The Composition and Diversity of the Rhizosphere Bacterial Community of Ammodendron bifolium Growing in the Takeermohuer Desert Are Different from Those in the Nonrhizosphere.

Soil microorganisms play important roles in vegetation establishment and soil biogeochemical cycling. Ammodendron bifolium is a dominant sand-fixing (i.e., stabilizing sand dunes) and endangered plant in the Takeermohuer Desert, and the bacterial community associated with this plant rhizosphere is still unclear. In this study, we investigated the composition and diversity of the bacterial community from the A. bifolium rhizosphere and bulk soil at different soil depths (i.e., 0-40 cm, 40-80 cm, 80-120 cm) using culture and high-throughput sequencing methods. We preliminarily analyzed the edaphic factors influencing the structure of bacterial communities. The results showed that the high-salinity Takeermohuer Desert has an oligotrophic environment, while the A. bifolium rhizosphere exhibited a relatively nutrient-rich environment due to higher contents of soil organic matter (SOM) and soil alkaline nitrogen (SAN) than bulk soil. The dominant bacterial groups in the desert were Actinobacteria (39.8%), Proteobacteria (17.4%), Acidobacteria (10.2%), Bacteroidetes (6.3%), Firmicutes (6.3%), Chloroflexi (5.6%), and Planctomycetes (5.0%) at the phylum level. However, the relative abundances of Proteobacteria (20.2%) and Planctomycetes (6.1%) were higher in the rhizosphere, and those of Firmicutes (9.8%) and Chloroflexi (6.9%) were relatively higher in barren bulk soil. A large number of Actinobacteria were detected in all soil samples, of which the most abundant genera were Streptomyces (5.4%) and Actinomadura (8.2%) in the bulk soil and rhizosphere, respectively. The Chao1 and PD_whole_tree indices in the rhizosphere soil were significantly higher than those in the bulk soil at the same soil depth and tended to decrease with increasing soil depth. Co-occurrence network analyses showed that the keystone species in the Takeermohuer Desert were the phyla Actinobacteria, Acidobacteria, Proteobacteria, and Chloroflexi. Furthermore, the major edaphic factors affecting the rhizosphere bacterial community were electrical conductivity (EC), SOM, soil total nitrogen (STN), SAN, and soil available potassium (SAK), while the major edaphic factors affecting the bacterial community in bulk soil were distance and ratio of carbon to nitrogen (C/N). We concluded that the A. bifolium rhizosphere bacterial community is different from that of the nonrhizosphere in composition, structure, diversity, and driving factors, which may improve our understanding of the relationship between plant and bacterial communities and lay a theoretical foundation for A. bifolium species conservation in desert ecosystems.

Pontibacter kalidii sp. nov., isolated from rhizosphere soil of Kalidium foliatum.

A Gram-negative, aerobic, gliding motile, rod-shaped bacterium, designated XAAS-72T, was isolated from the rhizosphere soil of Kalidium foliatum sampled in the Xinjiang Uyghur Autonomous Region, PR China. Cells grew at 4-45 °C, pH 5.0-8.0 and 0-8% NaCl, with optimal growth at 20-30 °C, pH 6.0-7.0 and 1-2 % NaCl. Strain XAAS-72T is closely related to members of the genus Pontibacter, namely Pontibacter korlensis CCTCC AB 206081T (97.6%) and Pontibacter flavimaris ACCC 19859T (97.2 %), and <94.6 % related to other currently described Pontibacter strains. The average nucleotide identity values between XAAS-72T and P. korlensis CCTCC AB 206081T and P. flavimaris ACCC 19859T were 77.9 and 86.9 %, respectively; the corresponding digital DNA-DNA hybridization values were 21.7 and 31.8 %. Menaquinone-7 was the predominant respiratory menaquinone. The polar lipids consisted of phosphatidylethanolamine, two unidentified aminophospholipids, two unidentified glycolipids and five unidentified lipids. The major cellular fatty acids were summed feature 4 (containing iso-C17 : 1 I/anteiso-C17 : 1 B), summed feature 3 (containing C16 : 1 ω7c/C16 : 1 ω6c) and iso-C15 : 0. The genome length of strain XAAS-72T was 5 054 860 bp with a genomic DNA G+C content of 54.5 mol%. The phenotypic and genotypic data suggest that strain XAAS-72T represents a novel species of the genus Pontibacter, for which the name Pontibacter kalidii sp. nov. is proposed. The strain is XAAS-72T (CGMCC 16594T=KCTC 72095T).

Composition and Distribution Characteristics of Rhizosphere Bacterial Community of Ammodendron bifolium Growing in Takeermohuer Desert Are Different from Those in Non-rhizosphere.

Soil microorganisms play important roles in vegetation establishment and soil biogeochemical cycling. Ammodendron bifolium is a dominant sand-fixing and endangered plant in Takeermohuer Desert, and bacterial community associated with this plant rhizosphere is still unclear. In this study, we studied the composition and diversity of bacterial community from A. bifolium rhizosphere and bulk soil at different soil depths (i.e., 0-40 cm, 40-80 cm, 80-120 cm) using traditional bacterial isolation and high-throughput sequencing approaches, and preliminarily analyzed the edaphic factors influencing the structure of bacterial communities. Results showed that Takeermohuer Desert with high salinity has been an oligotrophic environment, while the rhizosphere exhibited eutrophication resulting from high content SOM (soil organic matter) and SAN (soil alkaline nitrogen) compared with bulk soil. The dominant bacterial groups in the desert were Actinobacteria (39.8%), Proteobacteria (17.4%), Acidobacteria (10.2%), Bacteroidetes (6.3%), Firmicutes (6.3%), Chloroflexi (5.6%), and Planctomycetes (5.0%) at the phyla level. However, the relative abundances of Proteobacteria (20.2%) and Planctomycetes (6.1%) were higher in eutrophic rhizosphere, and Firmicutes (9.8%) and Chloroflexi (6.9%) relatively higher in barren bulk soil. A large number of Actinobacteria were detected in all soil samples, of which the most abundant genus was Streptomyces (5.4%) and Actinomadura (8.2%) in the bulk soil and rhizosphere, respectively. The Chao1 and PD indexes in rhizosphere were significantly higher than those in bulk soil at the same soil depth, and tended to decrease with increasing soil depth. Co-occurrence network analyses showed that the keystone species in Takeermohuer Desert were Actinobacteria, Acidobacteria, Proteobacteria, and Chlorofexi. Furthermore, the major environmental factors affecting rhizosphere bacterial community were EC (electrical conductivity), SOM, STN (soil total nitrogen), SAN, and SAK (soil available potassium), while bulk soil were distance and C/N (STC/STN). We concluded that A. bifolium rhizosphere bacterial community is different from non-rhizosphere in composition, distribution, and environmental influencing factors, which will have important significances for understanding their ecological functions and maintaining biodiversity.

Comparison of Pharmacokinetics and Tissue Distribution Characteristics of Three Diterpenoid Esters in Crude and Prepared Semen Euphorbiae.

BACKGROUND: Semen Euphorbiae (SE) and Semen Euphorbiae Pulveratum (SEP) have a long history of medicinal use. SEP is the processed product of SE; both ancient and modern studies have shown that SEP has a lower toxicity compared to SE. To clarify the influence of processing on the pharmacological properties of SE and SEP, a study was carried out to compare the pharmacokinetics and distribution characteristics of three active compounds after oral administration of SE and SEP extracts. METHODS: A UPLC-MS/MS method was established to simultaneously determine the contents of Euphorbia factors L1, L2, and L3 in rat plasma and mouse tissues after an oral administration of crude and processed SE with approximately the same dosage. Plasma and heart, liver, spleen, lung, kidney, and colon tissue samples were treated with ethyl acetate and separated by gradient elution on a C18 column with a mobile phase of 0.1% formic acid and methanol. RESULTS: The established method had good selectivity, linear range, accuracy, precision, stability, matrix effect, and extraction recovery. The area under the concentration time curve, time to maximum concentration, maximum concentration, half-life of elimination, and mean retention time of plasma samples in SEP-treated group decreased, and the clearance in SEP-treated group increased. Moreover, the active component concentrations in colon, liver, and kidney tissues were more followed by those in the heart, lungs, and spleen. CONCLUSION: These results indicate that the processing could influence the pharmacokinetics and tissue distribution of Euphorbia factors L1, L2, and L3 after oral administration of crude and processed SE. The data obtained may lay a foundation for the clinical use of SE and for further study on the processing mechanism of SE.

[Estimation of tissue's blood oxygen parameters from visible absorption spectrum of tissues by artificial neural network].

Total hemoglobin concentration (THC) and hemoglobin oxygen saturation (SO2) are essential parameters to doctors who wonder patients' hematogenous conditions and oxygen supplies and consumptions. Instruments presently used for measuring these parameters have big size of detecting probes that limit their applications to inner bodies. An optical probe involving two fibers with source-detector separations of one hundred micrometers was developed in the present study for purpose of minimally invasive inner detecting, which uses steady-state, broadband (300-1 000 nm) light source. The source light is delivered to targets through one fiber and the reflected light from the targets is collected and transferred to a spectrometer through the other fiber. Reflectance spectrum is obtained from the spectrometer. The method of reading THC and SO2 from the reflectance spectrum was developed using liquid-tissue phantoms containing intralipid and blood. Firstly, reflex spectrum of intralipid was recorded before mixtures of intralipid and blood with different THC were made as tissue phantoms. Then the fiber optical spectrometer was used to obtain reflex spectra as the phantoms' SO2 changed; simultaneously their corresponding THC and SO2 were recorded as the scale values by an oximeter. Differences of reflex spectra in 520-590 nm between intralipid and tissue models were proved reliably. Secondly, after data collections of absorption spectra and scale values were finished, two artificial neural networks (ANN) were build to model the relationship between scale values and absorption spectra. After being trained, the ANNs could output THC and SO2 correctly when an absorption spectrum was input. The ANNs produced errors of less than 4 micromol x L(-1) for THC and 5% for SO2. In vivo and minimally invasive measurements of THC and SO2 of brain tissues in different depth were finished on 30 rats by this specific system with the ANNs. The probe was inserted stereotactically to a depth of 6 mm with measurements obtained every 0.2 mm. SO2 of gray mater and white mater of rats was respectively obtained as 0.60-0.70 and 0.45-0.55. The highest THC, 110 micromol x L(-1) was measured around rat cortex. THC of brain tissue in other depth is 70-90 micromol x L(-1). These values agree well with reported data. This simple, inexpensive method deserves further study to establish its efficacy for THC and SO2 measurements of inner body.

[Comparison of antitumor efficacy between arsacetyl and arsenic trioxide in vitro].

BACKGROUND & OBJECTIVE: Recently, it was reported that some organic arsenics was stronger than inorganic arsenics in inducing carcinoma cell apoptosis. This study was designed to compare arsacetyl (ASAC), a kind of organic arsenics, with As2O3 in the effect of inhibiting proliferation and inducing apoptosis in carcinoma cells. METHODS: MTT (Methythiazolyl tetrazolium) assay and analysis of apoptosis were used to evaluate the effects of arsacetyl and As2O3 on the proliferation of SMMC-7721 and their mechanisms. Their toxicity to vessel endothelium cells (VECs) was also determined by using MTT method. RESULTS: Both As2O3 and arsacetyl significantly inhibited the proliferation of SMMC-7721, the inhibitory effect was dose- and time-dependent and arsacetyl was stronger than As2O3 [e.g. inhibitory ratio: (14.2 +/- 1.5)%, treated with 0.1 mumol/L arsacetyl for 48 h; (27.1 +/- 3.0)%, treated with 0.1 mumol/L arsacetyl for 48 h]. 1 mumol/L As2O3 and 0.1 mumol/L arsacetyl almost had no toxicity to VEC, while they induced SMMC-7721 apoptosis indicated morphologically by "small apoptopic body" formation; DNA ladders appeared on agarose gel electrophoresis. The flow cytometry assay indicated that most of the cells were arrested in S + G2/M phase and the apoptotic peak appeared. CONCLUSION: The ability of arsacetyl inducing apoptosis was stronger than As2O3, and SMMC-7721 in the G0/G1 phase may be the target of drug action.