Interguild fungal competition in litter and soil inversely modulate microbial necromass accumulation during Loess Plateau forest succession.

Microbial interactions determine ecosystem carbon (C) and nutrient cycling, yet it remains unclear how interguild fungal interactions modulate microbial residue contribution to soil C pools (SOC) during forest succession. Here, we present a region-wide investigation of the relative dominance of saprophytic versus symbiotic fungi in litter and soil compartments, exploring their linkages to soil microbial residue pools and potential drivers along a chronosequence of secondary Chinese pine (Pinus tabulaeformis) forests on the Loess Plateau. Despite minor changes in C and nitrogen (N) stocks in the litter or soil layers across successional stages, we found significantly lower soil phosphorus (P) stocks, higher ratios of soil C: N, soil N: P and soil C: P but lower ratios of litter C: N and litter C: P in old (>75 years) than young stands (<30 years). Pine stand development altered the saprotroph: symbiotroph ratios of fungal communities to favor the soil symbiotrophs versus the litter saprotrophs. The dominance of saprotrophs in litter is positively related to microbial necromass contribution to SOC, which is negatively related to the dominance of symbiotrophs in soils. Antagonistic interguild fungal competition in litter and soil layers, in conjunction with increased fungal but decreased bacterial necromass contribution to SOC, jointly contribute to unchanged total necromass contribution to SOC with stand development. The saprotroph: symbiotroph ratios in litter and soil layers are mainly driven by soil P stocks and stand parameters (e.g., stand age and slope), respectively, while substrate stoichiometries primarily regulate microbial necromass accumulation and fungal: bacterial necromass ratios. These results provide novel insights into how microbial interactions at local spatial scales modulate temporal changes in SOC pools, with management implications for mitigating regional land degradation.

Ceriporia lacerata HG2011 enhances P mobilization and wheat agronomic performance irrespective of P fertilization levels.

AIMS: To identify soil phosphorus (P) mobilization and wheat agronomic performance in response to the P mobilizer Ceriporia lacerata HG2011 could provide a new strategy for improving fertilizer P efficiency in wheat cultivation. METHODS AND RESULTS: Liquid culture showed that C. lacerata HG2011 converted Ca3 (PO4 )2 , FePO4 , AlPO4 , phytate, lecithin and ribonucleic acid into soluble inorganic P, which was stimulated by ammonium and urea but less influenced by P supply. In the incubation experiment, this fungus colonized on wheat roots, and mobilized P in the soils regardless of Olsen P levels. The efflux of protons, organic acids and phosphatase could be involved in insoluble P mobilization. In the greenhouse pot experiment, C. lacerata HG2011 increased soil Olsen P under different P fertilization levels, improved wheat P uptake by 15.39%-28.70%, P fertilizer use efficiency by 4.26%-13.04% and grain yield by 12.24%-22.39%. CONCLUSIONS: Ceriporia lacerata HG2011 was able to colonize on wheat roots, mobilize P in soils and improve wheat agronomic performance irrespective of P fertilization levels. SIGNIFICANCE AND IMPACT OF THE STUDY: Ceriporia lacerata HG2011 could be used to enhance the quality of compost or as a bio-fertilizer for P mobilization in modern sustainable agriculture.

Protective Effects of Zinc on Salmonella Invasion, Intestinal Morphology and Immune Response of Young Pigeons Infected with Salmonella enterica Serovar Typhimurium.

The study aimed to determine the effects of orally supplemental zinc on body weight, Salmonella invasion, serum IgA, intestinal histomorphology, and immune response of Salmonella enterica serovar Typhimurium (S. typhimurium)-challenged young pigeons. A total of 72 healthy White King pigeons (25 days old) with similar weight were randomly assigned to 3 treatments with six replicate cages. The 3 treatments were unchallenged, S. typhimurium-challenged, and S. typhimurium-challenged orally supplemented with 1 mg zinc per bird. Salmonella infection decreased (P < 0.05) the body weight, the bursa index, the serum IgA content, and the villus height/crypt depth ratio in the ileum, but increased the neutrophil proportion (P < 0.001) and the mRNA expressions of IL-1ß and IL-8 in the jejunum (P < 0.05). Orally supplemental zinc reduced (P = 0.007) the bacterial load in the liver and improved (P < 0.05) the body weight, the bursa index, the serum IgA content, the villus height/crypt depth ratio, and the NOD-like receptor family pyrin domain containing 3 (NLRP3) protein expression, as well as tended to increase (P = 0.064) the protein abundance of caspase-1 of the jejunum, but did not alleviate the high level of neutrophil proportion and IL-1ß mRNA expression of the jejunum (P > 0.05). The results indicated that oral zinc supplementation improved the intestinal mucosal morphology and enhanced the immune response, as well as activated caspase-1-dependent cell pyroptosis pathways in the jejunal epithelium, thereby restricting Salmonella invasion of the challenged young pigeons.

Phosphorus mobilization and improvement of crop agronomic performances by a new white-rot fungus Ceriporia lacerata HG2011.

BACKGROUND: Some soil microorganisms can mobilize unavailable phosphorus (P) in soils for plant use and increase P fertilizer efficiency. Thus, an abiotic P solubilization experiment and fungal incubation in solution and soil were conducted to investigate the mobilization of various P compounds by a new white-rot fungus Ceriporia lacerata HG2011. The crop agronomic performances were then evaluated in the winter barley-summer maize-winter wheat rotation field. RESULTS: Ceriporia lacerata HG2011 had a wide P mobilization spectrum and mobilized P by different mechanisms depending on P sources supplied in liquid culture. The chief mechanism employed by this fungus was the production of protons in mobilizing Ca3 (PO4 )2 , low-molecular-weight organic acids and other unknown substances in FePO4 and AlPO4 , phytase (an inducible enzyme in the presence of phytate) in phytate, and phosphatase in lecithin and ribonucleic acid, respectively. As a result of the large fungal biomass, P accumulated in the hypha should also be considered in the assessment of the fungal P mobilization, and not just only soluble inorganic P. As C. lacerata HG2011 colonized on and in the test soil, phosphatase and phytase activities were enhanced but pH decreased in the soil, leading to P mobilization. The application of this fungus mobilized soil P, increased crop P uptake and yields, and consecutively reduced P fertilizer use without yield sacrifices in the multiple crop rotation field. CONCLUSION: C. lacerata HG2011 showed a new use with respect to mobilizing soil P and reducing P fertilizer input in modern agriculture beyond medical purposes, environmental protection and biofuel production. © 2021 Society of Chemical Industry.

New Functions of Ceriporia lacerata HG2011: Mobilization of Soil Nitrogen and Phosphorus and Enhancement of Yield and Quality of Ketchup-Processing Tomato.

The overuse of chemical nitrogen (N) and phosphorus (P) fertilizers in tomato cultivation is common for high fruit yields to meet the ever-increasing industrial needs, resulting in poor fruit quality, fertilizer waste, and environmental pollution. Nutrient-mobilizing microbes increase soil nutrient supply and decrease fertilizer use without yield sacrifices. Thus, the influence of a new white-rot fungus Ceriporia lacerata HG2011 was studied on soil N and P mobilization in lab and ketchup tomato performances in field. Compared with noninoculation, soil pH decreased, while ammonia (NH4+-N), available P, microbial biomass N and P, and activities of protease and phosphatase in the inoculated soil increased as the fungus grew on and in the sterile soil. Protease activity was positively correlated with NH4+-N and phosphatase activity was with water-soluble P and Olsen P in the sterile soil. Soil pH showed an inverse correlation with available P. In the field experiment, the treatments included a blank control, C. lacerata, chemical fertilizers, and chemical fertilizers plus C. lacerata. Fungal inoculation enhanced the available N and P and the activities of protease and phosphatase in both fertilized and unfertilized soils, leading to the increment of plant nutrient uptake. Fungal application increased the fruit yield by 18.18-20.16%, soluble solids by 3.17-6.30%, soluble sugar by 10.67-43.33%, sugar-acid ratio 20.19-52.91%, and vitamin C by 8.83-34.90%. Therefore, our results first demonstrated the new functions of C. lacerata HG2011 in the mobilization of soil N and P and the improvement of plant nutrient uptake, yield, and quality, showing a potential use as biofertilizers in ketchup-processing tomato cultivation.

[Effect of different fertilization treatments on growth,secondary metabolites,and seed yield and quality of Perilla frutescens].

Perilla frutescens,an annual plant in Labiatae family,is grown throughout China and can be used for medicine purposes and as food additives. The present field experiment was carried out to study the effects of different fertilizer treatments on the concentrations and accumulations of antioxidant components,including flavonoids and polyphenols,growth,seed yields and qualities of this plant.The main aim of this study is to provide farmers some advice for improving the yields and qualities of P. frutescens in theory and practice.Five treatments were set up,including a no fertilizer control(CK),chemical fertilizers(CF),organic fertilizers(M),organic fertilizers plus chemical fertilizers at the rates of 1 ∶1 and 1 ∶3 in terms of nitrogen(50 M,25 M). Plant growth parameters were recorded and total flavonoids and polyphenols were determined in three key growth stages of P. frutescens. At the fast growth period,samples of roots,leaves,and stems were collected for determining a total of flavonoids and polyphenols as well as DPPH removal rate of ethanol extracts. Seed yields and qualities were also recorded at harvest. The results showed fertilization enhanced growth and seed yields although no significant difference was observed in growth and seed yields in inorganic-organic fertilizer treatments. The total flavonoids,polyphenols,and DPPH removal rate of ethanol extracts followed the sequence leaves>stems>roots,indicating synthesis of these metabolites in the leaves. DPPH removal rate showed a positive linear correlation with total flavonoid and polyphenol concentrations. In addition,organic-inorganic fertilization significantly increased the numbers of both effective panicles and paniclegrains. Fertilizer treatments had no effect on seed qualities of P. frutescens,while 50 M achieved the highest yield,which increased by 14. 73% compared to CF alone. In general,50 M increased antioxidant components,biomass,and seed yield of P. frutescens,meriting advocate in cultivation.

Negative effects of artemisinin on phosphorus solubilizing bacteria in vitro.

The anti-malarial drug artemisinin is extracted from the leaves of Artemisia annua L. Due to toxicity to some microorganisms, the release of artemisinin from this medicinal plant in commercial cultivation might produce a potential risk for phosphorus (P) solubilizing bacteria (PSB). Therefore, the growth, P mobilization, and proton and organic acid efflux by two PSB isolates, Bacillus subtilis and Pseudomonas fluorescens, obtained from the soil without growing A. annua L. in history in the region for growing A. annua L., Chongqing, China, were studied through soil and solution incubations with different nominal concentrations of artemisinin (0, 2.5, 5.0, and 10.0 mg/kg or mg/L). Addition of artemisinin into soil and culture solutions decreased significantly the number of PSB except P. fluorescens at a low artemisinin concentration (2.5 mg/L) in culture solution which remained unchanged in comparison with the control (without artemisinin). This suggests high artemisinin inhibited the cell division or led to the death of PSB, and the different species responded differently to artemisinin. Compared with original soil, PSB inoculation significantly increased Olsen P, whilst the addition of artemisinin decreased this P form in soil. There was a positive correlation between the number of PSB and Olsen P content in soils (r2 = 0.824, n = 8), indicating the involvement of PSB in P mobilization of insoluble minerals. Oxalate and acetate were commonly found in the bacterial culture solutions, which accounted for 73.6-84.4% of all organic acids in the culture medium without artemisinin. Malate was detected in the culture solution of B. subtilis, and citrate and succinate in P. fluorescens. The percentage of tricalcium phosphate solubilization (PTPS) positively correlated to the concentrations of protons and all organic acids (r2proton＝0.901, n＝8, P＜0.01; r2organic acids＝0.923, n＝8, P＜0.01). The concentrations of protons, organic acids and soluble inorganic P in culture solutions, and PTPS were decreased simultaneously as nominal artemisinin concentrations increased. For these decreases it implies the metabolic inhibition and the death of PSB caused by artemisinin could be the main reasons for the less efflux of protons and organic acids, presumably resulting in the decreased ability of PSB to mobilize inorganic P. Therefore, artemisinin released from A. annua L. in commercial and continual cultivation could adversely affect the community structure and inorganic P mobilization of PSB in soils.

[Influence of continuous cropping on growth of Artemisia annua and bacterial communities in soil].

In this study, several types of Artemisia annua in soil, including the soil which had not been planted, or planted for one year, or continuously planted for three or five years were collected, in order to study the influences of continuous cropping on the growth of A. annua, content of artemisinin, available nutrient of soil, and bacterial community structure through adopting routine analysis and Illumina MiSeq high-throughput sequencing. The results showed that continuous cropping inhibited significantly the growth of A. annua and reduced leaf biomass, content and yield of artemisinin, with the maximum decreasing amplitude of 30.20%, 7.70% and 35.58% respectively. The content of soil organic matter, available nitrogen, available phosphorus and 16S rRNA sequence number were increased to different extents after continuous cropping of A. annua. According to the results of high-throughput sequencing, 634-812 types of common bacteria belonged to 21 categories were planted in different soil of A. annua with different planting years, which represented that the distribution distance of the point of bacterial community with different years among coordinate system of principal component was relative distant, and community structure had significant changes (P<0.05). As the planting years increased, the abundance of Actinobacteria, Chloroflexi, Gemmatimonadetes decreased in contrast to Proteobacteria, Acidobacteria and Verrucomicrobia. In the top 20 types of predominant bacteria,Nitrospira japonica and Nitrospira disappeared, among which, only Gemmatimonadaceae, Micromonosporaceae, Nitrosomonadaceae, Xanthobacteraceae, and unculture bacterium JG30-KF-AS9 were similar, indicating that the planting and continuous cropping of A. annua selectively inhibited the growth and reproduction of soil bacteria, and influenced the supply and transform of soil nutrient, leading to a poor growth and resulting in reduction of artemisinin content and yield. Therefore, it is necessary to advocate crop rotation in the process of planting A. annua.

[Effect of phosphorus supply and signal inhibitors on oxalate efflux in ectomycorrhizal fungi].

OBJECTIVE: Phosphorous (P) is one of the essential elements for tree growth in forests. It is beneficial to characterize oxalate secretion by ectomycorrhizal fungi in response to P supply for understanding the mechanism of P mobilization in soils. METHOD: In the present experiment, the influence of P supplies and inhibitors of Ca2+ signal/anion channel on oxalate efflux in ectomycorrhizal fungi was studied in the pure liquid culture with various P concentrations. RESULTS: Ectomycorrhizal fungi released a large amount of H+ and organic acids such as oxalate, acetate, malate, citrate and succinate, which are important for mobilization of insoluble P in the soils. Oxalate accounted for 15. 14% to 36. 01% of the total organic acids released by the fungi and was accelerated in culture solution under the condition of low P supply, but inhibited under normal and high P. CONCLUSION: Ectomycorrhizal fungi released a large amount of H+ and organic acids, particularly oxalate, which might be beneficial to inorganic P mobilization in the soils and improvement of P nutrition for their host plants.

Salidroside prevents cognitive impairment induced by chronic cerebral hypoperfusion in rats.

OBJECTIVE: To investigate the effects of salidroside on cognitive dysfunction induced by chronic cerebral hypoperfusion in rats. METHODS: Male Sprague-Dawley rats (n = 36) were divided into three groups (n = 12 per group): sham operation; bilateral permanent occlusion of the common carotid arteries (2-VO); 2-VO + salidroside. Rats received 20 mg/kg per day salidroside or vehicle intraperitoneal injection beginning the day before surgery and continuing until 34 days postoperatively. Cognitive function was evaluated by Morris water maze test and hippocampal long-term potentiation (LTP) measurement. Hippocampal neuronal apoptosis was evaluated via immunofluorescence. RESULTS: Chronic cerebral hypoperfusion caused marked cognitive deficit and LTP inhibition. These effects were largely ameliorated by salidroside administration. Salidroside prevented caspase-3 activation, increased the ratio of Bax/Bcl-2, and reversed hippocampal neuronal loss induced by chronic cerebral hypoperfusion. CONCLUSIONS: Salidroside prevents cognitive deficits caused by chronic cerebral hypoperfusion in rats, and alleviates apoptosis in the hippocampal CA1 area.

[Response of ectomycorrhizal fungi to aluminum stress and low potassium soil].

Soil acidification, aluminum (Al3+) toxicity and nutrient deficiency could be some of the most important reasons for the decline and death of forests in tropical and subtropical areas. Ectomycorrhizal fungi for Al3+ resistance and nutrient mobilization are beneficial for preventing forests against Al3+ toxicity and increasing forest productivity. Therefore, Suillus luteus (SI 13), Pisolithus tinctorius (Pt 715) and Suillus subluteus (Ss 00) were grown in liquid culture medium with soil as the sole K source under Al3+ stress to study the fungal growth, organic acid and proton efflux, and potassium (K) unitization. The result indicated that the fungal growth, organic acid and proton efflux, and nutrient uptake, including nitrogen (N), phosphorus (P) and potassium (K), were regulated by Al3+ concentration in culture solutions. They increased with increasing Al3+ at low concentration and after reaching a peak, they started to decrease. Fungal strain with high resistance to Al3+ also showed higher Al3+ concentration at the peak than those with low ability. Al3+ concentration at the peak of fungal biomass and N uptake by Pt 715 was four folds or twice of Ss 00 and SI 13, respectively. The uptake of P and K and efflux of organic acids and protons by Pt 715 were also higher than Ss 00 and Sl 13. All three fungal strains could utilize structural K in soil minerals and the utilization rate reached 2.10% for Pt 715, 1.43% for Ss 00 and 1.17% for Sl 13, respectively, which could be related to the types and amount of organic acids and protons.

[Effect of fibrous root extract of Coptis chinensis on soil microbes and enzyme activities].

Coptis chinensis is widely used as Chinese medicine herbs and serious soil problems occur after continual cultivation of this medicinal plant. In the preset experiment, fibrous root extract of C. chinensis (REC) was added into soil to study the effect of REC on microbes and enzyme activity in soil. The results showed that both bacteria and actinomycetes decreased by about 2 times in contrast to fungi, which increased by about 3 folds. Phosphorus bacteria, potassium bacteria, azotobacter, ammonia bacteria, and nitrifying bacteria were also reduced significantly by REC, suggesting the inhibition of nitrogen biofixation and supply, mobilization of phosphorus and potassium, ad plant growth promotion as REC added into soil. There were multiple influences of REC on soil enzyme activities. Invertase activity was stimulated, while urease was inhibited and dehydrogenase unchanged by REC, indicating the interference of biochemical reactions in soil. In addition, type and total content of phosphorus lipid fatty acids (PLFAs) , the signature of microbes, decreased while the ratio of bacterium to fungus PLFAs increased as REC increased in soil, which suggested that fungi increased relatively with bacteria decreased thereby leading to easy occurrence of crop fungus diseases following cultivation of C. chinensis. The decrease in diversity and evenness indexes of microbial community in soil by REC indicated soil ecosystem deterioration and reduction of microbial groups and densities in soil. Therefore, allelopathic chemicals released from the roots of C. chinensis could change microbial community structure and resulted in serious soil problems by continual cropping of this medicinal plant.

Dual-delivery of vancomycin and icariin from an injectable calcium phosphate cement-release system for controlling infection and improving bone healing.

Infectious bone diseases following severely contaminated open fractures are frequently encountered in clinical practice. It is difficult to successfully repair bone and control infection at the same time. To identify a better treatment method, we prepared a dual-drug release system that was comprised of icariin (IC, a natural osteoinductive molecule), vancomycin (VA) and injectable calcium phosphate cement (CPC). The ultrastructure of the dual-drug release system was evaluated by scanning electron microscopy and the biocompatibility was assessed by cell culture. In addition, the release kinetics of IC and VA were respectively investigated by using high­performance liquid chromatography. Finally, this system was used to repair Staphylococcus aureus-contaminated bone defects in a rabbit model. Twelve weeks after the implantation of IC-VA/CPC, the contaminated bone defects were completely repaired, with significantly improved formation of lamellar bone and recanalization of the marrow cavity compared with the controls (CPC without antibiotics or osteoinductive agent). These results demonstrate that this dual-drug release system, with its concomitant antibiotic and osteoinductive properties, has significant potential for the treatment of contaminated bone injury or infectious bone disease.

[Effect of fertilization on phenolic components and antioxidant activities of Artemisia annua].

OBJECTIVE: A pot experiment with variable fertilizer treatments was carried out to study the influence of fertilization on the concentration and accumulation of polyphenols, scopoletin, chrysosplenol-D and chrysosplenetin in roots, stems and leaves and their antioxidant activities. The main aims were to fertilize scientifically in cultivation of Artemisia annua and improve the quality of the harvest organs. METHOD: These active components in leaves, stems and roots in the squaring stage were analyzed by HPLC and antioxidant activities of the extracts were evaluated by ultraviolet visible light colorimetric method. RESULT: The result showed the highest concentration of polyphenols, scopoletin, chrysosplenol-D and chrysosplenetin was in leaves, followed by stems and the lowest in roots. The antioxidant activities of the leaf extracts correlated positively with the concentrations of polyphenols, scopoletin, chrysosplenol-D and chrysosplenetin. Furthermore, fertilization promoted significantly the growth of A. annua, the biomass was increased by 57.37% (chemical fertilizer), 91.63% (mixture of chemical fertilizer and manure) and 92.27% (manure), respectively, compared to the blank control (without fertilizer). Fertilization, particularly mixture fertilization of chemical fertilizer and manure, increased generally the concentration and accumulation of polyphenols, scopoletin, chrysosplenol-D and chrysosplenetin as well as DPPH x scavenging ratio. CONCLUSION: Scopoletin, chrysosplenol-D and chrysosplenetin could be synthesized and stored mainly in leaves. The leaves might thus be the chief organ of A. annua for medical treatment. Finally, the mixture fertilization of chemical fertilizer and manure should be used to increase the yield and quality of A. annua.

[Allelopathic effect of artemisinin on green algae].

To study the growth effects of differing concentrations of artemisinin on green algae and to evaluate the ecological risk. The effects of artemisinin on the growth and the content change of chlorophyll, protein, oxygen, conductivity, SOD, CAT, MDA in Chlorella pyrenoidosa and Scenedesmus oblique were studied through 96 h toxicity tests. Artemisinin accelerated the growth of algae at a lower concentration ( <40 microg . L-1) with content increase of chlorophyll or protein and so on, and it inhibited the growth of algae at higher concentration ( >80 microg . L-1). The content of chlorophyll or protein in algae cells reduced with the increasing concentration of artemisinin, exhibiting the good concentration-effect relationship. SOD and CAT activity was stimulated at low concentrations ( <40 microg . L-1 ) and inhibited at high concentrations ( >80 microg . L- 1). However, MDA content increased significantly with the increase of concentration. According to the seven kinds of indicators changes, the time-response and dose-response suggested that the surfactant first hurt in Ch. pyrenoidosa was damaging membrane by changing membrane lipid molecules soluble. And primary mechanism on Chlorophyta cells might be related to the oxidation damage of lipid and other biological large molecules caused by artemisinin. The large-scale intensive planting of Artemisia annua may reduce the surrounding water productivity.

[Allelopathic effects of extracts from fibrous roots of Coptis chinensis on two leguminous species].

An experiment was carried out to study the allelopathic effects of Coptis chinensis fibrous root extracts (CRE) on the germination and seedling growth of Vicia faba and Pisum sativum in order to alleviate the allelopathic effects and increase land productivity. The seeds of both garden pea (P. sativum) and broad been (V. faba) were germinated in CRE solution of various concentrations, the germination rate, seedling growth and related physiological indexes were measured. The result indicated that there were no significant effects of CRE in low concentrations on seed germination, including both the rate and index, and seed vitality and membrane permeability. With the increment of CRE concentrations, however, the high seed membrane permeability and germination inhibition were observed. For example, the germination rates were reduced by 23.4% (P. sativum) and 9.5% (V. faba), respectively, in CRE solution with 800 mg . L-1. Simultaneously, soluble sugars and the free amino acids in the seeds were lower than those in the control (without CRE) after soaking seeds in CRE solutions. In addition, the seedling growth and nitrate reductase activity were stimulated by CRE at low concentrations in contrast to high concentrations which behaved otherwise and inhibited the nutrient utilization in endosperm. Therefore, the large amount of allelochemicals released from the roots and remains of C. chinensis in soils could inhibit the seed germination and seedling growth of legumes, which may lead to decrease even fail crop yields after growing this medical plant.

Molecular dynamics simulations of end-tethered single-stranded DNA probes on a silica surface.

The structure of DNA molecules tethered to surfaces may significantly affect the efficiency of hybridization on the DNA microarray. Understanding the structure of single-stranded DNA (ssDNA) tethered to surfaces is critical for applying the molecular recognition function of DNA microarrays. Although a number of experimental methods have been applied to determine the structure of the DNA probe on surfaces, they can not provide enough information on the dynamical behavior of the ssDNAs on surfaces. Herein, we investigated the dynamics and interaction of seven DNA probes tethered on a silica surface by a molecular dynamics simulation. From the simulation results, we examined the structure and dynamics of the ssDNAs, by calculating the root-mean-square derivations, the tilt angles, the radius of gyration, and the distances of the neighboring ssDNAs. The data obtained from our simulation suggests the packing density has a significant effect on the overall structure and molecular orientation change of surface-tethered ssDNAs, which is complementary to the recent experimental reports. Our simulation provided a structural insight, which is helpful to better understand the behavior of ssDNA on surfaces and optimize the design of DNA microarray.

[Studies on allelopathic effect of artemisinin on rhizobium].

Two strains of bean rhizobia, Rhizobium vigna 01 (slow-growing Rhizobium) and Rh. vigna 03 (fast-growing Rhizobium), were adopted to study allelopathic effect of artemisinin on the rhizobia. The results showed a significant inhibition of the reproduction and growth of rhizobium by artemisinin. After about 8 hours by adding 40 mg x L(-1) artemisinin into the culture medium, the number of rhizobia was less than half of those in normal culture. The utilization of sucrose and glucose by rhizobia decreased significantly as the concentration of artemisinin increased in the culture medium, which could be one of the main reasons for the inhibition of reproduction and growth of rhizobia by artemisinin. In addition, the activities of extracellular protease and acid phosphatase released from rhizobia decreased significantly as the concentrations of artemisinin increased. Artemisinin refluxed from Artemisia annua could thus inhibit the formation of root nodules and interfered with energy supply and reception between bacteroid and host cells. y = e(-ax) + b reflected the relationships between nitrogenase activities (y) and concentrations of artemisinin (x). In the culture medium with 48 mg x L(-1) of artemisinin, nitrogenase activities were about zero, resulting in the inactivation of nitrogenase in nodules formed. In general, artemisin in A. annua grown soils may inhibit the reproduction and growth of rhizobia, nodule formation and nitrogen biofixation, leading to less nitrogen supply, poor growth and development, and low yields of beans.

[Effects of application of N, P and K and plant density on growth of Artemisia annua and yield of artemisinin].

OBJECTIVE: To study the effects of different doses of fertilizer N,P and K and different plant densities on the growth of Artemisia annua and the yield of artemisinin which provides a scientific basis for the A. annua cultivation and artemisinin production. METHOD: Field experiment with an orthogonal experimental design L16(45) was applied. RESULT: N, P and K in moderate supplies increased significantly total biomass, leaf yield, artemisinin content in leaf and artemisinin yield under both per plant and per plot, with N and K having more effective on the artemisinin content in leaves than P. Ample N benefited the formation of leaf yield, but excess N had a significant negative effect on artemisinin content. Extra supply of P or K had hardly obvious father positive efficiency, nor negative on artemisinin content. The plant density had strong negative effects on total biomass, leaf output and artemisinin yield of single plant (per plant), but obvious positive effects on the same indices of population (per plot) with the moderate densities due to the enlarging numbers of the population; over crowded density significantly decreased artemisinin content and artemisinin yield per plot. By multiple comparison, the treatment 12 (N3P4K2 density 3) which produced the highest yields of artemisinin and artemisinin-rich leaf per plot was selected as the best in the experiment. CONCLUSION: Fertilization quantities of N, P and K fertilizer and moderate density were essential for A. annua growth and artemisinin production. The optimal application of N, P and K were respectively 300 (N), 150-300(P2O5), 210(K2O) kg x hm(-2) and the optimum density was 25 000 plant x hm(-2) nearby the test area in Chongqing.