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Pseudomonad reverse carbon catabolite repression, interspecies metabolite exchange, and consortial division of labor
Microorganisms acquire energy and nutrients from dynamic environments, where substrates vary in both type and abundance. The regulatory system responsible for prioritizing preferred substrates is known as carbon catabolite repression (CCR). Two broad classes of CCR have been documented in the literature. The best described CCR strategy, referred to here as classic CCR (cCCR), has been experimentally and theoretically studied using model organisms such as
Escherichia coli
. cCCR phenotypes are often used to generalize universal strategies for fitness, sometimes incorrectly. For instance, extremely competitive microorganisms, such as Pseudomonads, which arguably have broader global distributions than
E. coli
, have achieved their success using metabolic strategies that are nearly opposite of cCCR. These organisms utilize a CCR strategy termed ‘reverse CCR’ (rCCR), because the order of preferred substrates is nearly reverse that of cCCR. rCCR phenotypes prefer organic acids over glucose, may or may not select preferred substrates to optimize growth rates, and do not allocate intracellular resources in a manner that produces an overflow metabolism. cCCR and rCCR have traditionally been interpreted from the perspective of monocultures, even though most microorganisms live in consortia. Here, we review the basic tenets of the two CCR strategies and consider these phenotypes from the perspective of resource acquisition in consortia, a scenario that surely influenced the evolution of cCCR and rCCR. For instance, cCCR and rCCR metabolism are near mirror images of each other; when considered from a consortium basis, the complementary properties of the two strategies can mitigate direct competition for energy and nutrients and instead establish cooperative division of labor.
Journal Article
The Return of the Repressed
Can purely psychological trauma lead to a complete blockage of autobiographical memories? This long-standing question about the existence of repressed memories has been at the heart of one of the most heated debates in modern psychology. These so-called memory wars originated in the 1990s, and many scholars have assumed that they are over. We demonstrate that this assumption is incorrect and that the controversial issue of repressed memories is alive and well and may even be on the rise. We review converging research and data from legal cases indicating that the topic of repressed memories remains active in clinical, legal, and academic settings. We show that the belief in repressed memories occurs on a nontrivial scale (58%) and appears to have increased among clinical psychologists since the 1990s. We also demonstrate that the scientifically controversial concept of dissociative amnesia, which we argue is a substitute term for memory repression, has gained in popularity. Finally, we review work on the adverse side effects of certain psychotherapeutic techniques, some of which may be linked to the recovery of repressed memories. The memory wars have not vanished. They have continued to endure and contribute to potentially damaging consequences in clinical, legal, and academic contexts.
Journal Article
The Changing Space for NGOs
In this introductory essay to the special issue on civil society in authoritarian and hybrid regimes, we review core themes in the growing literature on shrinking or closing space for civil society. We discuss the role of civil society organizations (CSOs) as agents of democratization and note the emergence of dual, at times apparently conflicting policy postures within authoritarian regimes (restriction and repression for some CSOs vs. financial support and opportunities for collaboration for others). We posit that different conceptual perspectives applied to civil society can help account for the duality of authoritarian postures and examine repercussions for three key subgroups of CSOs: claims-making (or advocacy) NGOs, nonprofit service providers and regime-loyal NGOs supporting often populist and nationalist discourses.
Journal Article
p53 cooperates with DNA methylation and a suicidal interferon response to maintain epigenetic silencing of repeats and noncoding RNAs
Large parts of mammalian genomes are transcriptionally inactive and enriched with various classes of interspersed and tandem repeats. Here we show that the tumor suppressor protein p53 cooperates with DNA methylation to maintain silencing of a large portion of the mouse genome. Massive transcription of major classes of short, interspersed nuclear elements (SINEs) B1 and B2, both strands of near-centromeric satellite DNAs consisting of tandem repeats, and multiple species of noncoding RNAs was observed in p53-deficient but not in p53 wild-type mouse fibroblasts treated with the DNA demethylating agent 5-aza-2’-deoxycytidine. The abundance of these transcripts exceeded the level of β-actin mRNA by more than 150-fold. Accumulation of these transcripts, which are capable of forming double-stranded RNA (dsRNA), was accompanied by a strong, endogenous, apoptosis-inducing type I IFN response. This phenomenon, which we named “TRAIN” (for “transcription of repeats activates interferon”), was observed in spontaneous tumors in two models of cancer-prone mice, presumably reflecting naturally occurring DNA hypomethylation and p53 inactivation in cancer. These observations suggest that p53 and IFN cooperate to prevent accumulation of cells with activated repeats and provide a plausible explanation for the deregulation of IFN function frequently seen in tumors. Overall, this work reveals roles for p53 and IFN that are key for genetic stability and therefore relevant to both tumorigenesis and the evolution of species.
Journal Article
To Defend This Sunrise
To Defend this Sunrise examines how black women on the
Caribbean coast of Nicaragua engage in regional, national, and
transnational modes of activism to remap the nation's racial order
under conditions of increasing economic precarity and autocracy.
The book considers how, since the 19th century, black women
activists have resisted historical and contemporary patterns of
racialized state violence, economic exclusion, territorial
dispossession, and political repression. Specifically, it explores
how the new Sandinista state under Daniel Ortega and Rosario
Murillo has utilized multicultural rhetoric as a mode of political,
economic, and territorial dispossession. In the face of the
Sandinista state's co-optation of multicultural discourse and
growing authoritarianism, black communities have had to recalibrate
their activist strategies and modes of critique to resist these new
forms of \"multicultural dispossession.\" This concept describes the
ways that state actors and institutions drain multiculturalism of
its radical, transformative potential by espousing the rhetoric of
democratic recognition while simultaneously supporting illiberal
practices and policies that undermine black political demands and
weaken the legal frameworks that provide the basis for the claims
of these activists against the state.
eBook
Carbon Catabolite Repression in Filamentous Fungi
Carbon Catabolite Repression (CCR) has fascinated scientists and researchers around the globe for the past few decades. This important mechanism allows preferential utilization of an energy-efficient and readily available carbon source over relatively less easily accessible carbon sources. This mechanism helps microorganisms to obtain maximum amount of glucose in order to keep pace with their metabolism. Microorganisms assimilate glucose and highly favorable sugars before switching to less-favored sources of carbon such as organic acids and alcohols. In CCR of filamentous fungi, CreA acts as a transcription factor, which is regulated to some extent by ubiquitination. CreD-HulA ubiquitination ligase complex helps in CreA ubiquitination, while CreB-CreC deubiquitination (DUB) complex removes ubiquitin from CreA, which causes its activation. CCR of fungi also involves some very crucial elements such as Hexokinases, cAMP, Protein Kinase (PKA), Ras proteins, G protein-coupled receptor (GPCR), Adenylate cyclase, RcoA and SnfA. Thorough study of molecular mechanism of CCR is important for understanding growth, conidiation, virulence and survival of filamentous fungi. This review is a comprehensive revision of the regulation of CCR in filamentous fungi as well as an updated summary of key regulators, regulation of different CCR-dependent mechanisms and its impact on various physical characteristics of filamentous fungi.
Journal Article
Focal Points, Dissident Calendars, and Preemptive Repression
This article explains temporal variation in repression as a function of the “dissident calendar,” the set of events that serve as natural focal points for coordination. The core argument is that regimes can anticipate the events that create these focal points and engage in preemptive repression to survive their passing. This dynamic produces predictable, often cyclical patterns in repression. An analysis of dissident detentions in China from 1998 to 2014 shows that “focal events” alone appear to be responsible for more than 20 percent of dissident detentions over the analysis period. Such detentions tend to be shorter and rely less on formal criminal procedures, suggesting a “catch-and-release” dynamic. Additional analysis of detentions in Tibet shows how the calendar may vary by issue or group.
Journal Article
State Repression and Nonviolent Resistance
In this article, we review decades of research on state repression and nonviolent resistance. We argue that these two research programs have converged around six consensus findings. We also highlight several areas of divergence, where greater synthesis between the research on state repression and nonviolent resistance might prove useful. We draw attention to remaining controversies surrounding the association between state repression and nonviolent resistance—particularly regarding different theoretical assumptions about structure, agency, and strategic choice; measurement challenges for both repression and dissent; methodological challenges regarding endogeneity, multicausality, and equifinality; and moral hazards associated with the study of nonviolent resistance and the effectiveness of repression. We conclude by highlighting some productive ways forward.
Journal Article