Selenium-oxidizing Agrobacterium sp. T3F4 steadily colonizes in soil promoting selenium uptake by pak choi (Brassica campestris).

Selenium (Se) deficiency in soil is linked to its low content in edible crops, resulting in adverse impacts on the health of 15% of the global population. The crop mainly absorbs oxidized selenate and selenite from soil, then converts them into organic Se. However, the role of Se-oxidizing bacteria in soil Se oxidation, Se bioavailability and Se absorption into plants remains unclear. The strain Agrobacterium sp. T3F4, isolated from seleniferous soil, was able to oxidize elemental Se into selenite under pure culture conditions. The green fluorescent protein (gfp)-gene-marked strain (T3F4-GFP) and elemental Se or selenite (5 mg·kg-1) were added to pak choi (Brassica campestris ssp. chinensis) pot cultures. Observation of the fluorescence and viable counting indicated that GFP-expressing bacterial cells steadily colonized the soil in the pots and the leaves of the pak choi, reaching up to 6.6 × 106 and 2.0 × 105 CFU g-1 at 21 days post cultivation, respectively. Moreover, the total Se content (mostly organic Se) was significantly increased in the pak choi under T3F4 inoculated pot culture, with elemental Se(0) being oxidized into Se(IV), and soil Se(IV) being dissolved before being absorbed by the crop. After strain T3F4 was inoculated, no significant differences in microbial diversity were observed in the soils and roots, whereas the abundance of Rhizobium spp. was significantly increased. To our knowledge, this is the first time that Se-oxidizing Agrobacterium sp. T3F4 has been found to steadily colonize soil and plant tissues, and that its addition to soil increases the absorption of Se in plants. This study provides a potential strategy for Se biofortification.

Sphingomonas gilva sp. nov., isolated from mountain soil.

A Gram-stain-negative, strictly aerobic, motile, yellow, rod-shaped bacterium, designated ZDH117T, was isolated from soilsampled atthe Danxialandformin Guangdong Province, PR China. The 16S rRNA gene sequence of strain ZDH117T had highest similarityvalues to Sphingomonas adhaesivaDSM 7418T (97.5 %), SphingomonasdesiccabilisCP1DT (97.3 %) and Sphingomonas ginsenosidimutans KACC 14949T (97.2 %). However, phylogenetic analyses based on 16S rRNA gene sequences demonstrated that strain ZDH117T clustered with Sphingomonas zeicaulis 541T (96.17 %) and Sphingomonas sanxanigenens DSM 19645T (95.95 %). The genomic average nucleotide identity values of ZDH117T with S. adhaesiva DSM 7418T, S. desiccabilis CP1DTand S. ginsenosidimutans KACC TT were 75.1, 75.2 and 75.0 %, respectively. The G+C content of the genomic DNA was 67.6 mol%. Strain ZDH117T was characterized to have ubiquinone-10 as the predominant respiratory quinone, sym-homospermidine as the major polyamine and summed feature 8 (C18 : 1ω6c and/or C18 : 1ω7c), C14 : 0-2OH, C16 : 0 and summed feature 3 (C16 : 1ω6c and/or C16 : 1ω7c) as the major cellular fatty acids (>5 % of total). The predominant polar lipids were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylcholine, sphingoglycolipid, an unidentified phospholipid and three unidentified lipids. On the basis of its phenotypic, chemotaxonomic and phylogenetic characteristics, strain ZDH117T represents a novel species of the genus Sphingomonas, for which the name Sphingomonas gilva sp. nov. is proposed. The type strain is ZDH117T (=KCTC 62894T=CCTCCAB 2018262T).

Sphingomonas aracearum sp. nov., isolated from rhizospheric soil of Araceae plants.

A Gram-stain-negative, single polar flagellum bacterium, WZY27T, was isolated from rhizospheric soil of Araceae plants. The results of phylogenetic analysis based on 16S rRNA gene sequences showed that this strain is closely related to Sphingomonas adhaesiva DSM 7418T (97.2 % similarity), Sphingomonaskoreensis KCTC 2883 (97.1 %) and Sphingomonas ginsenosidimutans JCM 17074T (97.0 %). The genomic average nucleotide identity values between strain WZY27T and the above three strains were 75.3, 73.2 and 75.4 %, and the in silico DNA-DNA hybridization values were 19.1 , 20.1 and 20.9 %, respectively. The major fatty acids (>5 %) of strain WZY27T were summed feature 8 (C18 : 1 ω7c/C18 : 1 ω6c), C16 : 0, C14 : 0 2-OH and C18 : 1 ω7c 11-methyl. The predominant respiratory quinone and polyamine were ubiquinone Q-10 and homospermidine, respectively. The polar lipids were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, phospholipids, glycolipids, phosphatidylcholine and sphingoglycolipid. The G+C content of the genomic DNA was 68.4 mol%. Based on the results of genotypic, chemotaxonomic and phenotypic characterization, strain WZY27T represents a novel species of the genus Sphingomonas, for which the name Sphingomonas aracearum sp. nov. is proposed. The type strain is WZY27T (=KCTC 62523T=CCTCC AB 2018056T).

[Advance in studies on pharmacological effect of salidroside on nervous system diseases].

Salidroside is an extract from Rhodiola crenulata as well as one of major active constituents. In studies of recent years, salidroside showed multiple effects in protecting nerves, scavenging free radicals, regulating central nervous system neurotransmitter, increasing the ability to promote nerve repair and modulating of apoptosis-related gene expression. Hence, it is expected to be applied in treating degenerative nerve diseases and brain ischemic diseases. This essay summarizes studies on pharmacological effects of salidroside on nerve system diseases, providing reference for further studies, development and application of R. crenulata.