Indonesia is one of the most biodiverse countries in the world and a promising resource for novel natural compound producers. Actinomycetes produce about two thirds of all clinically used antibiotics. Thus, exploiting Indonesia’s microbial diversity for actinomycetes may lead to the discovery of novel antibiotics. A total of 422 actinomycete strains were isolated from three different unique areas in Indonesia and tested for their antimicrobial activity. Nine potent bioactive strains were prioritized for further drug screening approaches. The nine strains were cultivated in different solid and liquid media, and a combination of genome mining analysis and mass spectrometry (MS)-based molecular networking was employed to identify potential novel compounds. By correlating secondary metabolite gene cluster data with MS-based molecular networking results, we identified several gene cluster-encoded biosynthetic products from the nine strains, including naphthyridinomycin, amicetin, echinomycin, tirandamycin, antimycin, and desferrioxamine B. Moreover, 16 putative ion clusters and numerous gene clusters were detected that could not be associated with any known compound, indicating that the strains can produce novel secondary metabolites. Our results demonstrate that sampling of actinomycetes from unique and biodiversity-rich habitats, such as Indonesia, along with a combination of gene cluster networking and molecular networking approaches, accelerates natural product identification.

A novel endo-β-1,4-mannanase gene was cloned from a novel actinomycetes, Nonomuraea jabiensis ID06-379, isolated from soil, overexpressed as an extracellular protein (47.8 kDa) in Streptomyces lividans 1326. This new endo-1,4-β-mannanase gene (manNj6-379) is encoded by 445-amino acids. The ManNj6-379 consists of a 28-residue signal peptide and a carbohydrate-binding module of family 2 belonging to the glycoside hydrolase (GH) family 5, with 59–77% identity to GH5 mannan endo-1,4-β-mannanase. The recombinant ManNj6-379 displayed an optimal pH of 6.5 with pH stability ranging between 5.5 and 7.0 and was stable for 120 min at 50 °C and lower temperatures. The optimal temperature for activity was 70 °C. An enzymatic hydrolysis assay revealed that ManNj6-379 could hydrolyze commercial β-mannan and biomass containing mannan.

Setiawati S, Nuryastuti T, Sholikhak EN, Lisdiyanti P, Pratiwi SUT, Sulistiyanti TR, Ratnakomala S, Jumina, Mustofa. 2021. The potency of actinomycetes extracts isolated from Pramuka Island, Jakarta, Indonesia as antimicrobial agents. Biodiversitas 22: 1104-1111. Actinomycetes are one of the Gram-positive bacteria which are widely distributed and produce many secondary metabolites including those known as antibiotics, antifungals, anticancer, and antimalarials agents. The secondary metabolites of actinomycetes are abundant, which include many active compounds that have been identified because of the large diversity in the actinomycetes phylum. This study aimed to identify and screen collected by Indonesian Culture Collection (InaCC) from Bojong Gede and Pramuka Island, Jakarta, Indonesia as antibacterial and antifungal agents. Primary screening was done on 16 actinomycetes isolates by well-agar diffusion method. Antimicrobial activity was tested by using micro broth dilution methods to determine minimum inhibitory concentration (MIC). Molecular identification into level genera and species was determined by 16S rRNA gene sequencing. Out of 16 actinomycetes isolates used, 4 isolates have activity against Candida albicans ATCC 10231, Staphylococcus aureus ATCC 6538, Bacillus subtilis BTCC B-612, and Escherichia coli BTCC B-614, specifically InaCC A758, InaCC A759, InaCC A760 and InaCC A765 isolates. InaCC A758 have highest antimicrobial activity against mentioned microbial with MIC value at 50 μg/mL, 6.25 μg/mL, 31.25 μg/mL and 3.125 μg/mL, respectively. Three genera were found from the samples: i.e. Streptomyces (80%), Microbispora (13%) and Nocardia (6%). Based on 16S rRNA gene identification, the active isolates of actinomycetes InaCC A758, InaCC A759, InaCC A760 and InaCC A765 were similar to Streptomyces badius, Streptomyces olivaceus, Streptomyces sanyensis, and Nocardia otitidiscaviarum, respectively. The secondary metabolites of actinomycetes extracts from Pramuka Island can be potentially developed as antifungal and antibacterial agents.

Damayanti E, Lisdiyanti P, Sundowo A, Ratnakomala S, Dinoto A, Widada J, Mustofa. 2021. Antiplasmodial activity, biosynthetic gene clusters diversity, and secondary metabolite constituent of selected Indonesian Streptomyces. Biodiversitas 22: 3478-3487. Actinobacteria of the genus Streptomyces are known as the primary candidate antibiotics, but still limited for antiplasmodial drugs. This study aimed to investigate the antiplasmodial activity, the biosynthetic gene clusters (BGCs) diversity, and the secondary metabolites constituent of selected Indonesian Streptomyces. The bacteria were isolated from various habitats: karst soil (GMR22), mangrove sediments (BSE7F and SHP 22-7), and marine sediment (GMY01). Molecular identification by 16S rDNA sequencing were performed for confirmation and morphological characterization by scanning electron microscope (SEM) were performed for identification. In vitro antiplasmodial assay was performed on human Plasmodium falciparum FCR-3. The BGCs which encode secondary metabolites were analysed using antiSMASH version 5 based on available whole genome sequence (WGS) data. The secondary metabolites were obtained from liquid fermentation followed by extraction using methanol and ethyl acetate. The secondary metabolites constituent was determined by liquid chromatography tandem mass spectrometry (LC-MS/MS). The molecular identification showed that GMR22 had similarity to Streptomyces lactacystinicus (98.02%), while BSE7F was similar to Streptomyces althioticus (97.06%), SHP 22-7 was similar to Streptomyces rochei (94.84%), and GMY01 to Streptomyces odonnellii (98.57%). All of isolates had morphological characteristics as the genus Streptomyces bacteria. The highest Plasmodium inhibition (81.84 ± 3.5%) was demonstrated by ethyl acetate extract of marine-derived Streptomyces sp. GMY01 (12.5 µg/mL). Non-ribosomal polyketide synthetase (NRPS), polyketide synthase (PKS) and hybrid of NRPS-PKS were the major BGCs in all Streptomyces. Majority of the Streptomyces produced compounds containing CHON elements with molecular weight approximately 100-400 Da. The active extract of GMY01 bacterium had five major detected compounds, namely kuraramine (C12H18N2O2), laminine (C9H20N2O2) 2-ethylacetanilide (C10H13NO), propoxur (C11H15NO3), and 3-methyl-1,2-diphenylbutan-1-one (C17H18O). This Indonesian marine bacterium is potential for bioassay guided isolation of antiplasmodial compounds in the future studies.

Amylolytic actinobacteria were isolated from the rumen fluid of ruminants. Eighteen isolates actinobacteria were obtained and the generation of actinobacteria mutants using chemical agent Sodium Azide. The actinobacteria wild type and mutants were then screened for amylase activity using starch agar plate assay. Ten isolates showed the ability to produce amylase enzymes. Submerged fermentation (SmF) was used for microbial production of amylase. It was found that maximum amylase activity (2.53 U/mL) was produced by actinobacteria isolate R-9 M, and 2.43 U/mL was produced by isolate R-2 WT using pollard as a substrate in Submerged fermentation. This preliminary study could provide base information for the discovery of novel actinobacteria from natural resources such as rumen fluid for the production of amylase, which will be used for multipurpose.