How (not) to model autonomous behaviour

Autonomous systems are the result of self-sustaining processes of constitution of an identity under precarious circumstances. They may transit through different modes of dynamical engagement with their environment, from committed ongoing coping to open susceptibility to external demands. This paper discusses these two statements and presents examples of models of autonomous behaviour using methods in evolutionary robotics. A model of an agent capable of issuing self-instructions demonstrates the fragility of modelling autonomy as a function rather than as a property of a system's organization. An alternative model of behavioural preference based on homeostatic adaptation avoids this problem by establishing a mutual constraining between lower-level processes (neural dynamics and sensorimotor interaction) and higher-level metadynamics (experience-dependent, homeostatic triggering of local plasticity and re-organization). The results of these models are lessons about how strong autonomy should be approached: neither as a function, nor as a matter of external vs. internal determination.     

The role of natural plant products in modulating the immune system: An adaptable approach for combating disease in grazing animals

Plants provide herbivores with an array of chemicals with the potential to improve health and well-being. For instance, phytochemicals, known as secondary compounds, which protect plants from consumers and pests can adversely affect cellular and metabolic processes in herbivores, but at low doses and in appropriate mixtures, they can have beneficial effects on animal nutrition and health, though the latter has not been explored in great breadth or depth. In this review, we summarize the potential impact of natural plant products on immunomodulation and other therapeutic effects in herbivores. Development of preventative strategies to help animals resist disease would be a more economical, ecological and socially effective long-term healthcare strategy than treating diseases. In this realm, immunomodulation promoted by forages emerges as an interesting alternative and complement to chemotherapy. The challenge for feeding systems will be to incorporate mixes of plants with bioactive properties in ways that enhance health without compromising animal production and well-being. A solution to this challenge may involve developing management programs that acknowledge the ability of animals to learn about the beneficial effects of diverse foods.     

Tannins and self-medication: Implications for sustainable parasite control in herbivores

Animals adapt to the variability of the external environment and to their changing internal needs not only by generating homeostatic physiological responses, but also by operating in the external environment. In this study, we determined whether sheep with a gastrointestinal parasite infection increased intake of a low-quality food containing a natural antiparasitic agent (tannins) relative to non-parasitized sheep. Four groups of lambs (n = 8 lambs/group) were assigned to a 2 × 2 factorial design with parasitic burden (P = parasites; NP = no parasites) and the offer of a supplement containing tannins (yes, no) as the main factors. Parasitized lambs ate more of the tannin-containing food than non-parasitized lambs for the first 12 days of the study, when parasite burdens were high, but differences became smaller and disappeared toward the end of the study when parasite burdens decreased. This result suggests the lambs detected the presence of internal parasites or associated symptoms and modified their ingestion of an antiparasitic agent as a function of need.     

The role of neuropeptides in caterpillar nutritional ecology

Plant diet strongly impacts the fitness of insect herbivores. Immediately, we think of plant defensive compounds that may act as feeding deterrents or toxins. We are, probably, less aware that plants also influence insect growth and fecundity through their nutritional quality. However, most herbivores respond to their environment and select the diet which optimizes their growth and development. This regulation of nutritional balance may occur on many levels: through selecting and ingesting appropriate plant tissue and nutrient digestion, absorption and utilization. Here, we review evidence of how nutritional requirements, particularly leaf protein to digestible carbohydrate ratios, affect caterpillar herbivores. We propose a model where midgut endocrine cells assess and integrate hemolymph nutritional status and gut content and release peptides which influence digestive processes. Understanding the effects of diet on the insect herbivore is essential for the rational design and implementation of sustainable pest management practices.     

The cell membrane and the struggle for life of lactic acid bacteria

The major life-threatening event for lactic acid bacteria (LAB) in their natural environment is the depletion of their energy sources and LAB can survive such conditions only for a short period of time. During periods of starvation LAB can exploit optimally the potential energy sources in their environment usually by applying proton motive force generating membrane transport systems. These systems include in addition to the proton translocating F_oF₁-ATPase: a respiratory chain when hemin is present in the medium, electrogenic solute uptake and excretion systems, electrogenic lactate/proton symport and precursor/ product exchange systems. Most of these metabolic energy-generating systems offer as additional bonus the prevention of a lethal decrease of the internal and external pH. LAB have limited biosynthetic capacities and rely heavily on the presence of essential components such as sources of amino acids in their environment. The uptake of amino acids requires a major fraction of the available metabolic energy of LAB. The metabolic energy cost of amino acid uptake can be reduced drastically by accumulating oligopeptides instead of the individual amino acids and by proton motive force-generating efflux of excessively accumulated amino acids. Other life-threatening conditions that LAB encounter in their environment are rapid changes in the osmolality and the exposure to cytotoxic compounds, including antibiotics. LAB respond to osmotic upshock or downshock by accumulating or releasing rapidly osmolytes such as glycine-betaine. The life-threatening presence of cytotoxic compounds, including antibiotics, is effectively counteracted by powerful drug extruding multidrug resistance systems. The number and variety of defense mechanisms in LAB is surprisingly high. Most defense mechanisms operate in the cytoplasmic membrane to control the internal environment and the energetic status of LAB. Annotation of the functions of the genes in the genomes of LAB will undoubtely reveal additional defense mechanisms.     

Agriculture: the real nexus for enhancing bioavailable micronutrients in food crops

Human existence requires that agriculture provide at least 50 nutrients (e.g., vitamins, minerals, trace elements, amino acids, essential fatty acids) in amounts needed to meet metabolic demands during all seasons. If national food systems do not meet these demands, mortality and morbidity rates increase, worker productivity declines, livelihoods are diminished and societies suffer. Today, many food systems within the developing world cannot meet the nutritional needs of the societies they support mostly due to farming systems that cannot produce enough micronutrients to meet human needs throughout the year. Nutrition transitions are also occurring in many rapidly developing countries that are causing chronic disease (e.g., cancer, heart disease, stroke, diabetes, and osteoporosis) rates to increase substantially. These global developments point to the need to explicitly link agricultural technologies to human health. This paper reviews some ways in which agriculture can contribute significantly to reducing micronutrient malnutrition globally. It concludes that it is imperative that close linkages be forged between the agriculture, nutrition and health arenas in order to find sustainable solutions to micronutrient malnutrition with agriculture becoming the primary intervention tool to use in this fight.     

未来食品的低碳生物制造

受到人口增长过快、社会经济发展水平不平衡、人口老龄化和不健康饮食方式等影响,人类面临着食品和营养缺乏、部分人群中营养相关疾病高发等问题。同时,社会低碳发展的需求呼唤一种可持续的食物供给模式。因此,既能满足消费者口感和营养需求,又是绿色可持续食物供给模式的技术,例如功能糖、人造肉等未来食品技术,受到了广泛的关注。近年,新兴的生物制造技术及产品得到了迅猛发展,将会支撑形成绿色、低碳的未来食品产业,引发传统生产模式的深刻变革,是新兴生物经济的重大战略发展方向。本文聚焦于未来食品——功能糖、微生物蛋白及人造肉等关键辅配料的生物制造技术研究,追踪其在细胞工厂构建、工业环境下菌种测试与过程优化和衍生产品开发等研究的最新进展,展望未来的发展趋势,旨在为微生物制造未来食品的产业发展提供指导。     

Plant root growth, architecture and function

Without roots there would be no rhizosphere and no rhizodeposition to fuel microbial activity. Although micro-organisms may view roots merely as a source of carbon supply this belies the fascinating complexity and diversity of root systems that occurs despite their common function. Here, we examine the physiological and genetic determinants of root growth and the complex, yet varied and flexible, root architecture that results. The main functions of root systems are also explored including how roots cope with nutrient acquisition from the heterogeneous soil environment and their ability to form mutualistic associations with key soil micro-organisms (such as nitrogen fixing bacteria and mycorrhizal fungi) to aid them in their quest for nutrients. Finally, some key biotic and abiotic constraints on root development and function in the soil environment are examined and some of the adaptations roots have evolved to counter such stresses discussed.     

Metabolic engineering of plant secondary products

Plants interact with their environment by producing a diverse array of secondary metabolites. Many of these compounds are valued for their medicinal, industrial or agricultural properties. Other secondary products are toxic or otherwise undesirable and can reduce the commercial value of crops. Gene transfer technology offers new opportunities to modify directly plant secondary product synthesis through metabolic engineering. This article reviews some of the strategies which have been used to increase or decrease the synthesis of specific plant metabolites, as well as methods for expanding the biosynthetic capabilities of individual species.     

Dynamics of savanna ecosystems

Abstract. Theories concerning the factors involved in the dynamics of savannas, particularly the tree-grass interface, are reviewed. Emphasis is put on factors related to soil moisture, soil nutrients, fire and large herbivores. The distinction between external (independent) and internal (dependent, interactive) environment is discussed and it is explained how this distinction is affected by the scale of observation.     

Vertebrate herbivores and plants in the Arctic and subarctic: effects on individuals, populations, communities and ecosystems

Plants in the Arctic and subarctic face the problems posed by herbivory in addition to short growth seasons, low temperatures and low nutrient availability. Herbivores control plant performance by removing biomass, by altering resource availability, by altering the physical environment, and by changing the balance of competition. The main difference between effects of herbivores in the Arctic and at lower latitudes may be the relatively greater importance of changes in resource availability and the physical environment resulting from herbivore activity, and their consequences for plant competitive abilities.Species responses to defoliation depend primarily on growth form. Artificial defoliation of graminoids has negative effects on most species, but in the field total effects of herbivores are often neutral or even positive, resulting in increased nitrogen concentrations in shoots in many species. Shrubs are less able to respond positively to herbivory than graminoids, and although there is some evidence that deciduous shrubs recover faster than evergreen ones, the difference is not great. However, effects of herbivores on shrubs are little studied, despite their importance in the herbivore diet.Responses of individual species to increased nutrient availability vary greatly, even within a growth form. Some graminoids and shrubs show strong positive responses to fertilization while others show little or no response. These species-specific effects suggest that herbivores can alter interspecific relationships through differential responses to fertilization. Herbivores may alter plant population dynamics by altering flower or seed production, by consuming seedlings, or by altering the availability of microsites. However, no study has adequately examined this for any arctic species.Changes in community composition following removal of herbivores are the result not only of selective removal of some plant species, but also of changes in microsite availability, nutrient availability, litter accumulation, and soil characteristics. Thus, the view that abiotic factors are the overwhelming determinants of community structure in low-productivity environments is compatible with the view that herbivores exercise their influence to a large extent by altering abiotic factors.Arctic herbivores often increase total above-ground nitrogen availability (and therefore food quality) in the plant community, but increased productivity as a result of herbivores is rare. The increase in nutrient availability is probably due in part to changes in soil temperature and soil moisture following a reduction in litter accumulation.Although our knowledge of effects of herbivory on individual plants and on communities is extensive, we lack information on effects at the population level. We also do not have an adequate understanding of impacts of herbivores at different spatial and temporal scales, something which is needed to be able to make predictions about longer-term impact of herbivores in these systems.     

Parasitoids select plants more heavily infested with their caterpillar hosts: a new approach to aid interpretation of plant headspace volatiles

Plants produce volatile organic compounds (VOCs) in response to herbivore attack, and these VOCs can be used by parasitoids of the herbivore as host location cues. We investigated the behavioural responses of the parasitoid Cotesia vestalis to VOCs from a plant-herbivore complex consisting of cabbage plants (Brassica oleracea) and the parasitoids host caterpillar, Plutella xylostella. A Y-tube olfactometer was used to compare the parasitoids' responses to VOCs produced as a result of different levels of attack by the caterpillar and equivalent levels of mechanical damage. Headspace VOC production by these plant treatments was examined using gas chromatography-mass spectrometry. Cotesia vestalis were able to exploit quantitative and qualitative differences in volatile emissions, from the plant-herbivore complex, produced as a result of different numbers of herbivores feeding. Cotesia vestalis showed a preference for plants with more herbivores and herbivore damage, but did not distinguish between different levels of mechanical damage. Volatile profiles of plants with different levels of herbivores/herbivore damage could also be separated by canonical discriminant analyses. Analyses revealed a number of compounds whose emission increased significantly with herbivore load, and these VOCs may be particularly good indicators of herbivore number, as the parasitoid processes cues from its external environment.     

Exploitation of secondary metabolites by animals: A response to homeostatic challenges

We propose that the exploitation of the bioactive properties of secondary metabolites (SMs) by animals can provide a "treatment" against various challenges that perturb homeostasis in animals. The unified theoretical framework for the exploitation of SMs by animals is based on a synthesis of research from a wide range of fields and although it is focused on providing generalized predictions for herbivores that exploit SMs of plants, predictions can be applied to understand the exploitation of SMs by many animals. In this review, we argue that the probability of SM exploitation is determined by the relative difference between the cost of a homeostatic challenge and the toxicity of the SM and we provide various predictions that can be made when considering behavior under a homeostatic perspective. The notion that animals experience and respond to costly challenges by exploiting therapeutic SMs provides a relatively novel perspective to explain foraging behavior in herbivores, specifically, and behavior of animals in general. We provide evidence that animals can exploit the biological activity of SMs to mitigate the costs of infection by parasites, enhance reproduction, moderate thermoregulation, avoid predation, and increase alertness. We stress that a better understanding of animal behavior requires that ecologists look beyond their biases that SMs elicit punishment and consider a broader view of avoidance or selection of SMs relative to the homeostatic state. Finally, we explain how understanding exploitation of SMs by animals could be applied to advance practices of animal management and lead to discovery of new drugs.     

可持续发展指标体系的构建方法探讨

以未来、社会平等、公众参与和生态环境保护等可持续发展原理为理论基础,提出一个建立持续性指标的方法论框架,试图在多种时空尺度上满足用户的不同要求．     

利用农业生物多样性持续控制有害生物

农业生物多样性对保障全球粮食安全和农业可持续发展至关重要.人类在多样性的形成上发挥了关键作用,人类结合自然进化创造了遗传多样性、物种多样性和生态系统多样性.农业生物多样性发挥了很多社会经济和环境功能:保障粮食安全;维持农业生态系统可持续发展;赋予农村经济适变性.但当前人类毁灭农业生物多样性的速度更为惊人.在总结石油农业单一化种植的生态负效应、传统农业提倡“天人合一”的生态正效应的基础上,分析讨论了利用农业生物多样性持续控制有害生物的必要性和可行性,从生态系统多样性、物种多样性和种内遗传多样性3个层次,归纳了构建和恢复农田生物多样性的基本方法.基于病理学、生态学、营养学和生理学等学科领域,从群体异质效应、稀释效应、微生态效应、诱导抗性效应、物理阻隔效应、生理学效应和化感效应等7个方面,归纳了利用农业生物多样性持续控制有害生物的基础原理.寻求低投入、高效益、多样化和可持续的农业生产系统是当今世界许多科学家、决策者和生产者共同关心的问题.农业生物多样性具有重要的生态作用,在现代农业框架下,是合情合理构建持续、稳定、健康、高产的农田生态系统,持续控制有害生物的金钥匙.为此必须加强四方面的课题研究:各种作物之间的相生相克关系及其作用机理;各种有害生物的主要天敌种类、生物学、生态学特性及其适生环境;利用农业生物多样性全面、持续控制有害生物的农业生产模式;与其相配套的农艺措施与农业机械.     

Neurotransmitters and stress

In this article definitions of stress and distress are proposed and the relationships between stress and activities of neurohormonal systems explored. The idea is developed that stress is a condition where expectations--whether genetically programmed, established by prior learning, or deduced from circumstances--do not match the current or anticipated perceptions of the internal or external environment, and this discrepancy between what is observed or sensed and what is expected or programmed elicits patterned, compensatory responses. Distress is viewed here as a form of stress characterized by specific behavioral and autonomic communicated signs, pituitary-adrenocortical and sympathoadrenomedullary activation, and a negative experience that motivates escape or avoidance. During stress, many body systems--including the sympathoadrenal, parasympathetic, and hormonal homeostatic systems--are activated or inhibited in primitively specific patterns regulated by physiological, biochemical, and psychological homeostats. Many of these patterns, which are at least partly inherited, can be understood teleologically on the basis of preservation of the internal environmental and natural selection in evolution.     

Nigella sativa L.: Uses in traditional and contemporary medicines – An overview

There are several wild and cultivated plants that offer excellent opportunities for being used as herbal and therapeutic agents. The identification of medicinal properties of plants and their effectiveness in treating diseases are important components in medicinal plant research and this can pave ways for further improvements in traditional drug use. Climatic conditions and phytogeography in Pakistan are ideal for naturally occurring diverse flora and managed cultivation of hundreds of plants of medicinal significance. Nigella sativa commonly known as the black seed is an important medicinal plant that has been widely used as a multipurpose medicinal agent in different countries since old times. The plant is abundantly cultivated in Pakistan for uses as condiment and medicines. It possesses important classes of bioactive compounds among which thymoquinone has attracted significant attention from the scientific community because of its active role in treating a diverse spectrum of diseases. The black seeds are used for reducing adverse effects of arthritis, asthma, inflammation, liver and gastro disorders besides their potential role in diabetes and cancers. The focus of this review is to highlight the medicinal significance of N. sativa in traditional medicine and opportunities for exploitation in contemporary medicine.     

Dynamic control in metabolic engineering: Theories,tools, and applications

Metabolic engineering has allowed the production of a diverse number of valuable chemicals using microbial organisms. Many biological challenges for improving bio-production exist which limit performance and slow the commercialization of metabolically engineered systems. Dynamic metabolic engineering is a rapidly developing field that seeks to address these challenges through the design of genetically encoded metabolic control systems which allow cells to autonomously adjust their flux in response to their external and internal metabolic state. This review first discusses theoretical works which provide mechanistic insights and design choices for dynamic control systems including two-stage, continuous, and population behavior control strategies. Next, we summarize molecular mechanisms for various sensors and actuators which enable dynamic metabolic control in microbial systems. Finally, important applications of dynamic control to the production of several metabolite products are highlighted, including fatty acids, aromatics, and terpene compounds. Altogether, this review provides a comprehensive overview of the progress, advances, and prospects in the design of dynamic control systems for improved titer, rate, and yield metrics in metabolic engineering.