Six cycloheptadepsipeptides, marformycins AeF (1e6), featuring a unique N-terminally formylated side chain and five non-proteinogenic amino acid residues, were isolated from the deep Sea-derived Streptomyces drozdowiczii SCSIO 10141. The previously unsolved absolute stereochemistry of 3 and 4 was determined and the structures of other four new congeners were elucidated by extensive spectroscopic, chiral-phase HPLC, and single-crystal X-ray diffraction analyses. Compounds 1e5 bear no cytotoxicity against a number of human tumor cell lines but show selective anti-infective activity against Micrococcus luteus.