Analyzing the biosynthetc potental of antmicrobial‐producing actnobacteria originatng from Indonesia Anissa Utami 1,6 , Pamela Apriliana 2 , Yudi Kusnadi 3,7 , Dewi S. Zilda 3 , Zidny Ilmiah 2 , Puspita Lisdiyant 2 , Siswa Setyahadi 1,4,* , Agustnus R. Uria 3,5,* 1 Graduate School of Pharmacy, Pancasila University, Jl. Raya Lenteng Agung, Jakarta Selatan 12630, Indonesia 2 Research Center for Biotechnology, Indonesian Insttute of Sciences (LIPI), Jl. LIPI, Cibinong, Bogor, Jawa Barat 16911, Indonesia 3 Research Center for Marine and Fisheries Product processing and Biotechnology Ministry of Marine Afairs and Fisheries, JL. KS Tubun Petamburan VI, Slipi, Jakarta Pusat 10260, Indonesia 4 Center of Bio‐industrial Technology, Agency for Technology Assessment and Development, Tangerang Selatan, Banten 15314, Indonesia 5 Faculty of Pharmaceutcal Sciences, Hokkaido University, Kita Ward, Sapporo, Hokkaido 060‐0812, Japan 6 Politeknik Hang Tuah Jakarta, Jl. Bendungan Hilir Jakarta Pusat 10210, Indonesia 7 Life Science Division, ITS Science Indonesia, Jl. Boulevard Artha Gading, Jakarta Utara 14240, Indonesia *Corresponding author: siswa.setyahadi@bppt.go.id; auria@pharm.hokudai.ac.jp SUBMITTED 13 April 2021 REVISED 7 May 2021 ACCEPTED 4 June 2021 ABSTRACT We investgated the biosynthetc potental of soil‐associated actnobacteria originatng from Indonesia, identfed as Streptomyces luridus and as Streptomyces luteosporeus. Antmicrobial assays indicated inhibitory actvity by both strains against the pathogen Pseudomonas aeruginosa, with S. luteosporeus partcularly inhibitng the growth of Bacillus subtlis. PCR‐amplifcaton, cloning, and sequencing of ketosynthase (KS) domains of type I modular polyketde (PKS‐I) and adenylaton (AD) domains of non‐ribosomal peptde synthetase (NRPS) indicated the diversity of KS and AD domains derived from both Indonesian Streptomyces. Further phylogenetc analysis showed that KS domains from the subclass cis‐AT PKS can be classifed as being a part of a loading module or an extension module, along with their predicted substrate specifcity. The results suggest that both strains are a potental source of novel biosynthetc pathways. This genetc anal‐ ysis approach can be used as a fast guide to obtain insight into natural product biosynthetc gene diversity in microorganisms. KEYWORDS Antmicrobial actvity; biosynthetc potental; Streptomyces luridus; Streptomyces luteosporeus; PKS and NRPS gene di‐ versity Indonesian Journal of Biotechnology VOLUME 26(3), 2021, 142‐151 | RESEARCH ARTICLE 1. Introducton Phylum Actinobacteria have long been recognized as the major source of compounds representing 45% of all bioac tive microbial metabolites discovered so far (Bérdy 2005). Many actinobacterial natural products belong to polyke tides and nonribosomal peptides, two large classes of natural products with various potent biological activities, such as antitumor, antivirus, antibiotics, and immune suppressants (Cane and Walsh 1999). From the biosyn thetic point of view, the huge diversity of most polyke tide structures is generated from simple carboxylic acid monomers via a series of enzymatic reactions mediated by polyketide synthases (PKSs) (Risdian et al. 2019; Her tweck 2015). Risdian et al. (2019) stated that among three types of bacterial PKSs known to date (types I, II, and III), type I PKS (PKSI) in Streptomyces has at tracted increasing attention due to the involvement of this type in the biosynthesis of many macrocyclic polyketides (macrolides) with various bioactivities. Type I PKS system consists of modules, which act in a noniterative way. Each module harbors a set of cat alytic domains that are responsible for one cycle of polyke tide elongation and modification. A module minimally consists of three domains: an acyltransferase (AT) do main, an acyl carrier protein (ACP) domain, and a ketoacyl synthase (KS) domain (Hertweck 2009; Rawlings 2001). Each module receives an acyl chain from the upstream module onto KS domain and a suitable extender unit onto ACP through acyltransferase (AT) activity. ACP in this module serves as an anchor for the building block. Sub sequent KScatalyzed addition of the extender unit to the acyl chain results in a polyketide product that can be mod ified by optional domains such as ketoreductase (KR), de hydratase (DH), and enoylreductase (ER) (Watanabe et al. 2003; Weissman 2015). Due to the highly conserved re gions and intermediate specificity of KS domains in PKS systems, KS sequences are ideally used as a basis not only Indones J Biotechnol 26(3), 2021, 142‐151 | DOI 10.22146/ijbiotech.65239 www.jurnal.ugm.ac.id/ijbiotech Copyright © 2021 THE AUTHOR(S). This artcle is distributed under a Creatve Commons Atributon‐ShareAlike 4.0 Internatonal license.