C. Significance tests of the differences of the microbial communities. Table D. Correlations between the relative abundance of microbial community compositions and indigo yields. Table E. Correlations between the relative abundance of the major unclassified OTU and indigo yields. Fig A. Color of the products produced by the three groups. The reaction mixture were centrifuged at 10,000×g for 5 min, and the pellets were re-suspended in an equal volume of dimethylsulfoxide for the extraction of indigoid pigments. Fig B. HPLC-MS analysis of the products formed by the three groups. a. HPLC spectra of the products. b. Mass spectra of the product indigo. c. Mass spectra of the purple product. The pigments of I and II were indicated by the arrows, corresponding to indigo and purple product, 2-(7-oxo-1H-indol-6(7H)-ylidene) indolin-3-one, respectively. Fig C. Proposed pathways for the production of indigoids from indole by the activated sludge systems. Indole can be hydroxylated to form indoxyl by oxygenases A and B, which may be further oxidized to form isatin. Condensation of two molecules of indoxyl by air oxidation will lead to the production of indigo. Besides, indole can be also oxidized by oxygenase B to form 7-hydroxyindole, which can react with isatin to form 2-(7-oxo-1H-indol-6(7H)-ylidene) indolin-3-one. Oxygenase A may be naphthalene dioxygenase in G1; B may be phenol hydrolase in G2 or other oxygeases in G3. Fig D. Rarefaction curves base on Illumina MiSeq sequencing of microbial communities. The OTUs were defined by 3% distances. The rarefaction curve of AS was derived from 3 samples, while those of each group were from 11 samples. The detailed group setup was presented in Table A in S1 File. Fig E. Relative abundance of Proteobacteria subdivisions in each group at different stages.
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