Effect of Soybean Monoculture on the Bacterial Communities Associated with Cysts of Heterodera glycines

The soybean cyst nematode (SCN), Heterodera glycines, can cause significant reductions in soybean yield and quality in many parts of the world. Natural biological control may play an important role in regulating SCN population. In this study the bacterial communities associated with SCN cysts obtained from fields under different lengths of soybean monoculture were explored. Soil samples were collected in 2010 and 2011 from six fields that had been used for soybean monoculture for 2 to 41 yr. SCN population densities were determined and bacterial communities from SCN cysts were investigated by Biolog and PCR-DGGE methods. SCN population densities initially increased in the first 5 yr of soybean monoculture but then declined steeply as years of soybean monoculture increased. Catabolic diversity of bacterial communities associated with cysts tended to decline as number of years of monoculture increased. Some specific PCR-DGGE bands, mainly representing Streptomyces and Rhizobium, were obtained from the cysts collected from the long-term monoculture fields. Principal component analysis of Biolog and PCR-DGGE data revealed that bacterial communities associated with cysts could be divided into two groups: those from cysts obtained from shorter (< 8 yr) vs. longer (> 8 yr) monoculture. This research demonstrates that the composition of the bacterial communities obtained from SCN cysts changes with length of soybean monoculture; the suppressive impact of these bacterial communities to SCN is yet to be determined.     

Acquisition of Contextual Discrimination Involves the Appearance of a RAS-GRF1/p38 Mitogen-activated Protein (MAP) Kinase-mediated Signaling Pathway That Promotes Long Term Potentiation (LTP)

RAS-GRF1 is a guanine nucleotide exchange factor with the ability to activate RAS and RAC GTPases in response to elevated calcium levels. We previously showed that beginning at 1 month of age, RAS-GRF1 mediates NMDA-type glutamate receptor (NMDAR)-induction of long term depression in the CA1 region of the hippocampus of mice. Here we show that beginning at 2 months of age, when mice first acquire the ability to discriminate between closely related contexts, RAS-GRF1 begins to contribute to the induction of long term potentiation (LTP) in the CA1 hippocampus by mediating the action of calcium-permeable, AMPA-type glutamate receptors (CP-AMPARs). Surprisingly, LTP induction by CP-AMPARs through RAS-GRF1 occurs via activation of p38 MAP kinase rather than ERK MAP kinase, which has more frequently been linked to LTP. Moreover, contextual discrimination is blocked by knockdown of Ras-Grf1 expression specifically in the CA1 hippocampus, infusion of a p38 MAP kinase inhibitor into the CA1 hippocampus, or the injection of an inhibitor of CP-AMPARs. These findings implicate the CA1 hippocampus in the developmentally dependent capacity to distinguish closely related contexts through the appearance of a novel LTP-supporting signaling pathway.     

The Interaction of the Cellular Export Adaptor Protein Aly/REF with ICP27 Contributes to the Efficiency of Herpes Simplex Virus 1 mRNA Export

Herpes simplex virus 1 (HSV-1) protein ICP27 enables viral mRNA export by accessing the cellular mRNA export receptor TAP/NXF, which guides mRNA through the nuclear pore complex. ICP27 binds viral mRNAs and interacts with TAP/NXF, providing a link to the cellular mRNA export pathway. ICP27 also interacts with the mRNA export adaptor protein Aly/REF, which binds cellular mRNAs and also interacts with TAP/NXF. Studies using small interfering RNA (siRNA) knockdown indicated that Aly/REF is not required for cellular mRNA export, and similar knockdown studies during HSV-1 infection led us to conclude that Aly/REF may be dispensable for viral RNA export. Recently, the structural basis of the interaction of ICP27 with Aly/REF was elucidated at atomic resolution, and it was shown that three ICP27 residues, W105, R107, and L108, interface with the RNA recognition motif (RRM) domain of Aly/REF. Here, to determine the role the interaction of ICP27 and Aly/REF plays during infection, these residues were mutated to alanine, and a recombinant virus, WRL-A, was constructed. Virus production was reduced about 10-fold during WRL-A infection, and export of ICP27 protein and most viral mRNAs was less efficient. We conclude that interaction of ICP27 with Aly/REF contributes to efficient viral mRNA export.     

Anaerobic Benzene Oxidation via Phenol in Geobacter metallireducens

Anaerobic activation of benzene is expected to represent a novel biochemistry of environmental significance. Therefore, benzene metabolism was investigated in Geobacter metallireducens, the only genetically tractable organism known to anaerobically degrade benzene. Trace amounts (<0.5 μM) of phenol accumulated in cultures of Geobacter metallireducens anaerobically oxidizing benzene to carbon dioxide with the reduction of Fe(III). Phenol was not detected in cell-free controls or in Fe(II)- and benzene-containing cultures of Geobacter sulfurreducens, a Geobacter species that cannot metabolize benzene. The phenol produced in G. metallireducens cultures was labeled with ¹⁸O during growth in H₂¹⁸O, as expected for anaerobic conversion of benzene to phenol. Analysis of whole-genome gene expression patterns indicated that genes for phenol metabolism were upregulated during growth on benzene but that genes for benzoate or toluene metabolism were not, further suggesting that phenol was an intermediate in benzene metabolism. Deletion of the genes for PpsA or PpcB, subunits of two enzymes specifically required for the metabolism of phenol, removed the capacity for benzene metabolism. These results demonstrate that benzene hydroxylation to phenol is an alternative to carboxylation for anaerobic benzene activation and suggest that this may be an important metabolic route for benzene removal in petroleum-contaminated groundwaters, in which Geobacter species are considered to play an important role in anaerobic benzene degradation.     

Improving the thermostability of methyl parathion hydrolase from Ochrobactrum sp. M231 using a computationally aided method

Good protein thermostability is very important for the protein application. In this report, we propose a strategy which contained a prediction method to select residues related to protein thermal stability, but not related to protein function, and an experiment method to screen the mutants with enhanced thermostability. The prediction strategy was based on the calculated site evolutionary entropy and unfolding free energy difference between the mutant and wild-type (WT) methyl parathion hydrolase enzyme from Ochrobactrum sp. M231 [Ochr-methyl parathion hydrolase (MPH)]. As a result, seven amino acid sites within Ochr-MPH were selected and used to construct seven saturation mutagenesis libraries. The results of screening these libraries indicated that six sites could result in mutated enzymes exhibiting better thermal stability than the WT enzyme. A stepwise evolutionary approach was designed to combine these selected mutants and a mutant with four point mutations (S274Q/T183E/K197L/S192M) was selected. The T _m and T ₅₀ of the mutant enzyme were 11.7 and 10.2 °C higher, respectively, than that of the WT enzyme. The success of this design methodology for Ochr-MPH suggests that it was an efficient strategy for enhancing protein thermostability and suitable for protein engineering.     

(Z)-4-Bromo-5-(bromomethylene)-3-methylfuran-2(5H)-one sensitizes Escherichia coli persister cells to antibiotics

Persisters are a small subpopulation of bacterial cells that are dormant and extremely tolerant to antibiotics. The intrinsic antibiotic tolerance of persisters also facilitates the development of multidrug resistance through acquired mechanisms based on drug resistance genes. In this study, we demonstrate that (Z)-4-bromo-5-(bromomethylene)-3-methylfuran-2(5H)-one (BF8) can reduce persistence during Escherichia coli growth and revert the antibiotic tolerance of its persister cells. The effects of BF8 were more profound when the pH was increased from 6 to 8.5. Although BF8 is a quorum sensing (QS) inhibitor, similar effects were observed for the wild-type E. coli RP437 and its ΔluxS mutant, suggesting that these effects did not occur solely through inhibition of AI-2-mediated QS. In addition to its effects on planktonic persisters, BF8 was also found to disperse RP437 biofilms and to render associated cells more sensitive to ofloxacin. At the doses that are effective against E. coli persister cells, BF8 appeared to be safe to the tested normal mammalian cells in vitro and exhibited no long-term cytotoxicity to normal mouse tissues in vivo. These findings broadened the activities of brominated furanones and shed new light on persister control.     

Composition and dynamics of microbial community in a zeolite biofilter-membrane bioreactor treating coking wastewater

In this study, a lab-scale anaerobic/anoxic/zeolite biofilter-membrane bioreactor (A₁/A₂/ZB-MBR) was designed to treat coking wastewater. The 454 pyrosequencing was used to obtain the composition and dynamics of microbial community about the treatment system. The results showed that the system yielded stable effluent chemical oxidation demand (158.5?±?21.8 mg/L) and ammonia (8.56?±?7.30 mg/L), but fluctuant total nitrogen (31.4–165.1 mg/L) concentrations. In addition, 66,256 16S rRNA gene sequences were obtained from A₂ and ZB-MBR, and the microbial diversity and richness for five samples were determined. Although community compositions in the five samples were quite different, bacteria assigned to phylum Proteobacteria and class Flavobacteria commonly existed and dominated the microbial populations. The pyrosequencing analysis revealed that the microbial community shifted in the ZB-MBR with the presence of zeolite. Some taxa began to appear in ZB-MBR and contributed to the system performance. Additionally, Nitrosomonas and Nitrobacter gradually became the dominant ammonia-oxidizing bacteria and nitrite-oxidizing bacteria during the operation, respectively, which are favorable for the stabilized ammonia removal. Our results proved that the ZB-MBR is an alternative technique for treating coking wastewater.     

黑龙江省野生东北虎调查管理信息系统的构建

文章以黑龙江省野生东北虎（Panthera tigris altaica）野外调查数据为基础,利用地理信息系统技术、计算机技术与野生动物资源调查管理技术,构建了黑龙江省野生东北虎调查管理信息系统。主要运用面向对象程序设计语言C#和ArcGIS Engine嵌入式组件技术以及SQL Server数据库技术,设计并构建东北虎调查管理系统,实现了对野生东北虎调查数据的图形可视化操作管理。同时,结合研究区域内的自然因素和人文因素对调查资源进行动态的空间分析,及时准确地反映出东北虎的种群数量和空间变化规律,并制作出相应的分类专题图及野外分布信息统计图表等。该管理信息系统将有助于野生东北虎种群及栖息地调查数据与资料的科学管理,对于推动我国野生东北虎就地保护和科学管理具有重要意义。