A novel actinomycete, strain 1_25(T), was isolated from soil under a black Gobi rock sample from Shuangta, PR China, and characterized using a polyphasic taxonomic approach. The results of comparative analysis of the 16S rRNA gene sequences indicated the 1_25(T) represented a member of the genus Streptomyces. Chemotaxonomic data revealed that 1_25(T) possessed MK-9(H-8) as the major menaquinone. The cell wall contained LL-diaminopimelic acid (LL-DAP) and the whole-cell sugar pattern consisted of ribose, glucose and galactose. Major fatty acid methyl esters were observed to be iso-C-16:0 (23.6%), and anteiso-C-15:0 (10.4%). The genomic DNA G+C content of 1_25(T) was 69 mol%. The results of phylogenetic analysis based on 16S rRNA gene sequence indicated that 1_25(T) had high sequence similarity with Streptomyces qinglanensis 172205(T) (98.1%), Streptomyces lycii TRM 66187(T) (98 %), and Streptomyces griseocarneus JCM4580(T) (98 %). In addition to the differences in phenotypic characters, the average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between 1_25(T) and closely related species were below the recommended threshold values for assigning strains to the same species. The fermentation product of 1_25(T) in ISP2 had an inhibitory effect on Staphylococcus aureus. On the basis of these genotypic and phenotypic characteristics, strain 1_25(T) (=JCM 34936(T)=GDMCC 4.216(T)) represents a novel species of the genus Streptomyces, for which the name Streptomyces gobiensis sp. nov. is proposed.

Streptomyces from unexplored or underexplored environments may be an essential source of discoveries of bioactive molecules. One such example is Streptomyces qaidamensis S10(T), which was isolated from a sand sample collected in Qaidam Basin, Qinghai Province, China. Here, we report on (+/-)-differolide, an antioxidant isolated from S. qaidamensis, and verified with scavenging experiments on 2,2-diphenyl-1-picrylhydrazyl (DPPH). The biosynthetic gene cluster responsible for synthesizing the compound was also identified using comparative genomic methods. These results provide a basis for further study of the biological activities of (+/-)-differolide, which also make it possible to develop as an antioxidant medicine.

The harsh climatic conditions of deserts may lead to unique adaptations of microbes, which could serve as potential sources of new metabolites to cope with environmental stresses. However, the mechanisms governing the environmental adaptability and antimicrobial activity of desert Streptomyces remain inadequate, especially in extreme temperature differences, drought conditions, and strong radiation. Here, we isolated a Streptomyces strain from rocks in the Kumtagh Desert in Northwest China and tested its antibacterial activity, resistance to UV-C irradiation, and tolerance to hydrogen peroxide (H2O2). The whole-genome sequencing was carried out to study the mechanisms underlying physiological characteristics and ecological adaptation from a genomic perspective. This strain has a growth inhibitory effect against a variety of indicator bacteria, and the highest antibacterial activity recorded was against Bacillus cereus. Moreover, strain D23 can withstand UV-C irradiation up to 100 J/m(2) (D10 = 80 J/m(2)) and tolerate stress up to 70 mM H2O2. The genome prediction of strain D23 revealed the mechanisms associated with its adaptation to extreme environmental and stressful conditions. In total, 33 biosynthetic gene clusters (BGCs) were predicted based on anti-SMASH. Gene annotation found that S. huasconensis D23 contains several genes and proteins associated with the biosynthesis of factors required to cope with environmental stress of temperature, UV radiation, and osmotic pressure. The results of this study provide information about the genome and BGCs of the strain S. huasconensis D23. The experimental results combined with the genome sequencing data show that antimicrobial activity and stress resistance of S. huasconensis D23 was due to the rich and diverse secondary metabolite production capacity and the induction of stress-responsive genes. The environmental adaptability and antimicrobial activity information presented here will be valuable for subsequent work regarding the isolation of bioactive compounds and provide insight into the ecological adaptation mechanism of microbes to extreme desert environments.

A novel Streptomyces strain, designated 3_2(T), was isolated from soil under the black Gobi rock sample of Northwest China. The taxonomic position of this strain was revealed by a polyphasic approach. Comparative analysis of the 16S rRNA gene sequences indicated that 3_2(T) was closely related to the members of the genus Streptomyces, with the highest similarity to Streptomyces rimosus subsp. rimosus CGMCC 4.1438 (99.17%), Streptomyces sioyaensis DSM 40032 (98.97%). Strain 3_2(T) can grow in media up to 13% NaCl. The genomic DNA G + C content of strain 3_2(T) was 69.9%. We obtained the genomes of 22 Streptomyces strains similar to strain 3_2(T), compared the average nucleotide similarity, dDDH and average amino acid identity, and found that the genomic similarity of the new isolate 3_2(T) to all strains was below the threshold for interspecies classification. Chemotaxonomic data revealed that strain 3_2(T) possessed MK-9 (H-6) and MK-9 (H-8) as the major menaquinones. The cell wall contained LL-diaminopimelic acid (LL-DAP) and the whole-cell sugars were ribose and glucose. The major fatty acid methyl esters were iso-C-16:0 (23.6%) and anteiso-C-15:0 (10.4%). The fermentation products of strain 3_2(T) were inhibitory to Staphylococcus aureus and Bacillus thuringiensi. The genome of 3_2(T) was further predicted using anti-smash and the strain was found to encode the production of 41 secondary metabolites, and these gene clusters may be key to the good inhibitory activity exhibited by the strain. Genomic analysis revealed that strain 3_2(T) can encode genes that produce a variety of genes in response to environmental stresses, including cold shock, detoxification, heat shock, osmotic stress, oxidative stress, and these genes may play a key role in the harsh environment in which the strain can survive. Therefore, this strain represents a novel Streptomyces species, for which the name Streptomyces halobius sp. nov. is proposed. The type strain is 3_2(T) (= JCM 34935(T) = GDMCC 4.217(T)).