Fig. 2

Representative histidine decarboxylase gene clusters for putative histamine-secreting bacteria. Two types of bacterial histidine decarboxylases were labeled as hdcA pyruvoyl and hdcA PLP respectively. Two arginine decarboxylases were identified in some histidine decarboxylase species including aaxB and adiA. Three different types of amino acid antiporters in histidine decarboxylase clusters (hdcP) were labelled as gadC, aaxC and adiC. The phylogenetic tree was a subtree extracted from a pre-built GTDB phylogenomic tree based on 120 bacterial marker genes. Gene clusters along with the tree were visualized by ggtree (version 2.5.1) [43]. The break symbol (double slash mark) was placed between two distant histidine decarboxylase gene clusters for species Plesiomonas shigelloides