Establishing a genetic system for ecological studies of Streptococcus oligofermentans

Streptococcus oligofermentans is a newly characterized species belonging to the mitis group of oral streptococci. So far no correlation has been demonstrated between S. oligofermentans and dental caries. Furthermore, a reverse correlation has been observed between the number of S. oligofermentans and the number of Streptococcus mutans, a major cariogenic pathogen, in the oral cavity. These properties suggest that S. oligofermentans may have a potential to be used as a 'probiotics' for caries prevention. In this study, we aim to establish a genetic system in S. oligofermentans to further study the biology of this new species. Using homologous regions of the comCDE locus in other streptococci, the comC gene was isolated and sequenced. A synthetic competence-stimulating peptide (CSP) was synthesized and shown to be able to effectively induce competence in S. oligofermentans. This CSP-induced transformation system in S. oligofermentans was used to construct green fluorescent protein (gfp) and luciferase (luc) reporter systems, both of which are driven by the lactate dehydrogenase (ldh) promoter. These reporter systems were further shown to be highly expressed in planktonic and biofilm cells, suggesting that these reporter systems can be used in future ecological studies of S. oligofermentans.     

Application of ecological engineering principles in agriculture

To what extent modern industrialized agriculture violates the principles of ecological engineering and which changes agriculture needs to make to be consistent with these principles are discussed. The 12 ecological principles presented are used as the starting point for this discussion. For each principle it is discussed how the agriculture of today violates these principles and how relatively small changes could make the agriculture more according to ecological engineering concepts.     

A meta-analysis of tradeoffs between plant tolerance and resistance to herbivores: combining the evidence from ecological and agricultural studies

Resistance and tolerance represent two general strategies of plant defence against herbivores. Since resources available for allocation to defence are limited and resistance and tolerance are likely to serve the same functions for plants, the occurrence of trade offs between these two strategies has been assumed. We review the empirical evidence for tolerance–resistance tradeoffs by means of meta‐analysis of genetic correlations between resistance and tolerance obtained from 31 ecological and agricultural studies published during 1980–2003 and conducted on 17 different plant species. The sign of the relationship between tolerance and resistance differed depending on the type of plants examined. Tolerance and resistance tended to be positively correlated in crops and negatively correlated in wild plants, but the mean correlation coefficients in both plant types were not significantly different from zero. The magnitude of correlations was affected neither by the tolerance measure (reduction in growth or in fitness in damaged plants) nor by the resistance measure used (inverse of damage, antibiosis, antixenosis, or specific resistance trait). In wild plants correlations between resistance and tolerance were significantly negative (r=?0.069) only in studies where resistance was assessed as a specific chemical or mechanical resistance trait, but this correlation is based only on two studies. No difference in the mean resistance–tolerance correlations was found between studies conducted in the field and in the greenhouse; in both cases mean correlations tended to be positive. The results of our analysis indicate that conditions under which a negative association between resistance and tolerance occurs and, thus, the evolution of multiple defensive strategies in plants is constrained, are much more restrictive than previously assumed. However, the currently available studies are still scarce and taxonomically skewed to allow a thorough analysis of sources of variation in resistance–tolerance relationship. Specifically, we need more studies examining the relationship between specific resistance and tolerance traits, studies on perennial plants and under different environmental conditions.     

An ecological perspective on U.S. industrial poultry production: the role of anthropogenic ecosystems on the emergence of drug-resistant bacteria from agricultural environments

The industrialization of food animal production, specifically the widespread use of antimicrobials, not only increased pressure on microbial populations, but also changed the ecosystems in which antimicrobials and bacteria interact. In this review, we argue that industrial food animal production (IFAP) is appropriately defined as an anthropogenic ecosystem. This paper uses an ecosystem perspective to frame an examination of these changes in the context of U.S. broiler chicken production. This perspective emphasizes multiple modes by which IFAP has altered microbiomes and also suggests a means of generating hypotheses for understanding and predicting the ecological impacts of IFAP in terms of the resistome and the flow of resistance within and between microbiomes.     

Isolation and identification of Acanthamoeba species from thermal spring environments in southern Taiwan

Acanthamoeba species are free-living amoebae found in a range of environments. Within this genus, a number of species are recognized as human pathogens, potentially causing Acanthamoeba keratitis, granulomatous amoebic encephalitis, and chronic granulomatous lesions. In this study, 60 water samples were taken from four thermal spring recreation areas in southern Taiwan. We detected living Acanthamoeba spp. based on culture-confirmed detection combined with the molecular taxonomic identification method. Living Acanthamoeba spp. were detected in nine (15%) samples. The presence or absence of Acanthamoeba spp. in the water samples depended significantly on the pH value. The most frequently identified living Acanthamoeba genotype was T15 followed by T4, Acanthamoeba spp., and T2. Genotypes T2, T4, and T15 of Acanthamoeba, are responsible for Acanthamoeba keratitis as well as granulomatous amoebic encephalitis, and should therefore be considered a potential health risk associated with human activities in thermal spring environments.     

不同生态环境野生大豆的结构比较研究

对生长在不同生态环境的蝶形花科Ｆａｂａｃｅａｅ 大豆属Ｇｌｙｃｉｎｅ 的两个野生大豆Ｇ．ｓｏｊａ 品系进行了扫描电镜观察及比较研究．结果表明,生长在盐渍生态环境的野生大豆茎和叶体表都具有盐腺,盐腺圆球型,基部有一个小柄,着生在盐生野生大豆茎、叶表皮外切向壁的胞间层处．幼嫩的盐腺靠泌盐孔泌盐,成熟的盐腺靠整体破碎释盐．而生长在黑土地生态环境的野生大豆的茎和叶外切向壁未发现有泌盐的盐腺,其茎叶的表皮都呈现出平滑状态．因此两种不同生态环境的同科同属植物在微观结构上显示出明显差异．     

Biodiversity and persistence of ecological communities in variable environments

Recent analyses of climate data indicate that the intensity and frequency of different weather extremes have increased. Such increased environmental variability may lead to increased species extinction rates and hence have important consequences for the long-term persistence of ecological communities. Here we use model communities in order to investigate the relationship between species richness and community persistence in a fluctuating environment. We model two scenarios: (1) correlated species responses to environmental fluctuations and (2) uncorrelated (independent) species responses. We quantify the risk and extent of species extinctions using the so-called community viability analysis. It is shown that species-rich communities are more sensitive to environmental stochasticity than species-poor communities. Specifically, per species risk of extinction is higher in species-rich communities than in species-poor ones. Moreover, for a given species richness, communities with uncorrelated species responses to environmental variation run a considerable higher risk of losing a fixed proportion of species compared with communities with correlated species responses. We discuss the compatibility of these results with the ecological insurance hypothesis.     

农业景观的生态规划与设计

从景观生态学的基本理论出发,探讨农业景观的生态规划与设计原理及方法,认为因涉及问题的宏观空间性、关联性及综合性等特点,使农业景观的生态规划与设计成为景观生态学的重要应用领域,进而以地处我国半干旱半湿润地带冀西北涿盆地进行了案实践。     

First principles studies of the graphene-phenol interactions

Studies of the interaction between phenol and intrinsic graphene, as well as phenol and aluminum doped graphene layer are performed using first principles total energy calculations within the periodic density functional theory. A 4x4 periodic structure is used to explore the adsorption of a phenol molecule on the intrinsic graphene and on aluminum doped graphene layer. The electron-ion interactions are modeled using ultra-soft pseudo-potentials, and the exchange-correlation energies are treated according to the generalized gradient approximation (GGA) with the PBE parameterization. We consider different molecule orientations: parallel and perpendicular to the graphene layer to relax the atomic structure. To explain the optimized atomic geometry we determine binding energies for all cases and the density of states (DOS) and partial DOS for the most relevant configurations. Results indicate that the direct interaction of oxygen with aluminum yields the ground state geometry with the phenol molecule adsorbed on the graphene layer. Binding energies and DOS structures also demonstrate that the ground state configuration is that where the O and Al atoms interact with a separation distance of 1.97 ?.     

Tryptophan environments in glutathione transferase of human placenta from temperature-dependent phosphorescence studies

An investigation of the tryptophan emission properties of glutathione transferase from human placenta was conducted in order to characterize the environments of the two aromatic residues. The low-temperature phosphorescence spectra and temperature dependence of the phosphorescence quantum yield of the tryptophan residues revealed a difference in the chemical nature and dynamical structure of the surrounding protein matrix. Thus, one tryptophan residue seems to be deeply embedded within the polypeptide in a rigid weakly polar environment, characteristic of a beta-type secondary structure. The other is located in a more polar site, probably near the surface, in a rather flexible region of the macromolecule. At high temperature, the heterogeneity in the triplet lifetime of the internal residue attests to the presence of multiple conformers which are not in rapid equilibrium in the phosphorescence time scale. The anisotropy of the phosphorescence emission of glutathione transferase indicates that no energy transfer occurs between the two residues, and measurement of the rotational correlation time yields an hydrodynamic volume which is in good agreement with the molecular weight reported in the literature for the dimer.     

绿色食品基地的景观生态规划

在介绍景观生态规划、绿色食品基本概念的基础上,提出了景观生态规划在绿色食品基地建设中的意义,重点阐述了绿色食品基地的景观生态规划应遵循可持续发展和资源永续利用、系统综合性、因地制宜、景观异质性等原则。结合抚顺市绿色食品基地景观生态规划,分析了确定规划范围与规划目标、景观生态调查、景观空间格局与生态过程分析、景观生态适宜性分析、景观功能区划分等规划步骤,并探讨了此项规划的成功之处。     

农田有害生物综合治理在生态农业中的地位

农业是以生物生产为基础的产业 ,对资源具有高度依靠性。面对短缺的自然资源和脆弱的农业生态环境 ,我国植保科技界提出“预防为主 ,综合防治”植保方针 ,推广农作物病虫综防技术防治主要病虫害。农业部在实施可持续发展战略中 ,针对农业对资源的浪费 ,及农产品对消费者安全放在首位的观念 ,提出生态农业建设任务。生态农业建设将有力推动农作物有害生物的综合治理 ,本文就福建省连城县综防技术浅析两者间的同一性。1　农作物病虫综合防治技术与有害生物综合治理目标1 .1　综合防治的主体技术综防的主体技术主要有农业生态防治、生物技术防…     

Stability of floral specialization in Trollius europaeus in contrasting ecological environments

Specialization of some plants on seed‐eating pollinators is intriguing, especially when co‐pollinators exclusively feeding on nectar are also present. We examined the stability of the morphological specialization of Trollius europaeus (L.) globeflowers with respect to Chiastocheta (Pokorny) flies by artificially opening the flowers. In the montane and subalpine environments studied, other visitors contributed 2% and 28% of all the visits, respectively, and visited open flowers nearly eight times more often than closed flowers, but in both environments their contribution to pollination did not compensate for Chiastocheta aversion against open phenotypes. Net seed set (female success) was slightly higher (+4%) and pollen export (male success) was much higher (+85%) for closed than open flowers. Selection in favour of the closed phenotype was even more intense in patches where open phenotypes were most common, precluding the evolution of open flowers in the study populations.     

Environmental impact assessment of agricultural production in Chongming ecological island

The International Journal of Life Cycle Assessment - Evaluate environmental load of the agriculture industry by taking Chongming Island of Shanghai as a case study. Propose feasible approaches to...