These 19 genes share greater than 92% sequence identity at the protein level. Table 2 Protein names, putative function, and % identity of the encoded Hpi, Amb and Wel enzymes Enzyme FS ATCC 43239 FS PCC 9339 FA UTEX 1903 HW IC-52-3 WI HT-29-1 FS PCC 9431 FM SAG 1427-1 % identity* Tryptophan biosynthesis:                 TrpE HpiT1

HpiT1 AmbT1 WelT1 WelT1 WelT1 WelT1 93.3 TrpC HpiT2 HpiT2 AmbT2 WelT2 WelT2 WelT2 WelT2 92 TrpA HpiT3 HpiT3 AmbT3 WelT3 WelT3 WelT3 WelT3 MI-503 92.7 TrpB HpiT4 HpiT4 AmbT4 WelT4 WelT4 WelT4 WelT4 95.7 TrpD HpiT5 HpiT5 AmbT5 WelT5 WelT5 WelT5 WelT5 94.8 DAHP synthase HpiC2 HpiC2 AmbC2 WelC2 WelC2 WelC2 WelC2 95.3 IPP and DMAPP biosynthesis:                 Dxr HpiD1 HpiD1 AmbD1 WelD1 WelD1 WelD1 WelD1 96.4 Dxs HpiD2 HpiD2 AmbD2 WelD2 WelD2 WelD2 WelD2 97.7 IspG HpiD3 HpiD3 AmbD3 WelD3 WelD3 WelD3 WelD3 98.7 IspH HpiD4 HpiD4 AmbD4 WelD4 WelD4 WelD4 – 95.3 Isonitrile biosynthesis:                 IsnA HpiI1 HpiI1 AmbI1

WelI1 WelI1 WelI1 WelI1 94 IsnA HpiI2 HpiI2 AmbI2 WelI2 WelI2 WelI2 WelI2 96.2 IsnB HpiI3 HpiI3 AmbI3 WelI3 WelI3 WelI3 WelI3 95.6 Prenyltransferases:                 Aromatic prenyltransferase HpiP1 HpiP1 AmbP1 WelP1 WelP1 WelP1 WelP1 96.9 GPP HpiP2 HpiP2 AmbP2 WelP2 WelP2 WelP2 – 93 Aromatic prenyltransferase – - AmbP3 – - – - – Methyltransferases:                 N-methyltransferase – - – WelM1 WelM1 WelM1 – 98.8 SAM-dependent check details methyltransferase – - – WelM2 WelM2 WelM2 WelM2 91.2 Histamine N-methyltransferase – - – WelM3 WelM3 WelM3 – 99 Regulation proteins                 Response regulator containing a CheY-like receiver domain and an HTH DNA-binding domain HpiR1 HpiR1 AmbR1 WelR1 WelR1 WelR1 – 93.4 Transcriptional regulator, LuxR family HpiR2 HpiR2 AmbR2 WelR2 WelR2 WelR2 – 96.2 Response regulator those with CheY-like receiver domain and winged-helix DNA-binding domain – - – WelR3 WelR3 WelR3 WelR3 93.3 Other:                 Dephospho-CoA kinase-like protein HpiC1 HpiC1 AmbC1

WelC1 WelC1 WelC1 WelC1 93.2 Phosphoglycerate mutase family protein HpiC3 HpiC3 AmbC3 WelC3 WelC3 WelC3 WelC3 96.4 Transporter genes:                 DevC protein – HpiE1 AmbE1 – - – - 98.2 ABC exporter membrane fusion protein, DevB family – HpiE2 AmbE2 – - – - 99.7 Conserved membrane hypothetical protein – HpiE3 AmbE3 – - – - 100 Small multidrug resistance protein – - – WelE4 WelE4 WelE4 – 97.8 *The % identity is based on comparison of all enzymes sequenced. Organization of genes Comparison of the gene organization of the hpi/amb/wel gene clusters identified groups of genes whose order and orientation are conserved, however, the presence/absence of specific genes distinguish the hpi, amb and wel gene clusters from each other (Figure 2).