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Polyene macrolactams are a special group of natural products with great diversity, unique structural features, and a wide range of biological activities. Herein, a cryptic gene cluster for the biosynthesis of putative macrolactams was disclosed from a sponge-associated bacterium, Streptomyces sp. DSS69, by genome mining. Cloning and heterologous expression of the whole biosynthetic gene cluster led to the discovery of weddellamycin, a polyene macrolactam bearing a 23/5/6 ring skeleton. A negative regulator, WdlO, and two positive regulators, WdlA and WdlB, involved in the regulation of weddellamycin production were unraveled. The fermentation titer of weddellamycin was significantly improved by overexpression of wdlA and wdlB and deletion of wdlO . Notably, weddellamycin showed remarkable antibacterial activity against various Gram-positive bacteria including MRSA, with MIC values of 0.10-0.83 μg/mL, and antifungal activity against Candida albicans , with an MIC value of 3.33 μg/mL. Weddellamycin also displayed cytotoxicity against several cancer cell lines, with IC 50 values ranging from 2.07 to 11.50 µM.

Twelve new polyenic macrolactams, cyclamenols G-R ( 1 and 3 - 13 ), together with the known analogue cyclamenol A ( 2 ), were isolated from Streptomyces sp. OUCMDZ-4348. Their structures were elucidated by spectroscopic analysis, quantum chemical calculations, chemical derivatizations, and Mosher's methods. The sequenced genome of OUCMDZ-4348 revealed the putative biosynthetic gene cluster of cyclamenols. It was proposed that the polycyclic natural products, cyclamenols H-R, might be formed from cyclamenols A and G through nonenzymatic intramolecular cycloadditions and oxidative cyclizations.

Molecular studies led to the resurgence of natural products research from genus Streptomyces, already known for their long history and importance for the pharmaceutical industry. However, species belonging to this genus are difficult to identify and the most commonly used techniques, which are based on 16S rRNA sequencing, do not discriminate between related species. In this work, amplification profiles generated from BOX-PCR and REP-PCR of 49 Antarctic soil streptomycetes were compared to evaluate the diversity present in the group and to characterize the bacterial isolates, along with some 16S rRNA amplifications. The BOX-A1R primer exhibit clearer amplification fragments, different from the amplification patterns obtained using the REP 1R and 2R primers. A higher diversity was observed with REP-PCR amplifications, even though a larger number of fragments was obtained with BOX-A1R primer amplifications. There are at least four isolates that showed great similarity (about 90%) in both techniques. In other hand, there are two others that are 90% similar in BOX-PCR, but distant in REP-PCR, showing only 40% of similarity. Results of the combination of BOX-PCR and REP-PCR represent a simple and low-cost method to discriminate between Streptomyces strains. There is no species identification with only the 16S rRNA, most isolates seem to be related to S. globisporus. Further studies added to the obtained results may provide better data to help the characterization of these microorganisms.

Objective: A polar marine actinobacterium (XE-1) was selected and used to produce a protease with special characteristics., Methods: The XE-1 was identified as Streptomyces based on morphological, biochemical and molecular characterizations (16S rRNA gene sequence analysis). The protease was purified by 3 purification steps, including ethanol precipitation, ion exchange and gel chromatography. Its apparent molecular mass was estimated by SDS-PAGE., Results: A solvent, detergent and oxidizing agent stable alkaline serine protease (with a low weight molecular, 14 kDa by SDS-PAGE) , secreted by strain XE-1, was purified and characterized. The protease was stable in the pH range between 5 and 10, with optimal pH 8.2 and optimal temperature 55 degrees C. K(m) and V(max) towards casein activity were 1.9 mg/mL and 973 U/mL, respectively. The protease was more active and stable in various hydrophilic organic solvents (such as dimethylformamid and toluene). Moreover, it was also active and stable in bleaching agents (such as hydrogen peroxide) ; and stable in denaturant agents (such as urea and guanidine hydrochloride) at the concentration from 0.2 mol/L to 4 mol/L, which were the new characteristics., Conclusion: These biochemical characteristics suggest this enzyme has the potential value in numerous industrial applications.

A novel actinomycete strain, GW25-5(T), was isolated from a soil sample collected from the Fildes Peninsula, King George Island, West Antarctica. The strain was characterized by white to grey aerial mycelia, which were differentiated to straight to flexuous spore chains, with rod-shaped smooth spores. The cell wall of strain GW25-5(T) contained LL-diaminopimelic acid (A(2)pm) and traces of meso-A(2)pm. Whole-cell sugars were galactose and minor amounts of mannose and glucose. The predominant menaquinones were MK-9(H(6)) (49%), MK-9(H(8)) (24%) and MK-9(H(4)) (12%). The phospholipids contained DPG, PE, PI, PIM and PL(s). The major cellular fatty acids were iso-C(16:0) and anteiso-C(15:0). Genomic DNA G+C content of strain GW25-5(T) was 70.0 mol%. BLAST result showed that strain GW25-5 has the 16S rRNA gene sequence highest similarity of 97.5% with members of genus Streptomyces and phylogenetic analysis indicated that this strain belongs to the genus Streptomyces. DNA-DNA relatedness values of strain GW25-5(T) with the closest species of Streptomyces purpureus LMG 19368(T) and Streptomyces beijiangensis YIM 6(T) were significantly lower than 70% of the threshold value for the delineation of genomic species. A polyphasic taxonomic investigation based on a judicious combination of genotypic and phenotypic characteristics revealed that the organism represents a novel species of the genus Streptomyces. Thus, we propose strain GW25-5(T) as the type strain of this novel species, Streptomyces fildesensis (=CGMCC 4.5735(T) = YIM 93602(T) = DSM 41987(T) = NRRL B 24828(T)).

As part of an enzyme-screening programme, an actinobacterium, strain HSM#10T, was isolated from a sample collected from the base of a translucent quartz rock in Miers Valley, eastern Antarctica. The isolate produced branching vegetative mycelium that was characteristic of filamentous actinobacteria. The chemotaxonomic characteristics of the strain suggested that HSM#10T should be classified as a member of the genus Streptomyces. Furthermore, phylogenetic analysis based on 16S rRNA gene sequences showed that the strain was closely related to members of the genus Streptomyces, which supports the classification of this strain within the family Streptomycetaceae. Phenotypic and phylogenetic results allowed strain HSM#10T to be differentiated from known streptomycetes. DNA-DNA hybridization data also showed that strain HSM#10T could be differentiated from its nearest phylogenetic neighbours Streptomyces chryseus DSM 40420T (53.55+/-3.15% DNA relatedness), Streptomyces helvaticus DSM 40431T (38.75+/-2.75%), Streptomyces flavidovirens DSM 40150T (30.7+/-2.90%) and Streptomyces albidochromogenes DSM 41800T (33.9+/-0.10%). Therefore, the name Streptomyces hypolithicus sp. nov. is proposed, with HSM#10T (=DSM 41950T=NRRL B-24669T) as the type strain.

Polar organisms should have mechanisms to survive the extremely cold environment. Four genes encoding cold-shock proteins, which are small, cold-induced bacterial proteins, have been cloned from the Antarctic bacterium Streptomyces sp. AA8321. Since the specific functions of any polar bacterial or Streptomyces cold-shock proteins have not yet been determined, we examined the role of cold-shock protein A from Streptomyces sp. AA8321 (CspA(St)). Gel filtration chromatography showed that purified CspA(St) exists as a homodimer under physiological conditions, and gel shift assays showed that it binds to single-stranded, but not double-stranded, DNA. Overexpression of CspA(St) in Escherichia coli severely impaired the ability of the host cells to form colonies, and the cells developed an elongated morphology. Incorporation of a deoxynucleoside analogue, 5-bromo-2'-deoxyuridine, into newly synthesized DNA was also drastically diminished in CspA(St)-overexpressing cells. These results suggest that CspA(St) play a role in inhibition of DNA replication during cold-adaptation.