Abstract
Streptomycetes have been the center of attraction within scientific community owing to their capability to produce various bioactive compounds, for instance, with different antimicrobial, anticancer, and antioxidant properties. The search for novel Streptomyces spp. from underexplored area such as mangrove environment has been gaining attention since these microorganisms could produce pharmaceutically important metabolites. The aim of this study is to discover the diversity of Streptomyces spp. from mangrove in Sarawak and their bioactive potentials — in relation to antioxidant and cytotoxic activities. A total of 88 Streptomyces isolates were successfully recovered from the mangrove soil in Kuching, state of Sarawak, Malaysia. Phylogenetic analysis of all the isolates and their closely related type strains using 16S rRNA gene sequences resulted in 7 major clades in the phylogenetic tree reconstructed based on neighbour-joining algorithm. Of the 88 isolates, 18 isolates could be considered as potentially novel species according to the 16S rRNA gene sequence and phylogenetic analyses. Preliminary bioactivity screening conducted on the potential novel Streptomyces isolates revealed significant antioxidant activity and notable cytotoxic effect against tested colon cancer cell lines (HCT-116, HT-29, Caco-2, and SW480), with greater cytotoxicity towards SW480 and HT-29 cells. This study highlighted that the Sarawak mangrove environment is a rich reservoir containing streptomycetes that could produce novel secondary metabolites with antioxidant and cytotoxic activities.
Highlights
The remarkable contribution of microbes towards the area of drug discovery has improved human welfare around the world[1]
The isolation media were supplemented with cycloheximide to suppress the growth of fungi and nalidixic acid to suppress the growth of Gramnegative bacteria[54,55]
The present study examined the cytotoxic potential of extracts in four high-throughput models against human colon cancer cell lines: HCT-116, HT-29, Caco-2, and SW480, with extracts examined at 400 μg/mL
Summary
The remarkable contribution of microbes towards the area of drug discovery has improved human welfare around the world[1]. This is due to their capability in producing various useful natural products which later became the source of countless active ingredients of medicines[2,3,4] In this regard, bacteria belonging to the genus Streptomyces have been acknowledged as the producers of many bioactive compounds, which makes them to be important microorganisms for drug discovery[5,6]. These unusual environmental changes may be the driving force for the development of microbial species diversity and adaptation of metabolic pathways that could be responsible to generate certain unique properties of microorganisms[19,26] In this context, the study of streptomycetes from mangrove may provide a better prospect of uncovering novel Streptomyces spp. which may subsequently bring about the discovery of valuable bioactive molecules[27,28]. The genus Streptomyces is a good source of chemotherapeutic agents verified through the discovery of several clinically important anticancer medicines such as mitomycin C45, dactinomycin[46], doxorubicin (synonym adriamycin)[47], and bleomycin[13,48,49]
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