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Coordination between cell populations via prevailing metabolic cues has been noted as a promising approach to connect synthetic devices and drive phenotypic or product outcomes. However, there has been little progress in developing ‘controller cells’ to modulate metabolic cues and guide these systems. In this work, we developed ‘controller cells’ that manipulate the molecular connection between cells by modulating the bacterial signal molecule, autoinducer-2, that is secreted as a quorum sensing (QS) signal by many bacterial species. Specifically, we have engineered Escherichia coli to overexpress components responsible for autoinducer uptake (lsrACDB), phosphorylation (lsrK), and degradation (lsrFG), thereby attenuating cell–cell communication among populations. Further, we developed a simple mathematical model that recapitulates experimental data and characterizes the dynamic balance among the various uptake mechanisms. This study revealed two controller ‘knobs’ that serve to increase AI-2 uptake: overexpression of the AI-2 transporter, LsrACDB, which controls removal of extracellular AI-2, and overexpression of the AI-2 kinase, LsrK, which increases the net uptake rate by limiting secretion of AI-2 back into the extracellular environment. We find that the overexpression of lsrACDBFG results in an extraordinarily high AI-2 uptake rate that is capable of completely silencing QS-mediated gene expression among wild-type cells. We demonstrate utility by modulating naturally occurring processes of chemotaxis and biofilm formation. We envision that ‘controller cells’ that modulate bacterial behavior by manipulating molecular communication, will find use in a variety of applications, particularly those employing natural or synthetic bacterial consortia. 相似文献
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Griffiths PE 《Acta biotheoretica》2009,57(1-2):11-32
Dobzhansky argued that biology only makes sense if life on earth has a shared history. But his dictum is often reinterpreted to mean that biology only makes sense in the light of adaptation. Some philosophers of science have argued in this spirit that all work in 'proximal' biosciences such as anatomy, physiology and molecular biology must be framed, at least implicitly, by the selection histories of the organisms under study. Others have denied this and have proposed non-evolutionary ways in which biologists can frame these investigations. This paper argues that an evolutionary perspective is indeed necessary, but that it must be a forward-looking perspective informed by a general understanding of the evolutionary process, not a backward-looking perspective informed by the specific evolutionary history of the species being studied. Interestingly, it turns out that there are aspects of proximal biology that even a creationist cannot study except in the light of a theory of their effect on future evolution. 相似文献
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Biologists rely heavily on the language of information, coding, and transmission that is commonplace in the field of information
theory developed by Claude Shannon, but there is open debate about whether such language is anything more than facile metaphor.
Philosophers of biology have argued that when biologists talk about information in genes and in evolution, they are not talking
about the sort of information that Shannon’s theory addresses. First, philosophers have suggested that Shannon’s theory is
only useful for developing a shallow notion of correlation, the so-called “causal sense” of information. Second, they typically
argue that in genetics and evolutionary biology, information language is used in a “semantic sense,” whereas semantics are
deliberately omitted from Shannon’s theory. Neither critique is well-founded. Here we propose an alternative to the causal
and semantic senses of information: a transmission sense of information, in which an object X conveys information if the function of X is to reduce, by virtue of its sequence properties, uncertainty
on the part of an agent who observes X. The transmission sense not only captures much of what biologists intend when they
talk about information in genes, but also brings Shannon’s theory back to the fore. By taking the viewpoint of a communications
engineer and focusing on the decision problem of how information is to be packaged for transport, this approach resolves several
problems that have plagued the information concept in biology, and highlights a number of important features of the way that
information is encoded, stored, and transmitted as genetic sequence. 相似文献
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Summary Ecologists often standardize data through the use of ratios and indices. Such measures are employed generally to remove a size effect induced by some relatively uniteresting variable. The implications of using the resultant data in correlation and regression analyses are poorly recognized. We show that ratios and indices often provide surprising and spurious results due to their unusual properties. As a solution, we advocate the use of randomization tests to evaluate hypotheses confounded by spurious correlations. In addition, we emphasize that identifying the appropriate null correlation is of utmost importance when statistically evaluating ratios, although this issue is frequently ignored. 相似文献
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Gabriele Alex 《Ethnos》2013,78(4):523-543
In India, touch is a prime marker of status and social relations. Those who are impure are ‘untouchable’,1 but those who are of a relatively higher purity are also, depending on the context, either ‘untouchable’ or ‘touchable’ only under certain fixed rules. In this paper, I will explore the contexts in which body contact and touch can be part of personal relations. I describe how these body contacts signify important social relations and establish community identity. Further, I will analyse how patterns of body contact on the one hand change during childhood, and on the other hand produce changes in the status of a social persona. The last point to be investigated is the meaning of touch as a sign for public representations. 相似文献
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Kenneth Brown 《Ethnos》2013,78(3-4):197-231
This article consists of a critical application of recent theory of nationalism to the unusual case of Mauritius. It is a poly‐ethnic and poly‐religious society whose inhabitants neither share a mythical distant past nor consider themselves culturally identical, but where nation‐building has nevertheless been moderately successful since the late 1960s. Through an examination of the processes of institutional and cultural nation‐building in the island, it is argued that the current Eurocentric view of the nation (notably as a culturally homogeneous imagined community) must be modified to fit cases like this one. Thus, the value of nationalism and nationhood as comparative concepts is questioned. 相似文献
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This paper explains the objectives of organising the symposium ‘The Other North Sea’. A major goal is the submission of the
conclusions and content of this symposium to the North Sea Task Force, an initiative of the Second Conference on the Protection
of the North Sea (London, 1987) which is responsible for preparing a Quality Status Report on the North Sea by mid-1993. The
conclusions and recommendations of the symposium are summarised and presented to the North Sea Task Force in connection with
the preparations for the 1993 Quality Status Report. The paper stresses the need to subdivide the North Sea into areas of
ecological entity and underlines the advantages of using diatom and meiofauna assemblages as indicators for present and past
environmental actors in sediment conditions. A plea is also made for the promotion of research to improve understanding of
disturbance of sensory perception and behaviour as an ecologically relevant early warning signal. The major role of fisheries
in inducing changes of seabird and harbour porpoise populations is highlighted. 相似文献
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《Cell biology international reports》1980,4(12):1081-1090
Two distinct classes of protein referred to as short- and long-lived (Poole and Wibo, 1973) were found in pulse-chased HeLa S-3 and BHK 21/C13 cells. From experiments with pulse times ranging from 1 min to 20 h, a clear inverse correlation emerged between the pulse length and the percentage of protein which was hydrolysed intracellularly in the first h of chase. Using a 5 min pulse labelling with 3H-leucine, cells were either harvested immediately or after a 2 h chase. Approximately 35% of the label incorporated by cells was lost in a 2h chase; however, electrophoretic separation of cytosol and residual cytoplasmic fractions revealed no significant alteration in their protein profiles. The technique of selectively labelling ‘short’ and ‘long-lived’ proteins, which implies qualitative differences between them, is more readily interpreted as an artificial polarisation of a declining statistical probability curve of proteolysis with time which is similar for all nascent proteins. 相似文献
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NK recognition of target structures: is the transferrin receptor the NK target structure? 总被引:3,自引:0,他引:3
R A Newman J F Warner G Dennert 《Journal of immunology (Baltimore, Md. : 1950)》1984,133(4):1841-1845
That the transferrin receptor acts as a target antigen for human NK cells has previously been suggested. In this study we used two models to examine the hypothesis that the transferrin receptor is recognized by NK cells. In the first model, we employed mouse cloned NK cells in conjunction with the species-specific monoclonal antibody R17 217, which binds to the murine transferrin receptor. We show that there is no correlation between the amount of transferrin receptor expressed on targets and the susceptibility of these targets to NK lysis or NK binding in cold target competition assays. In the second model, we used human NK cells and transferrin receptor-positive transformants as targets. These transformants were derived from mouse L cells transfected with human DNA and selected for the presence of human transferrin receptor. Results show that, in contrast to the mouse system, there is a correlation between the expression of the human transferrin receptor on targets and the ability of these targets to competitively inhibit the lysis of K562 by NK cells. However, because inhibition is not complete, other cell surface antigens probably play a role in human NK-target interactions. 相似文献
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Background
Legionella pneumophila is a waterborne pathogen responsible for Legionnaires’ disease, an infection which can lead to potentially fatal pneumonia. After disinfection, L. pneumophila has been detected, like many other bacteria, in a “viable but non culturable” state (VBNC). The physiological significance of the VBNC state is unclear and controversial: it could be an adaptive response favoring long-term survival; or the consequence of cellular deterioration which, despite maintenance of certain features of viable cells, leads to death; or an injured state leading to an artificial loss of culturability during the plating procedure. VBNC cells have been found to be resuscitated by contact with amoebae.Results
We used quantitative microscopic analysis, to investigate this “resuscitation” phenomenon in L. pneumophila in a model involving amending solid plating media with ROS scavengers (pyruvate or glutamate), and co-culture with amoebae. Our results suggest that the restoration observed in the presence of pyruvate and glutamate may be mostly due to the capacity of these molecules to help the injured cells to recover after a stress. We report evidence that this extracellular signal leads to a transition from a not-culturable form to a culturable form of L. pneumophila, providing a technique for recovering virulent and previously uncultivated forms of L. pneumophila.Conclusion
These new media could be used to reduce the risk of underestimation of counts of virulent of L. pneumophila cells in environmental samples. 相似文献18.
Maurer MH 《基因组蛋白质组与生物信息学报(英文版)》2004,2(2):123-131
Whereas genomics describes the study of genome, mainly represented by its gene expression on the DNA or RNA level, the term proteomics denotes the study of the proteome, which is the protein complement encoded by the genome. In recent years, the number of proteomic experiments increased tremendously. While all fields of proteomics have made major technological advances, the biggest step was seen in bioinformatics. Biological information management relies on sequence and structure databases and powerful software tools to translate experimental results into meaningful biological hypotheses and answers. In this resource article, I provide a collection of databases and software available on the Internet that are useful to interpret genomic and proteomic data. The article is a toolbox for researchers who have genomic or proteomic datasets and need to put their findings into a biological context. 相似文献
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