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New antimicrobials are urgently needed to combat the threat of multidrug-resistant bacteria worldwide. Our study aimed to access the antimicrobial and cytotoxic profiles of endophytic actinomycetes associated with Cinnamomum cassia Presl taken from a mountainous region in the Northwest of Vietnam. The antimicrobial activity, capability for anthracycline-like compounds production and presence of secondary metabolite-biosynthetic genes were consequently determined. Finally, the cytotoxicity of antibiotic-producing actinomycetes was carried out towards various cancer cell lines. A total of 81 actinomycetes were recovered from different organs (roots, stems, leaves) of Cinnamomum cassia, of which 20/81 isolates exhibited antimicrobial activities against at least one of nine microbial strains. The analysis of 16S rRNA genes indicated that antibiotic-producing isolates were grouped into 4 genera Streptomyces, Micromonospora, Saccharothrix, and Microbacterium, among which Streptomyces was the most prevalent. The presence of biosynthetic genes pks-I, pks-II or nrps was detected in 17/20 of isolates. Five strains of Streptomyces griseorubens LCQ8, Streptomyces variabilis LCQ43, Streptomyces californicus LCQ44, Streptomyces fragilis LCQ75, and Streptomyces beijiangensis LCQ77 exhibited broad-spectrum antimicrobial activity against various pathogens with the MIC values ranging from 16 to 256 µg/mL. Furthermore, characterized strains showed considerable cytotoxicity against MCF-7 cell lines with a 50% inhibition concentration of crude culture extracts of less than 30 µg/mL. The findings demonstrated that Streptomyces species isolated from Cinnamomum cassia in mountainous regions hold the potential for growth inhibition of human disease agents. [ABSTRACT FROM AUTHOR]

In order to screen endophytic bacteria resources with antitumor activities from medicinal plant, 300 endophytic actinomycetes isolated from Dracaena cochinchinensis collected from Xishuangbanna, China and Vietnam 'were studied. SRB method wras used to detect the activity of antitumor cells, agar diffusion and plate confrontation methods ■were used to test antimicrobial activities, Polymerase Chain Reaction wras used to detect NRPS, PKS-1 and PKS-D genes, and the taxonomic studies of the five selected active strains wrere performed using 16S rRNA gene analysis. Eight media wrere designed to cultivate five selected active strains and the antimicrobial activities of their fermented extraction ■were detected by oxford-cup test against ten pathogenic bacteria and three pathogenic fungi, the antitumor activities 'were measured by MIT assay in twro tumor cell lines. As a result, four of the five active strains wrere classified as Streptomyces spp. and the remaining one as Nocardioides sp. Different media resulted in different activities, most media of strain S04 sho\wed strong activities against eight pathogens and the inhibition rate of the fermentation product of S04 in Medium C on Hep G2 cell line 'was up to 100% , 'which could be a novel resource for the mining of bioactive compounds for further studies. [ABSTRACT FROM AUTHOR]

Bacteria associated with invertebrates are considered as good sources for biologically active compounds. Sponge-derived bacteria were screened for antimicrobial activities, the presence of the cluster genes of polyketide synthases (PKSs) and non-ribosomal peptide synthetases (NRPSs), and through a colony picking method. Crude extracts of broth cultures were tested for microbial inhibition. Eleven out of 25 isolated strains showed inhibition of at least one of eight tested indicator microorganisms. Antimicrobial activities were observed in the strains coded HM5, HM6, and HM9 with the presence of NRPS and PKSII genes, whereas the isolate HM21 held both NRPS and PKSII and inhibited only the growth of Bacillus subtilis by the well diffusion method and only inhibited Serratia marcescens by the colony picking method. Two isolates, HM5 and HM6, belonged to the species of Bacillus. Interestingly, the isolate HM9 was nearest to Streptomyces mexicanusT NBRC100915 (GenBank accession number AB249966) with 94% sequence similarity. This potent strain HM9 could possibly be considered as a new species and a good source for bioactive compound discovery. Some isolates showed NRPS/PKS genes but did not exhibit antimicrobial activity. Thus, we suggested that both molecular and traditional methods should be conducted for the screening of antimicrobial producers. [ABSTRACT FROM AUTHOR]