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"Scott, John"
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Wastewater treatment alters microbial colonization of microplastics
Microplastics are ubiquitous contaminants in aquatic habitats globally, and wastewater treatment plants (WWTPs) are point sources of microplastics. Within aquatic habitats microplastics are colonized by microbial biofilms, which can include pathogenic taxa and taxa associated with plastic breakdown. Microplastics enter WWTPs in sewage and exit in sludge or effluent, but the role that WWTPs play in establishing or modifying microplastic bacterial assemblages is unknown. We analyzed microplastics and associated biofilms in raw sewage, effluent water, and sludge from two WWTPs. Both plants retained >99% of influent microplastics in sludge, and sludge microplastics showed higher bacterial species richness and higher abundance of taxa associated with bioflocculation (e.g. Xanthomonas ) than influent microplastics, suggesting that colonization of microplastics within the WWTP may play a role in retention. Microplastics in WWTP effluent included significantly lower abundances of some potentially pathogenic bacterial taxa (e.g. Campylobacteraceae ) compared to influent microplastics; however, other potentially pathogenic taxa (e.g. Acinetobacter ) remained abundant on effluent microplastics, and several taxa linked to plastic breakdown (e.g. Klebsiella , Pseudomonas , and Sphingomonas ) were significantly more abundant on effluent compared to influent microplastics. These results indicate that diverse bacterial assemblages colonize microplastics within sewage and that WWTPs can play a significant role in modifying the microplastic-associated assemblages, which may affect the fate of microplastics within the WWTPs and the environment.
Journal Article
Social network analysis: developments, advances, and prospects
This paper reviews the development of social network analysis and examines its major areas of application in sociology. Current developments, including those from outside the social sciences, are examined and their prospects for advances in substantive knowledge are considered. A concluding section looks at the implications of data mining techniques and highlights the need for interdisciplinary cooperation if significant work is to ensue.
Journal Article
A world in emergence : cities and regions in the 21st century
Beginning with the recent history of capitalism and urbanization and moving into a thorough and complex discussion of the modern city, this book outlines the dynamics of what the author calls the third wave of urbanization, characterized by global capitalism's increasing turn to forms of production revolving around technology-intensive artifacts, financial services, and creative commodities such as film, music, and fashion. The author explores how this shift toward a cognitive and cultural economy has caused dramatic changes in the modern economic landscape in general and in the form and function of world cities in particular. Armed with cutting-edge research and decades of expertise, Allen J. Scott breaks new ground in identifying and explaining how the cities of the past are being reshaped into a complex system of global economic spaces marked by intense relationships of competition and cooperation.
Book
Cell Signaling in Space and Time: Where Proteins Come Together and When They're Apart
Signal transduction can be defined as the coordinated relay of messages derived from extracellular cues to intracellular effectors. More simply put, information received on the cell surface is processed across the plasma membrane and transmitted to intracellular targets. This requires that the activators, effectors, enzymes, and substrates that respond to cellular signals come together when they need to.
Journal Article
The Tomato Yellow Leaf Curl Virus Resistance Genes Ty-1 and Ty-3 Are Allelic and Code for DFDGD-Class RNA–Dependent RNA Polymerases
Tomato Yellow Leaf Curl Virus Disease incited by Tomato yellow leaf curl virus (TYLCV) causes huge losses in tomato production worldwide and is caused by different related begomovirus species. Breeding for TYLCV resistance has been based on the introgression of multiple resistance genes originating from several wild tomato species. In this study we have fine-mapped the widely used Solanum chilense-derived Ty-1 and Ty-3 genes by screening nearly 12,000 plants for recombination events and generating recombinant inbred lines. Multiple molecular markers were developed and used in combination with disease tests to fine-map the genes to a small genomic region (approximately 70 kb). Using a Tobacco Rattle Virus-Virus Induced Gene Silencing approach, the resistance gene was identified. It is shown that Ty-1 and Ty-3 are allelic and that they code for a RNA-dependent RNA polymerase (RDR) belonging to the RDRγ type, which has an atypical DFDGD motif in the catalytic domain. In contrast to the RDRα type, characterized by a catalytic DLDGD motif, no clear function has yet been described for the RDRγ type, and thus the Ty-1/Ty-3 gene unveils a completely new class of resistance gene. Although speculative, the resistance mechanism of Ty-1/Ty-3 and its specificity towards TYLCV are discussed in light of the function of the related RDRα class in the amplification of the RNAi response in plants and transcriptional silencing of geminiviruses in plants.
Journal Article
Signalling scaffolds and local organization of cellular behaviour
Key Points
Scaffold proteins are non-catalytic organizational elements that focus enzyme activity by holding members of a signal transduction cascade in place. They confer bidirectional control on cellular processes through the simultaneous recruitment of signal transduction and signal termination enzymes.
Rather than functioning enzymatically, scaffolds formed by pseudokinases and pseudophosphatases can function as allosteric modulators of other signalling enzymes.
A-kinase anchor proteins (AKAPs) constrain second-messenger-responsive enzymes, such as protein kinase A, in customized macromolecular units. AKAPs are dynamic participants in local signalling, in part owing to their flexibility in structure, transient interactions and combinatorial assembly of binding partners.
Protein scaffolds can also be organized around signal termination enzymes that attenuate signalling or promote the degradation of key enzymes. Three examples of this are the scaffolds that target phosphatases, those that control protein ubiquitylation and those that control acetylation and deacetylation.
Covalent modification of a scaffold protein can determine which binding partners are included in the complex and thus provide alternative functionality. As a result, several scaffold proteins have been identified as ultra-sensitive switches that toggle between opposing cellular processes.
Recent technical advances have shown that scaffold proteins can hold members of a signal transduction cascade in place, focus enzyme activity at a particular site of action and/or provide a structural platform for the recruitment of signal transduction and signal termination enzymes.
Cellular responses to environmental cues involve the mobilization of GTPases, protein kinases and phosphoprotein phosphatases. The spatial organization of these signalling enzymes by scaffold proteins helps to guide the flow of molecular information. Allosteric modulation of scaffolded enzymes can alter their catalytic activity or sensitivity to second messengers in a manner that augments, insulates or terminates local cellular events. This Review examines the features of scaffold proteins and highlights examples of locally organized groups of signalling enzymes that drive essential physiological processes, including hormone action, heart rate, cell division, organelle movement and synaptic transmission.
Journal Article