The lichen-derived Streptomyces isolated from Pyxine cocoes produces the antibiotic with potent antimicrobial and antitumor activities

The actinobacteria strain Lp03 was isolated from the lichen, Pyxine cocoes, collected from Lumpini Park, Bangkok, Thailand. Based on the polyphasic approach, strain Lp03 was identified as Streptomyces parvulus. Actinomycin D produced by this strain exhibited antibacterial activity against Bacillus cereus (MIC 1.56 pg/ml), Bacillus subtilis (MIC 5 pg/ml), Escherichia coli (MIC 12.5 pg/ml), Kocuria rhizophila (MIC 0.076 ng/ml), Klebsiella pneumoniae (MIC 0.78 pg/ml), Staphylococcus aureus (MIC 9.76 ng/ml), Staphylococcus epidermidis (MIC 9.76 ng/ml), and Mycobacterium tuberculosis (MIC 12.5 pg/ml). Actinomycin D was inactive against Acinetobacter baumannii, but the new finding revealed that it showed activity against A. baumannii when combined with beta-naphthylamide (PN beta N), the efflux inhibitor. Antiparasitic activity was observed against Plasmodium falciparum with an IC50 value of 14.8 ng/ml. It showed cytotoxicity against Vero cells, NCI-H187, KB, and MCF-7 with IC50 values of 125, 0.694, 18.4 ng/ml, and 21.94 pg/ml, respectively. The genome of S. parvulus harbors a high diversity of biosynthetic gene clusters for secondary metabolites (BGCs). The actinomycin BGCs could be detected in all publicly available genomes of S. parvulus but could be varied among the strains. This study is the first record for the complete taxonomic study and bioactive compound produced by S. parvulus isolated from the lichen.