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 genus Arthrobacter is a source of many natural products that are critical in the development of new medicines. Here, we isolated a novel carotenoid from Arthrobacter sp. QL17 and characterized its properties. The carotenoid was extracted with methanol, and purified by column chromatography and semi-preparative HPLC. Based on micrOTOF-Q and NMR analyses, the pigment was chemically characterized as 2,2 '-((((1E,3E,5E,7E,9E,11E,13E,15E,17E,19E)-3,7,14,18-tetramethylicosa-1,3,5,7,9,11,13,15,17,19-decaene-1,20-diyl)bis(2,2,4-trimethylcyclohex-3-ene-3,1-diyl)) bis(ethan-2-yl-1-ylidene))bi(propane-1,3-diol), and named arthroxanthin. The biological activities of arthroxanthin were evaluated with DPPH, ABTS and MTT assays. Arthroxanthin exhibited excellent radical scavenging properties, as shown for 2, 20-diphenyl-1-picrylhydrazyl (DPPH) and 2,2-n-(3,2-ethyl-benzothiazole-6-sulfonic acid) ammonium salt (ABTS), respectively, with IC50s of 69.8 and 21.5 mu g/mL. It also showed moderate anticancer activities against HepG2, Hela, MDAB-231, SW480, and MKN-45 with IC50 values of 107.6, 150.4, 143.4, 195.9, and 145.5 mu g/mL, respectively. Therefore, arthroxanthin derived from Arthrobacter sp. QL17 may be a potent antioxidant and anticancer agent for food and pharmaceutical use.

Spring, especially the freeze-thaw season, is considered the key period for the growth and carbon sequestration of desert mosses. It is not clear how the change in environment water and temperature affects the physiological characteristics of desert mosses in freeze-thaw season. In this study, the effects of water and freeze-thaw cycles on the physiological characteristics of Syntrichia caninervis were assessed by manipulating the increase or removal of 65% snow and changes in the freeze-thaw cycles. The results showed that the changes in snow depth, freeze-thaw cycles, and their interaction significantly affected the plant water content, osmoregulatory substances content, antioxidant substance, and antioxidant enzyme activities. The contents of free proline, soluble sugar, ascorbic acid (AsA), reduced glutathione (GSH), and malondialdehyde (MDA), and superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activities increased significantly with the decrease in snow depth and freeze-thaw cycles. POD and free proline were the most sensitive to the snow depth and freeze-thaw cycles, while SOD and CAT were the least sensitive. Therefore, compared with the increase in freeze-thaw cycles, the reduction in freeze-thaw cycles weakened the physiological sensitivity of S. caninervis to snow depth changes.

Strain Y74(T)was an isolate from the sandy soil in the town of Huatugou, Qinghai-Tibet Plateau, China. An analysis of this strain's phenotypic, chemotaxonomic, and genomic characteristics established the relationship of the isolate with the genusPlanococcus. Strain Y74(T)was able to grow between 4 and 42 degrees C (with an optimum temperature of 28 degrees C) at pH values of 6-8.5 and in 0%-7% (w/v) NaCl. The dominant quinones were MK-8 and MK-7. The polar lipids were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, and an unknown phospholipid. The majority of the fatty acid content was anteiso-C-15:0(28.8%) followed by C-16:1 omega 7c alcohol (20.9%) and iso-C-14:0(13.4%). The 16S rRNA gene sequence similarity analysis demonstrated a stable branch formed by strain Y74(T)andPlanococcus halotoleransSCU63(T)(99.66%). The digital DNA-DNA hybridization between these two strains was 57.2%. The G + C content in the DNA of Y74(T)was 44.5 mol%. In addition, the morphological, physiological, and chemotaxonomic pattern clearly differentiated the isolates from their known relatives. In conclusion, the strain Y74(T)(=JCM 32826(T) = CICC24461(T)) represents a novel member of the genusPlanococcus,for which the namePlanococcus antioxidanssp. nov. is proposed. Strain Y74(T)was found to have potent antioxidant activity via its hydrogen peroxide tolerance and its 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging activity. The DPPH radical-scavenging activity was determined to be 40.2 +/- 0.7%. The genomic analysis indicated that six peroxidases genes, one superoxide dismutase gene, and one dprA (DNA-protecting protein) are present in the genome of Y74(T).