Streptomyces hyderabadensis sp. nov., an actinomycete isolated from soil

Streptomyces salinarius sp. nov., an actinomycete isolated from solar saltern soil

An actinobacterium, designated strain SS06011^T, was isolated from solar saltern soil collected from Samut Sakhon province, Thailand. The taxonomic position of this strain was established using the polyphasic taxonomic approach. The strain produced grey aerial spore mass on International Streptomyces Project 2 seawater agar that differentiated into spiral spore chains with rugose-surfaced spores. Strain SS06011^T was found to have ll-diaminopimelic acid in the cell peptidoglycan. Whole-cell hydrolysates contained galactose, glucose and ribose. MK-9(H₆) and MK-9(H₄) were major menaquinones. The major cellular fatty acids comprised iso-C_16 : 0, anteiso-C_15 : 0 and anteiso-C_17 : 0. Diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol and phosphatidylinositol were detected in cells. These characteristics were coincident with the typical morphological and chemotaxonomic properties of the genus Streptomyces. The taxonomic affiliation at the genus level of this strain could also be confirmed by its 16S rRNA gene sequence data. Strain SS06011^T showed the highest 16S rRNA gene sequence similarity to Streptomyces ardesiacus NRRL B-1773^T (99.1 %), Streptomyces coelicoflavus NBRC 15399^T (99.1 %) and Streptomyces hyderabadensis OU-40^T (99.1 %). Digital DNA-DNA hybridization (dDDH), average nucleotide identity-blast (ANIb) and average amino acid identity (AAI) values between strain SS06011^T and its closely related type strains, S. ardesiacus NBRC 15402^T, S. coelicoflavus NBRC 15399^T and S. hyderabadensis JCM 17657^T, were in the range of 45.4-48.4 % (for dDDH), 90.8-91.9 % (for ANIb) and 90.8-91.7 % (for AAI), respectively, which are lower than the cut-off criteria for species delineation. The DNA G+C content of genomic DNA was 71.9 mol%. With the differences in physiological, biochemical and genotypic data, strain SS06011^T could be discriminated from its closest neighbours. Thus, strain SS06011^T should be recognized as representing a novel species of the genus Streptomyces, for which the name Streptomyces salinarius sp. nov. is proposed. The type strain is SS06011^T (=TBRC 9951^T=NBRC 113998^T).

Use of soil actinomycetes for pharmaceutical, food, agricultural, and environmental purposes

In this article, we reviewed the international scientific production of the last years on actinomycetes isolated from soil aiming to report recent advances in using these microorganisms for different applications. The most promising genera, isolation conditions and procedures, pH, temperature, and NaCl tolerance of these bacteria were reported. Based on the content analysis of the articles, most studies have focused on the isolation and taxonomic description of new species of actinomycetes. Regarding the applications, the antimicrobial potential (antibacterial and antifungal) prevailed among the articles, followed by the production of enzymes (cellulases and chitinases, etc.), agricultural uses (plant growth promotion and phytopathogen control), bioremediation (organic and inorganic contaminants), among others. Furthermore, a wide range of growth capacity was verified, including temperatures from 4 to 60 °C (optimum: 28 °C), pH from 3 to 13 (optimum: 7), and NaCl tolerance up to 32% (optimum: 0-1%), which evidence a great tolerance for actinomycetes cultivation. Streptomyces was the genus with the highest incidence among the soil actinomycetes and the most exploited for different uses. Besides, the interest in isolating actinomycetes from soils in extreme environments (Antarctica and deserts, for example) is growing to explore the adaptive capacities of new strains and the secondary metabolites produced by these microorganisms for different industrial interests, especially for pharmaceutical, food, agricultural, and environmental purposes.

Production of a broad spectrum streptothricin like antibiotic from halotolerant Streptomyces fimbriatus isolate G1 associated with marine sediments

Streptomyces have been reported as a remarkable source for bioactive secondary metabolites with complex structural and functional diversity. In this study, 35 isolates of genus Streptomyces were purified from rhizospheric and marine soils collected from previously unexplored habitats and screened for antimicrobial activities. One of these isolates, G1, when tested in vitro, was found highly active against wide range of microbes including Gram-positive, Gram-negative bacteria, and different fungal pathogens. It was identified as mesophilic, alkaliphilic, and moderately halotolerant as it showed optimum growth at temperature 30 °C, pH 8.0 in casein-starch-peptone-yeast extract-malt extract medium supplemented with 5% NaCl. Sequence analysis of the 16S rRNA gene indicated 100% identity of this isolate to Streptomyces fimbriatus. Moreover, maximum antimicrobial activity was achieved in starch nitrate medium supplemented with 1% glycerol as carbon and 0.03% soy meal as nitrogen source. The antimicrobial compounds produced by this isolate were extracted in methanol. Bioassay-guided fractionation through thin layer chromatography of methanolic extract resulted in the separation of a most active fraction with an R_f value of 0.46. This active fraction was characterized by FTIR and LCMS analysis and found similar to streptothricin D like antibiotic with m/z 758.42.

Complete genome sequence of Streptomyces sp. HSG2 from rhizosphere soil of mangrove in Qingmei Gang, Sanya

Streptomyces sp. HSG2 was isolated from rhizosphere soil of a mangrove forest sample at Qingmei Gang, Sanya. The complete genome sequence of the strain HSG2 was obtained using PacBio Sequel HGAP.4 and comprised of 5,282,528 base pairs with a 71.9 mol% G + C content, 4504 protein-coding genes, and 71 RNAs. An in-silico analysis confirmed that genes associated with polysaccharide hydrolyzation, hydrocarbon degradation, and aerobic denitrification were presented in the genome. We also identified 24 natural product biosynthetic gene clusters for secondary metabolites, including those for streptobactin and nystatin A1. The complete genome sequence indicated that Streptomyces sp. HSG2 will provide insight into the biosynthesis and regulatory mechanisms for its secondary metabolites, and propose a potential use in biotechnological and novel bioactive natural product biosynthetic applications.

Diversity of Streptomyces spp. from mangrove forest of Sarawak (Malaysia) and screening of their antioxidant and cytotoxic activities

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.

Optimization of the Cytotoxic Activity of Three Streptomyces Strains Isolated from Guaviare River Sediments (Colombia, South America)

Three Streptomyces strains isolated from Guaviare sediments (Colombia, South America) with cytotoxic activity against prostate cancer (PC3), breast cancer (MDA-MB-231), and lung cancer (A549) line cells were studied. The present investigation reveals the enhancement of the cytotoxic activity evaluating different values of pH, carbon sources (sucrose, glucose, xylose, maltose, and starch), and nitrogen sources (malt extract, yeast extract, meat extract, peptone, and potassium nitrate). Based on the response surface methodology, the isolates Streptomyces aburaviensis (73) had the maximum activity for lung cancer (IC50= 25.00 ± 1.86 ppm) with 4% of yeast extract, 3% of starch, and a pH value of 7. Streptomyces gramineus (386) had the maximum activity against prostate cancer (IC50= 6.14 ± 2.07 ppm) with 5% of malt extract, 3% of glucose, and a pH value of 6. Finally, Streptomyces psammoticus (519) had the maximum activity against breast cancer (IC50= 35.53 ± 2.71 ppm) with 1% of yeast extract, 4% of starch, and a pH 8. The results suggest that the ethyl acetate extracts from isolates Streptomyces aburaviensis (73), Streptomyces gramineus (386), and Streptomyces psammoticus (519) have a potential for use in pharmaceuticals as cytotoxic agents.

Streptomyces leeuwenhoekii sp. nov., the producer of chaxalactins and chaxamycins, forms a distinct branch in Streptomyces gene trees

A polyphasic study was carried out to establish the taxonomic status of an Atacama Desert isolate, Streptomyces strain C34(T), which synthesises novel antibiotics, the chaxalactins and chaxamycins. The organism was shown to have chemotaxonomic, cultural and morphological properties consistent with its classification in the genus Streptomyces. Analysis of 16S rRNA gene sequences showed that strain C34(T) formed a distinct phyletic line in the Streptomyces gene tree that was very loosely associated with the type strains of several Streptomyces species. Multilocus sequence analysis based on five house-keeping gene alleles underpinned the separation of strain C34(T) from all of its nearest phylogenetic neighbours, apart from Streptomyces chiangmaiensis TA-1(T) and Streptomyces hyderabadensis OU-40(T) which are not currently in the MLSA database. Strain C34(T) was distinguished readily from the S. chiangmaiensis and S. hyderabadensis strains by using a combination of cultural and phenotypic data. Consequently, strain C34(T) is considered to represent a new species of the genus Streptomyces for which the name Streptomyces leeuwenhoekii sp. nov. is proposed. The type strain is C34(T) (= DSM 42122(T) = NRRL B-24963(T)). Analysis of the whole-genome sequence of S. leeuwenhoekii, with 6,780 predicted open reading frames and a total genome size of around 7.86 Mb, revealed a high potential for natural product biosynthesis.

Interaction of pyrrolobenzodiazepine (PBD) ligands with parallel intermolecular G-quadruplex complex using spectroscopy and ESI-MS

Studies on ligand interaction with quadruplex DNA, and their role in stabilizing the complex at concentration prevailing under physiological condition, has attained high interest. Electrospray ionization mass spectrometry (ESI-MS) and spectroscopic studies in solution were used to evaluate the interaction of PBD and TMPyP4 ligands, stoichiometry and selectivity to G-quadruplex DNA. Two synthetic ligands from PBD family, namely pyrene-linked pyrrolo[2,1-c][1,4]benzodiazepine hybrid (PBD1), mixed imine-amide pyrrolobenzodiazepine dimer (PBD2) and 5,10,15,20-tetrakis(N-methyl-4-pyridyl)porphyrin (TMPyP4) were studied. G-rich single-stranded oligonucleotide d(5'GGGGTTGGGG3') designated as d(T(2)G(8)), from the telomeric region of Tetrahymena Glaucoma, was considered for the interaction with ligands. ESI-MS and spectroscopic methods viz., circular dichroism (CD), UV-Visible, and fluorescence were employed to investigate the G-quadruplex structures formed by d(T(2)G(8)) sequence and its interaction with PBD and TMPyP4 ligands. From ESI-MS spectra, it is evident that the majority of quadruplexes exist as d(T(2)G(8))(2) and d(T(2)G(8))(4) forms possessing two to ten cations in the centre, thereby stabilizing the complex. CD band of PBD1 and PBD2 showed hypo and hyperchromicity, on interaction with quadruplex DNA, indicating unfolding and stabilization of quadruplex DNA complex, respectively. UV-Visible and fluorescence experiments suggest that PBD1 bind externally where as PBD2 intercalate moderately and bind externally to G-quadruplex DNA. Further, melting experiments using SYBR Green indicate that PBD1 unfolds and PBD2 stabilizes the G-quadruplex complex. ITC experiments using d(T(2)G(8)) quadruplex with PBD ligands reveal that PBD1 and PBD2 prefer external/loop binding and external/intercalative binding to quadruplex DNA, respectively. From experimental results it is clear that the interaction of PBD2 and TMPyP4 impart higher stability to the quadruplex complex.