Secondary Metabolite Production Potential of Mangrove-Derived Streptomyces olivaceus

Mangroves are intertidal extreme environments with rich microbial communities. Actinobacteria are well known for producing antibiotics. The search for biosynthetic potential of Actinobacteria from mangrove environments could provide more possibilities for useful secondary metabolites. In this study, whole genome sequencing and MS/MS analysis were used to explore the secondary metabolite production potential of one actinobacterial strain of Streptomyces olivaceus sp., isolated from a mangrove in Macau, China. The results showed that a total of 105 gene clusters were found in the genome of S. olivaceus sp., and 53 known secondary metabolites, including bioactive compounds, peptides, and other products, were predicted by genome mining. There were 28 secondary metabolites classified as antibiotics, which were not previously known from S. olivaceus. ISP medium 2 was then used to ferment the S. olivaceus sp. to determine which predicted secondary metabolite could be truly produced. The chemical analysis revealed that ectoine, melanin, and the antibiotic of validamycin A could be observed in the fermentation broth. This was the first observation that these three compounds can be produced by a strain of S. olivaceus. Therefore, it can be concluded that Actinobacteria isolated from the mangrove environment have unknown potential to produce bioactive secondary metabolites.

Molecular identification and antibiotic resistance pattern of actinomycetes isolates among immunocompromised patients in Iran, emerging of new infections

Recent advancements in DNA-based approaches have led to the identification of uncommon and rare bacterial pathogens. In this study, by utilizing a DNA-based approach, a total of 1043 clinical specimens were processed for the identification of actinobacteria targeting the 16S rRNA and gyrB genes. Drug susceptibility testing was also conducted using micro-broth dilution and PCR. Two isolates of Nocardia flavorosea and Rhodococcus erythropolis were reported for the first time in Iran. Also, Nocardiopsis dassonvillei, Streptomyces olivaceus, and Streptomyces griseus were reported for the first time in Asia. Infections caused by Nocardia caishijiensis and Prauserella muralis have also been reported in this study. The first Asian case of pulmonary infection caused by Nocardia ignorata and the first global case of brain abscess caused by Nocardia ninae and Nocardia neocaledoniensis have been reported in this study. Overall 30 isolates belonging to 6 genera (Nocardia, Streptomyces, Rodoccoccus, Nocardiopsis, Rothia, and Prauserella) were detected in 30 patients. All 30 isolates were susceptible to amikacin and linezolid. Three isolates including Nocardia otitidiscaviarum (n = 2) and Nocardia flavorosea (n = 1) were resistant to trimethoprim-sulfamethoxazole which were the first trimethoprim-sulfamethoxazole resistant clinical actinomycetes in Iran. Isolation of rare species of actinomycetes particularly Nocardia spp. requires urgent action before they spread clinically particularly among immunocompromised patients.

The potency of actinomycetes extracts isolated from Pramuka Island, Jakarta, Indonesia as antimicrobial agents

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.

Genome Sequencing of Streptomyces olivaceus SCSIO T05 and Activated Production of Lobophorin CR4 via Metabolic Engineering and Genome Mining

Marine-sourced actinomycete genus Streptomyces continues to be an important source of new natural products. Here we report the complete genome sequence of deep-sea-derived Streptomyces olivaceus SCSIO T05, harboring 37 putative biosynthetic gene clusters (BGCs). A cryptic BGC for type I polyketides was activated by metabolic engineering methods, enabling the discovery of a known compound, lobophorin CR4 (1). Genome mining yielded a putative lobophorin BGC (lbp) that missed the functional FAD-dependent oxidoreductase to generate the d-kijanose, leading to the production of lobophorin CR4 without the attachment of d-kijanose to C17-OH. Using the gene-disruption method, we confirmed that the lbp BGC accounts for lobophorin biosynthesis. We conclude that metabolic engineering and genome mining provide an effective approach to activate cryptic BGCs.