7‐Siderophore Classification (latest)
Within each cluster, there are common features of functional groups or biosynthetic types.
Cluster 1 (235, 33.24%) includes siderophores with phenyl ring structures in the functional groups such as catecholate, phenolate, hydroxyphenyloxazoline, and hydroxyphenylthiazoline. Siderophores in the cluster 1 are synthesized by both NRPS and NIS.
Cluster 2 (210, 29.70%) only includes siderophores produced by NRPS pathways except Albomycins by the hybrid NRPS/NIS pathway. Albomycins are naturally occurring sideromycins (siderophore–antibiotic conjugates) produced by some streptomycetes, and their siderophore parts are synthesized by NRPS.
From the perspective of functional groups, most siderophores in the cluster 2 contain hydroxamate of (92.86%, 195/210), and many also contain alpha-hydroxycarboxylate (40.48%, 85/210).
Cluster 3 (115, 16.27%) is all NIS siderophores. Like cluster 1, most of them contain hydroxamate (92.17%, 106/115), and many also contain alpha-hydroxycarboxylate (28.70%, 33/115). The sources of alpha-hydroxycarboxylate are mostly citrate.
Cluster 4 (80, 11.32%) is NRPS siderophores with chromophores such as pyoverdines (93.75%, 75/80). Other small clusters all are located on the edge of four large clusters.