Fig. 3

a Phylogenetic analysis of Actinoalloteichus sp. AHMU CJ021. Numbers at the nodes represent bootstrap percentages obtained from 1000 replicates. The scale bar (0.005) represents nucleotide substitutions per site. Sequence alignment was performed with ClustalW. A phylogenetic tree was constructed with MEGA 7.0 software using neighbor-joining algorithm based on 16S rDNA gene sequences; b HPLC analyses of CRM A production (asterisk) in Actinoalloteichus sp. AHMU CJ021 wild type and mutant strains. (i) Actinoalloteichus sp. AHMU CJ021 wild type; (ii–iv) XC-11G, XC-11GU and XC-11GUR respectively; Transcriptional analysis, c RT-PCR assay and d qPCR assay, determined camE expression in the Actinoalloteichus sp. AHMU CJ021wild type strain (WT) and three mutants: XC-16R (M1), XC-14G (M2) and XC-11G (M3); e The bioassay comparison and screening of mutants generated by UV mutagenesis, the asterisk indicates the inhibition zone level of the original mutant XC-11G; the number of mutants belonging to each range is indicated up the column; f The cultured morphology of the Actinoalloteichus sp. AHMU CJ021 wild type strain and three mutants on M-ISP2 medium; g HPLC analyses for riboflavin (black solid circle) biosynthesis in the Actinoalloteichus sp. AHMU CJ021 wild type and mutant strains. (i) authentic standard of riboflavin; (ii) Actinoalloteichus sp. AHMU CJ021 wild type; (iii–v) XC-11G, XC-11GU and XC-11GUR, respectively