Strain 12A35 was isolated from a deep-sea sediment collected from the South China Sea and showed promising antibacterial activities. It was identified as Streptomyces sp. by the 16S rDNA sequence analysis. Bioassay-guided fractionation using HP20 adsorption, flash chromatography over silica gel and octadecylsilyl (ODS) and semi-preparative HPLC, led to the isolation and purification of five metabolites from the fermentation culture of 12A35. Two new spirotetronate antibiotics, lobophorins H (1) and I (2), along with three known analogues, O-β-kijanosyl-(1→17)-kijanolide (3), lobophorins B (4) and F (5) were characterized by 1D, 2D-NMR and MS data. These compounds exhibited significant inhibitory activities against Bacillus subtilis. Compounds 1 and 5 exhibited moderate activities against Staphylococcus aureus. In particular, the new compound lobophorin H (1) showed similar antibacterial activities against B. subtilis CMCC63501 to ampicillin.

Extracellular alkalinization and H₂O₂ production are important early events during induced resistance establishment in plants. In a screen for metabolites as plant resistance activators from 98 fungal isolates associated with marine sponge Hymeniacidon perleve, the cyclopiazonic acids (CPAs) produced by Aspergillus oryzae HMP-F28 induced significant extracellular alkalinization coupled with augmented H₂O₂ production in tobacco cell suspensions. Bioassay-guided fractionation led to the isolation and structural elucidation of a new CPA congener (4, 3-hydroxysperadine A) and three known ones (1–3). To construct a mutasynthetic strain to generate unnatural CPA analogues, a hybrid pks-nrps gene (cpaS) was disrupted to abolish the production of the critical precursor of cyclo-acetoacetyl-L-tryptophan (cAATrp) and all the downstream CPA products. Elimination of cAATrp will allow cAATrp mimics being processed by the CPA biosynthetic machinery to produce CPA derivatives with designed structural features. Screening, characterization and abolishment of the cyclopiazonic acids produced by a sponge-associated fungus Aspergillus oryzae HMP-F28