Endophytic bacterial communities of field-grown potato plants and their plant-growth-promoting and antagonistic abilities

To study the effect of plant growth on potato-associated bacteria, the composition and properties of bacteria colonizing the endosphere of field-grown potato were analyzed by a multiphasic approach. The occurrence and diversity of potato-associated bacteria were monitored by a cultivation-independent approach, using terminal restriction fragment length polymorphism analysis of 16S rDNA. The patterns obtained revealed a high heterogeneity of community composition and suggested the existence of plant-specific communities. However, endophytic populations correlated to a certain extent with plant growth performance. Endophytes were also isolated from plants that grew well or grew poorly and were identified by partial sequencing of the 16S rRNA genes. A broad phylogenetic spectrum was found among isolates and differently growing plants hosted different bacterial populations. In an approach to investigate the plant-growth-promoting potential of potato-associated bacteria, a total of 35 bacteria were screened by dual testing for in vitro antagonism towards (i) the fungal pathogens Verticillium dahliae, Rhizoctonia solani, Sclerotinia sclerotiorum, and Phytophthora cactorum and (ii) the bacterial pathogens Erwinia carotovora, Streptomyces scabies, and Xanthomonas campestris. The proportion of isolates with antagonistic activity was highest against Streptomyces sp. (43%) followed by those against Xanthomonas sp. (29%). As all plants showed more or less severe disease symptoms of scab disease caused by Streptomyces scabies, we assume that the presence of the pathogen induced the colonization of antagonists. The antifungal activity of the isolates was generally low. The biotechnological potential of endophytic isolates assessed by their antagonistic activity and by in vitro production of enzymes, antibiotics, siderophores, and the plant growth hormone indole-1,3-acetic acid was generally high. Overall, seven endophytes were found to antagonize fungal as well as bacterial pathogens and showed a high production of active compounds and were therefore considered promising biological control agents.     

Characterization of a new class of potent inhibitors of the voltage-gated sodium channel Nav1.7

Voltage-gated sodium channels (Nav1) transmit pain signals from peripheral nociceptive neurons, and blockers of these channels have been shown to ameliorate a number of pain conditions. Because these drugs can have adverse effects that limit their efficacy, more potent and selective Nav1 inhibitors are being pursued. Recent human genetic data have provided strong evidence for the involvement of the peripheral nerve sodium channel subtype, Nav1.7, in the signaling of nociceptive information, highlighting the importance of identifying selective Nav1.7 blockers for the treatment of chronic pain. Using a high-throughput functional assay, novel Nav1.7 blockers, namely, the 1-benzazepin-2-one series, have recently been identified. Further characterization of these agents indicates that, in addition to high-affinity inhibition of Nav1.7 channels, selectivity against the Nav1.5 and Nav1.8 subtypes can also be achieved within this structural class. The most potent, nonselective member of this class of Nav1.7 blockers has been radiolabeled with tritium. [3H]BNZA binds with high affinity to rat brain synaptosomal membranes (Kd = 1.5 nM) and to membranes prepared from HEK293 cells stably transfected with hNav1.5 (Kd = 0.97 nM). In addition, and for the first time, high-affinity binding of a radioligand to hNav1.7 channels (Kd = 1.6 nM) was achieved with [3H]BNZA, providing an additional means for identifying selective Nav1.7 channel inhibitors. Taken together, these data suggest that members of the novel 1-benzazepin-2-one structural class of Nav1 blockers can display selectivity toward the peripheral nerve Nav1.7 channel subtype, and with appropriate pharmacokinetic and drug metabolism properties, these compounds could be developed as analgesic agents.     

Regionalizing Indicator Values for Soil Reaction in the Bavarian Alps – from Averages to Multivariate Spectra

We present an approach to produce maps of Ellenberg values for soil reaction (R-value) in the Bavarian Alps. Eleven meaningful environmental predictors covering GIS-derived information on climatic, topographic and soil conditions were used to predict R-values. As dependent variables, Ellenberg indicator values for soil reaction were queried from plot records in the vegetation database WINALPecobase. We used an additive georegression model, which combines complex prediction models and the increased prediction accuracy of a boosting algorithm. In addition to environmental predictors we included spatial effects into the model to account for spatial autocorrelation. As we were particularly interested in the usefulness of averaged R-values for spatial prediction, we applied two different models: (1) a geo-additive regression model that estimates mean R-values and (2) a proportional odds model predicting the probability distribution over R-values 1 to 9. We found meaningful dependencies between the R-value and our predictors. Both models produced the same spatial pattern of predictions. Spatial effects had an impact only in the first model. The main drawback of mean R-values is the oversimplification of complex conditions of soil reaction, which is entailed by averaging and regression to mean values. Therefore, regionalized average indicator values provide only limited information on site-ecological characteristics. Model 1 failed to predict the range and shapes of original indicator spectra precisely. In contrast, the second model provided a more sophisticated picture of soil reaction. To make the multivariate output of model 2 comparable to that of model 1, we propose to plot the distribution in a three-dimensional color-space. In addition, comparison of both models based on a multiple linear regression model resulted in a R ² of 0.93. The proportional odds model is a promising approach also for other indicator values and different regions as well as for other ordinal-scaled ecological parameters.     

Coppicing shifts CO2 stimulation of poplar productivity to above-ground pools: a synthesis of leaf to stand level results from the POP/EUROFACE experiment

A poplar short rotation coppice (SRC) grown for the production of bioenergy can combine carbon (C) storage with fossil fuel substitution. Here, we summarize the responses of a poplar ( Populus ) plantation to 6 yr of free air CO₂ enrichment (POP/EUROFACE consisting of two rotation cycles). We show that a poplar plantation growing in nonlimiting light, nutrient and water conditions will significantly increase its productivity in elevated CO₂ concentrations ([CO₂]). Increased biomass yield resulted from an early growth enhancement and photosynthesis did not acclimate to elevated [CO₂]. Sufficient nutrient availability, increased nitrogen use efficiency (NUE) and the large sink capacity of poplars contributed to the sustained increase in C uptake over 6 yr. Additional C taken up in high [CO₂] was mainly invested into woody biomass pools. Coppicing increased yield by 66% and partly shifted the extra C uptake in elevated [CO₂] to above-ground pools, as fine root biomass declined and its [CO₂] stimulation disappeared. Mineral soil C increased equally in ambient and elevated [CO₂] during the 6 yr experiment. However, elevated [CO₂] increased the stabilization of C in the mineral soil. Increased productivity of a poplar SRC in elevated [CO₂] may allow shorter rotation cycles, enhancing the viability of SRC for biofuel production.     

干旱区胡杨叶片含水量和叶绿素含量特征

在阿拉干样区内,距河道不同距离选取40棵胡杨树(Populus euphratica)采样,使用相关分析方法探讨胡杨叶片相对含水量(fuel moisture content,FMC)、等效水厚度(equiv-alent water thickness,EWT)、叶绿素含量随距河道距离的空间差异,以及随地面温度的变化特征,并讨论了FMC、EWT和叶绿素含量之间的相关性。结果表明:FMC、EWT、叶绿素含量与河道距离有极显著的相关关系(P<0.01)。距河道越远,3项指标均随距河道距离的增加极显著的减少,其中EWT与距河道距离的相关性最大(-0.577)。温度变化对FMC和EWT均有极显著的影响(P<0.01),但对叶绿素含量影响不大(P>0.05)。因FMC、EWT的物理含义不同,它们的平均值在胡杨树个体尺度/水平上极显著相关,但在单片叶子尺度上FMC和EWT之间无显著相关(P>0.05),而胡杨树个体平均和单片叶子的EWT与叶绿素含量均极显著相关(P<0.01)。由于EWT与距河道距离和叶绿素含量的相关性极显著,而且对温度变化不敏感,因此,具有很好的开发应用潜力,建议将EWT作为干旱区河岸生态系统植被含水量遥感监测的一个指标。     

In the footsteps of sea stars: deciphering the catalogue of proteins involved in underwater temporary adhesion

Sea stars adhere strongly but temporarily to underwater substrata via the secretion of a blend of proteins, forming an adhesive footprint that they leave on the surface after detachment. Their tube feet enclose a duo-gland adhesive system comprising two types of adhesive cells, contributing different layers of the footprint and de-adhesive cells. In this study, we characterized the catalogue of sea star footprint proteins (Sfps) in the species Asterias rubens to gain insights in their potential function. We identified 16 Sfps and mapped their expression to type 1 and/or type 2 adhesive cells or to de-adhesive cells by double fluorescent in situ hybridization. Based on their cellular expression pattern and their conserved functional domains, we propose that the identified Sfps serve different functions during attachment, with two Sfps coupling to the surface, six providing cohesive strength and the rest forming a binding matrix. Immunolabelling of footprints with antibodies directed against one protein of each category confirmed these roles. A de-adhesive gland cell-specific astacin-like proteinase presumably weakens the bond between the adhesive material and the tube foot surface during detachment. Overall, we provide a model for temporary adhesion in sea stars, including a comprehensive list of the proteins involved.     

Acrylyl-Coenzyme A Reductase,an Enzyme Involved in the Assimilation of 3-Hydroxypropionate by Rhodobacter sphaeroides

The anoxygenic phototroph Rhodobacter sphaeroides uses 3-hydroxypropionate as a sole carbon source for growth. Previously, we showed that the gene (RSP_1434) known as acuI, which encodes a protein of the medium-chain dehydrogenase/reductase (MDR) superfamily, was involved in 3-hydroxypropionate assimilation via the reductive conversion to propionyl-coenzyme A (CoA). Based on these results, we speculated that acuI encoded acrylyl-CoA reductase. In this work, we characterize the in vitro enzyme activity of purified, recombinant AcuI using a coupled spectrophotometric assay. AcuI from R. sphaeroides catalyzes the NADPH-dependent acrylyl-CoA reduction to produce propionyl-CoA. Two other members of the MDR012 family within the MDR superfamily, the products of SPO_1914 from Ruegeria pomeroyi and yhdH from Escherichia coli, were shown to also be part of this new class of NADPH-dependent acrylyl-CoA reductases. The activities of the three enzymes were characterized by an extremely low K_m for acrylyl-CoA (<3 μM) and turnover numbers of 45 to 80 s⁻¹. These homodimeric enzymes were highly specific for NADPH (K_m = 18 to 33 μM), with catalytic efficiencies of more than 10-fold higher for NADPH than for NADH. The introduction of codon-optimized SPO_1914 or yhdH into a ΔacuI::kan mutant of R. sphaeroides on a plasmid complemented 3-hydroxypropionate-dependent growth. However, in their native hosts, SPO_1914 and yhdH are believed to function in the metabolism of substrates other than 3-hydroxypropionate, where acrylyl-CoA is an intermediate. Complementation of the ΔacuI::kan mutant phenotype by crotonyl-CoA carboxylase/reductase from R. sphaeroides was attributed to the fact that the enzyme also uses acrylyl-CoA as a substrate.     

Serratia odorifera: analysis of volatile emission and biological impact of volatile compounds on Arabidopsis thaliana

Bacteria emit a wealth of volatiles. The combination of coupled gas chromatography/mass spectrometry (GC/MS) and proton-transfer-reaction mass spectrometry (PTR-MS) analyses provided a most comprehensive profile of volatiles of the rhizobacterium Serratia odorifera 4Rx13. An array of compounds, highly dominated by sodorifen (approximately 50%), a bicyclic oligomethyl octadiene, could be detected. Other volatiles included components of the biogeochemical sulfur cycle such as dimethyl disulfide (DMDS), dimethyl trisulfide and methanethiol, terpenoids, 2-phenylethanol, and other aromatic compounds. The composition of the bouquet of S. odorifera did not change significantly during the different growth intervals. At the beginning of the stationary phase, 60 μg of volatiles per 24 h and 60 easily detectable components were released. Ammonia was also released by S. odorifera, while ethylene, nitric oxide (NO) and hydrogen cyanide (HCN) could not be detected. Dual culture assays proved that 20 μmol DMDS and 2.5 μmol ammonia, individually applied, represent the IC₅₀ concentrations that cause negative effects on Arabidopsis thaliana.     

Raman microspectroscopic discrimination of TCam-2 cultures reveals the presence of two sub-populations of cells

TCam-2 cells are the main in vitro model for investigations into seminomatous tumors. However, despite their widespread use, questions remain regarding the cells’ homogeneity and consequently how representative they are of seminomas. We assess the TCam-2 cell line using routine and novel authentication methods to determine its homogeneity, identify any cellular sub-populations and resolve whether any changes could be due to generational differentiation. TCam-2, embryonal carcinoma cells (2102EP) and breast cancer cell (MCF7) lines were assessed using qRT-PCR, immunocytochemistry, flow cytometry and short tandem repeat analyses. Raman maps of individual cells (minimum of 10) and single scan spectra from 200 cells per culture were obtained. TCam-2s displayed the characteristic marker gene expression pattern for seminoma, were uniform in size and granularity and short tandem repeat analysis showed no contamination. However, based only on physical parameters, flowcytometry was unable to differentiate between TCam-2 and 2102EPs. Raman maps of TCam-2s comprised three equally distributed, distinct spectral patterns displaying large intercellular single spectral variation. All other cells showed little variation. Principal component, cluster and local spectral angle analyses indicated that the TCam-2s contained two different types of cells, one of which comprised two subgroups and was similar to some 2102EP cells. Protein expression corroborated the presence of different cells and generational differences. The detailed characterization provided by the Raman spectra, augmented by the routine methods, provide substantiation to the long-held suspicion that TCam-2 are not homogeneous but comprise differing cell populations, one of which may be embryonal carcinoma in origin.