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Cooperatively breeding animals live in social groups in which some individuals help to raise the offspring of others, often at the expense of their own reproduction. Kin selection—when individuals increase their inclusive fitness by aiding genetic relatives—is a powerful explanation for the evolution of cooperative breeding, particularly because most groups consist of family members. However, recent molecular studies have revealed that many cooperative groups also contain unrelated immigrants, and the processes responsible for the formation and maintenance of non-kin coalitions are receiving increasing attention. Here, I provide the first systematic review of group structure for all 213 species of cooperatively breeding birds for which data are available. Although the majority of species (55%) nest in nuclear family groups, cooperative breeding by unrelated individuals is more common than previously recognized: 30% nest in mixed groups of relatives and non-relatives, and 15% nest primarily with non-relatives. Obligate cooperative breeders are far more likely to breed with non-kin than are facultative cooperators, indicating that when constraints on independent breeding are sufficiently severe, the direct benefits of group membership can substitute for potential kin-selected benefits. I review three patterns of dispersal that give rise to social groups with low genetic relatedness, and I discuss the selective pressures that favour the formation of such groups. Although kin selection has undoubtedly been crucial to the origin of most avian social systems, direct benefits have subsequently come to play a predominant role in some societies, allowing cooperation to persist despite low genetic relatedness. 相似文献
104.
Bibi NS Gavara PR Soto Espinosa SL Grasselli M Fernández-Lahore M 《Biotechnology progress》2011,27(5):1329-1338
The preparation of megaporous bodies, with potential applications in biotechnology, was attempted by following several strategies. As a first step, naive and robust scaffolds were produced by polymerization of selected monomers in the presence of a highly soluble cross‐linker agent. Ion‐exchange function was incorporated by particle embedding, direct chemical synthesis, or radiation‐induced grafting. The total ionic capacity of such systems was 1.5 mmol H+/g, 1.4 mmol H+/g, and 17 mmol H+/g, respectively. These values were in agreement with the ability to bind model proteins: observed dynamic binding capacity at 50% breakthrough was ?7.2 mg bovine serum albumin/g, ?7.4 hen egg‐white lysozyme (HEWL) mg/g, and ?108 HEWL mg/g. In the later case, total (static) binding capacity reached 220 mg/g. It was observed that the structure and size of the megapores remained unaffected by the grafting procedure which, however, allowed for the highest protein binding capacity. Lysozyme supported on grafted body showed extensive clarification activity against a Micrococcus lysodekticus suspension in the flow‐through mode, i.e., 90% destruction of suspended microbial cells was obtained with a residence time ≈ 18 min. Both protein capture and biocatalysis applications are conceivable with the 3D‐megaporous materials described in this work. © 2011 American Institute of Chemical Engineers Biotechnol. Prog., 2011 相似文献
105.
During aerobic growth of Escherichia coli, nicotinamide adenine dinucleotide (NADH) can initiate electron transport at either of two sites: Complex I (NDH-1 or NADH:
ubiquinone oxidoreductase) or a single-subunit NADH dehydrogenase (NDH-2). We report evidence for the specific coupling of
malate dehydrogenase to Complex I. Membrane vesicles prepared from wild type cultures retain malate dehydrogenase and are
capable of proton translocation driven by the addition of malate+NAD. This activity was inhibited by capsaicin, an inhibitor
specific to Complex I, and it proceeded with deamino-NAD, a substrate utilized by Complex I, but not by NDH-2. The concentration
of free NADH produced by membrane vesicles supplemented with malate+NAD was estimated to be 1 μM, while the rate of proton translocation due to Complex I was consistent with a some what higher concentration, suggesting
a direct transfer mechanism. This interpretation was supported by competition assays in which inactive mutant forms of malate
dehydrogenase were able to inhibit Complex I activity.
These two lines of evidence indicate that the direct transfer of NADH from malate dehydrogenase to Complex I can occur in
the E. coli system. 相似文献
106.
Jae Yeon Park Yang Hee Kim Andrew Seong Young Je Yoo 《Biotechnology and Bioprocess Engineering》2008,13(4):431-435
An amperometric glucose biosensor was designed for the detection of glucose in blood, urine, beverages, and fermentation systems.
In typical glucose biosensors that employ enzymes, mediators are used for efficient electron transfer between the enzymes
and the electrode. However, some of these mediators are known to be toxic to the enzymes and also must be immobilized on the
surface of the electrode. We propose a mediator-free glucose biosensor that uses a glucose oxidase immobilized on a tin oxide
electrode. Direct electron transfer is possible in this system because the tin oxide has redox properties similar to those
of mediators. The method for immobilization of the glucose oxidase onto the tin oxide is also very simple. Tin oxide was prepared
by the anodization and annealing of pure tin, and this provides a large surface area for the immobilization step because of
its porosity. Glucose oxidase was immobilized onto the tin oxide using the membrane entrapment method. The proposed method
provides a simple process for fabricating the enzyme electrode. Glucose oxidase immobilized onto the tin oxide, prepared in
accordance with this method, has a relatively large current response when comparedto those of other glucose biosensors. The
sensitivity of the biosensor was 19.55 μA/mM, and a linear response was observed between 0∼3 mM glucose. This biosensor demonstrated
good reproducibility and stability. 相似文献
107.
Verena Hiebl Angela Ladurner Simone Latkolik Verena M. Dirsch 《Biotechnology advances》2018,36(6):1657-1698
Nuclear receptors (NRs) represent attractive targets for the treatment of metabolic syndrome-related diseases. In addition, natural products are an interesting pool of potential ligands since they have been refined under evolutionary pressure to interact with proteins or other biological targets.This review aims to briefly summarize current basic knowledge regarding the liver X (LXR) and farnesoid X receptors (FXR) that form permissive heterodimers with retinoid X receptors (RXR). Natural product-based ligands for these receptors are summarized and the potential of LXR, FXR and RXR as targets in precision medicine is discussed. 相似文献
108.
109.
甲烷作为全球第二大温室气体,是典型的可再生清洁能源,也是碳循环中的重要物质组成。大气中约74%的甲烷由产甲烷古菌和其他微生物的互营产生,种间电子传递(interspecies electron transfer, IET)是微生物菌群降低热力学能垒、实现互营产甲烷的核心过程。IET可分为间接种间电子传递(mediated interspecies electron transfer,MIET)和直接种间电子传递(direct interspecies electron transfer, DIET)两种类型,其中MIET依赖氢气、甲酸等载体完成电子的远距离传输,而DIET则依赖导电菌毛、细胞色素c等膜蛋白,通过微生物的直接接触实现电子传递。本文将从IET的研究历程出发,从电子传递机制、微生物种类、生态多样性等方面对微生物互营产甲烷过程中的两种IET类型进行比较,最后对未来待探索的方向进行展望。本综述有助于加深对微生物互营产甲烷过程中IET的理解,为解决由甲烷引发的全球气候变暖等生态问题提供理论支撑。 相似文献
110.
Mechanism of a plastic phenotypic response: predator-induced shell thickening in the intertidal gastropod Littorina obtusata 总被引:1,自引:0,他引:1
Phenotypic plasticity has been the object of considerable interest over the past several decades, but in few cases are mechanisms underlying plastic responses well understood. For example, it is unclear whether predator-induced changes in gastropod shell morphology represent an active physiological response or a by-product of reduced feeding. We address this question by manipulating feeding and growth of intertidal snails, Littorina obtusata, using two approaches: (i) exposure to predation cues from green crabs Carcinus maenas and (ii) reduced food availability, and quantifying growth in shell length, shell mass, and body mass, as well as production of faecal material and shell micro-structural characteristics (mineralogy and organic fraction) after 96 days. We demonstrate that L. obtusata actively increases calcification rate in response to predation threat, and that this response entails energetic and developmental costs. That this induced response is not strictly tied to the animal's behaviour should enhance its evolutionary potential. 相似文献