Bioprospecting Indoor Bacteria Producing Bioactive Metabolites.

New biomolecules are prospected for new antimicrobial, antiparasitic and cytostatic drugs. Here, we present bioassay-guided methods for prospecting indoor bacteria producing non-protein antibiotic molecules. Out of 650 bacterial colonies tested, 108 antimicrobial isolates representing 15 species and cryptic Actinobacteria, produced non-protein antibiotics affecting mammalian cells. Methanol extracts of the 108 strains tested with a battery of bioassays revealed four toxicity endpoints: (1) Cell death (CD). (2) Boar sperm motility inhibition (BSMI). (3) Inhibition of cell proliferation (ICP). (4) Mitochondrial toxicity (MT). The battery of endpoints divided the 108 strains into four toxicity profiles: Profile I: Lethal toxins (42 strains). Positive controls: Alamethicin, a channel forming ionophore and a biosurfactant surfactin. Profile II: Sublethal mitochondrial toxins (51 strains). Positive controls: The mitochondrial toxins valinomycin and antimycin A. Profile III: Sublethal cytostatic toxins (7 strains). Positive control: Chaetoglobosin A, a glucose transport inhibitor. Profile IV: Cytostatic toxins (8 strains). Positive controls: Actinomycin D, RNA syntesis inhibitor. Strains of Bacillus, Streptomyces and Paenibacillus produced amylosin, cereulide, surfactins, lichenysins, iturins, fengysin, valinomycin and fusarisidins. Strains of Peribacillus Lysinibacillus, Microbacterium, Nocardiopsis and cryptic Actnobacteria produced possible novel bioactive molecules. The indoor environments were easily accessible habitats for bacteria producing ionophores, surfactants, and mitochondrial toxins.