A representative example of PKS-I gene cluster (#46 in Figure 2) (A), and its putative product (B). The cluster is specific to N. asteroides NBRC 15531T. A. Domain organization. LM, loading module; m1 – m11, modules; KS, ketosynthase; AT, acyltransferase; ACP, acyl carrier protein; DH, dehydratase; KR, ketoreductase; ER, enoyl-reductase domains. Gray ’DH” domains are probably inactive. B. Chemical structure of intermediate polyketide chain predicted from the gene cluster #46 based on assembly line rule [46, 49].