Characterization and biological screening of the culturable endophytic actinomycetes from Garcinia cowa Roxb.

Actinomycetes associated with plants are relatively interactive sources of potential natural products. Two culturable endophytic actinomycetes strains, GcL-T1-1 and GcLT2-2, were isolated from a leaf of cowa (Garcinia cowa Roxb.). Determination of morphological and physiological properties, strains GcL-T1-1 and GcLT2-2, formed filament cells and presented spores on the mycelia which were classified to actinomycete group. In addition, strain GcL-T1-1 belonged to Streptomyces based on morphological and chemotaxonomic characteristics, which contained LL- diaminopimelic acid in peptidoglycan of cell wall. The molecular identification using similarity value of 16S rRNA gene, a non-streptomycete GcL-T2-2 was classified within the family Micromonosporaceae, genus Micromonospora that presented the highest similarity with M. schwarzwaldensis HKI0641T (99.93%), follow with M. haikouensis 232617T (99.23%), M. humi DSM 45647T (99.16%), M. maritima D10-9-5T (99.16%), M. sediminicola DSM 45794T (99.16%), M. oryzae CP2R9-1T (99.16%) and M. mangrove 2803GPT1-18T (99.16%). In addition, neighbour-joining phylogeny confirmed that strain GcL-T2-2 formed a phyletic line within Micromonospora. Biological screening for antimicrobial and cytotoxic activities, ethyl acetate crude extract of Micromonospora sp. GcL-T2-2 exhibited activity against Bacillus cereus and NCI-H187 tumor cells at MIC of 50 µg/mL and IC50 of 48.12 µg/mL, respectively. The Garcinia cowa associated Streptomyces strain GcLT1-1 exhibited cytotoxic activity with NCI-H187 tumor cells at the IC50 value of 43.20 µg/mL. However, antagonistic activity against Alternaria brassicicola and Colletotrichum acutatum was an inactive result that displayed MIC value of more than 50 µg/mL.