*2.2. CYP110 is the Dominant P450 Family in Cyanobacterial Species*

As per the International P450 Nomenclature Committee rules [60–62], 341 P450s found in 88 cyanobacterial species can be grouped into 36 P450 families and 79 P450 subfamilies (Figure 4 and Table S3). Phylogenetic analysis of cyanobacterial species P450s revealed grouping of P450s belonging to the same family together on the tree (Figure 2), indicating the correct assignment of P450 families and subfamilies. Among 36 P450 families, CYP110 has the highest number of P450s (176 P450s), followed by CYP120 (59 P450s), CYP213 (16 P450s) and P450 families, CYP197 and CYP284, which have 11 P450s in each (Figure 4). Comparative analysis of P450 families among different bacterial species revealed that different bacterial species have different dominant P450 families (Table 1). CYP110 is the dominant P450 family in cyanobacterial species, whereas CYP125 is dominant in mycobacterial species and CYP107 in *Bacillus* species and *Streptomyces* species (Table 2). The molecular basis for the blooming (P450 family with many members) [63] of certain P450 families is attributed to the species habitat and lifestyle [55]. In addition to this, P450 subfamily-level blooming was observed in cyanobacterial species, where some subfamilies were found to be dominant in a particular family (Table S3). For example, among 26 subfamilies found in the CYP110 family, subfamilies C (34 P450s), E (29 P450s), D (26 P450s) and A (15 P450s) are dominant; among six subfamilies found in CYP120 family, subfamilies A (35 P450s) and B (16 P450s) are dominant (Table S3), indicating the subfamily-level blooming of P450s in cyanobacterial species.

**Figure 4.** Family level comparative analysis of P450s in the species of *Cyanobacteria*. The numbers next to the family bar indicate the number of P450s. The data on the number of P450 families, along with subfamilies, are presented in Supplementary Table S3.

Apart from five P450 families, the remaining 31 P450 families in cyanobacterial species have a single-digit number of members (Figure 4). In fact, 17 P450 families have a single P450, indicating high P450 family diversity in cyanobacterial species. This was further confirmed when the P450 diversity percentage was compared among different bacterial species (Table 2). The P450 diversity percentage in cyanobacterial species was found to be highest compared to *Bacillus* species and mycobacterial species and almost 50% lower compared to *Streptomyces* species (Table 2). The highest P450 diversity observed for cyanobacterial species indicates that these P450s might have diverse roles, as was observed for *Streptomyces* species [55]. However, future functional analysis of cyanobacterial species P450s will provide more evidence on this observation.

P450 family conservation analysis revealed that none of the 36 families were conserved in 88 cyanobacterial species (Figure 5). The P450 profile heat-map revealed that the P450 families CYP110 and CYP120 were found to be a co-presence in most of the cyanobacterial species (Figure 5). Non-conservation of P450 families was also observed in *Bacillus* species [54], but in the *Streptomyces* [55] and mycobacterial species [59] quite a large number of P450 families were found to be conserved.

**Figure 5.** Heat-map of the presence/absence of P450 families in 88 cyanobacterial species. The data is represented as 3 for family presence (**red**) and –3 for family absence (**green**). Eighty-nine cyanobacterial species form the horizontal axis and P450 family numbers form the vertical axis. A detailed table showing P450 family profiles in each of the cyanobacterial species is presented in Supplementary Dataset 3.
