Fe−N−C catalysts for the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs) are still inferior to the Pt catalysts. The major downsides of Fe−N−C are the low density and ambiguous structural identification of active sites. Fe−N−C single‐atom catalysts (SACs) have shown great potential for maximizing the active site density and can serve as ideal platforms for investigating the nature of active sites. This review starts with a summary of the latest progress in the synthetic strategy for Fe−N−C SACs, followed by an introduction to the active site identification by atomic‐resolution techniques and electrochemical analyses. Finally, the major challenges are highlighted, and the prospective directions are proposed to guide the development of high‐performance Fe−N−C catalysts.

Bioactive secondary metabolites from Streptomycetes are important sources of lead compounds in current drug development. Streptomyces costaricanus SCSIO ZS0073, a mangrove-derived actinomycete, produces actinomycin D, a clinically used therapeutic for Wilm’s tumor of the kidney, trophoblastic tumors and rhabdomyosarcoma. In this work, we identified the actinomycin biosynthetic gene cluster (BGC) acn by detailed analyses of the S. costaricanus SCSIO ZS0073 genome. This organism produces actinomycin D with a titer of ~69.8 μg mL−1 along with traces of actinomycin Xoβ. The acn cluster localized to a 39.8 kb length region consisting of 25 open reading frames (ORFs), including a set of four genes that drive the construction of the 4-methyl-3-hydroxy-anthranilic acid (4-MHA) precursor and three non-ribosomal peptide synthetases (NRPSs) that generate the 4-MHA pentapeptide semi-lactone, which, upon dimerization, affords final actinomycin D. Furthermore, the acn cluster contains four positive regulatory genes acnWU4RO, which were identified by in vivo gene inactivation studies. Our data provide insights into the genetic characteristics of this new mangrove-derived actinomycin D bioproducer, enabling future metabolic engineering campaigns to improve both titers and the structural diversities possible for actinomycin D and related analogues.