Innate Immune Recognition of Yersinia pseudotuberculosis Type III Secretion

Specialized protein translocation systems are used by many bacterial pathogens to deliver effector proteins into host cells that interfere with normal cellular functions. How the host immune system recognizes and responds to this intrusive event is not understood. To address these questions, we determined the mammalian cellular response to the virulence-associated type III secretion system (T3SS) of the human pathogen Yersinia pseudotuberculosis. We found that macrophages devoid of Toll-like receptor (TLR) signaling regulate expression of 266 genes following recognition of the Y. pseudotuberculosis T3SS. This analysis revealed two temporally distinct responses that could be separated into activation of NFκB- and type I IFN-regulated genes. Extracellular bacteria were capable of triggering these signaling events, as inhibition of bacterial uptake had no effect on the ensuing innate immune response. The cytosolic peptidoglycan sensors Nod1 and Nod2 and the inflammasome component caspase-1 were not involved in NFκB activation following recognition of the Y. pseudotuberculosis T3SS. However, caspase-1 was required for secretion of the inflammatory cytokine IL-1β in response to T3SS-positive Y. pseudotuberculosis. In order to characterize the bacterial requirements for induction of this novel TLR-, Nod1/2-, and caspase-1-independent response, we used Y. pseudotuberculosis strains lacking specific components of the T3SS. Formation of a functional T3SS pore was required, as bacteria expressing a secretion needle, but lacking the pore-forming proteins YopB or YopD, did not trigger these signaling events. However, nonspecific membrane disruption could not recapitulate the NFκB signaling triggered by Y. pseudotuberculosis expressing a functional T3SS pore. Although host cell recognition of the T3SS did not require known translocated substrates, the ensuing response could be modulated by effectors such as YopJ and YopT, as YopT amplified the response, while YopJ dampened it. Collectively, these data suggest that combined recognition of the T3SS pore and YopBD-mediated delivery of immune activating ligands into the host cytosol informs the host cell of pathogenic challenge. This leads to a unique, multifactorial response distinct from the canonical immune response to a bacterium lacking a T3SS

Urban Agriculture Oriented towards Self-Supply, Social and Commercial Purpose: A Typology

Urban agriculture, a dynamic multifunctional phenomenon, affects the spatial diversification of urban land use, its valorization and its governance. Literature acknowledges its contribution to the development of sustainable cities. The dimension and extent of this contribution depends significantly on the particular form and function of urban agriculture. However, the complexity of interests and dimensions is insufficiently covered by theory. This paper proposes a typology for urban agriculture, supporting both theory building and practical decision processes. We reviewed and mapped the diversity of the types of agriculture found along three beneficial dimensions (self-supply, socio-cultural, commercial) for product distribution scale and actors. We distinguish between ideal types, subtypes and mixed types. Our intention is to include a dynamic perspective in the typology of urban agricultural land use because transition processes between types are observable due to the existence of complex motivations and influences. In a pilot study of 52 urban agriculture initiatives in Germany, we tested the validity of the typology and discussed it with stakeholders, proving novelty and relevance for profiling discussions

Contributing to food security in urban areas: differences between urban agriculture and peri-urban agriculture in the Global North

Food security is becoming an increasingly relevant topic in the Global North, especially in urban areas. Because such areas do not always have good access to nutritionally adequate food, the question of how to supply them is an urgent priority in order to maintain a healthy population. Urban and peri-urban agriculture, as sources of local fresh food, could play an important role. Whereas some scholars do not differentiate between peri-urban and urban agriculture, seeing them as a single entity, our hypothesis is that they are distinct, and that this has important consequences for food security and other issues. This has knock-on effects for food system planning and has not yet been appropriately analysed. The objectives of this study are to provide a systematic understanding of urban and peri-urban agriculture in the Global North, showing their similarities and differences, and to analyse their impact on urban food security. To this end, an extensive literature review was conducted, resulting in the identification and comparison of their spatial, ecological and socio-economic characteristics. The findings are discussed in terms of their impact on food security in relation to the four levels of the food system: food production, processing, distribution and consumption. The results show that urban and peri-urban agriculture in the Global North indeed differ in most of their characteristics and consequently also in their ability to meet the food needs of urban inhabitants. While urban agriculture still meets food needs mainly at the household level, peri-urban agriculture can provide larger quantities and has broader distribution pathways, giving it a separate status in terms of food security. Nevertheless, both possess (unused) potential, making them valuable for urban food planning, and both face similar threats regarding urbanisation pressures, necessitating adequate planning measures

Effects of consumer-producer interactions in alternative food networks on consumers’ learning about food and agriculture

In the recent literature, Alternative Food Networks (AFN) are discussed as a promising approach, at the urban-rural interface, to meeting the challenges of the current agri-food system. Consumer-producer collaboration is seen as a characteristic feature in this context. What is lacking, however, are general concepts for describing the topics of consumer-producer interactions (CPI). The present study aims (1) to develop an analytical framework relying on six CPI domains and (2) to apply it to investigate CPI effects on consumers’ learning about and appreciation of agriculture. We conducted 26 guided interviews with consumers and producers of the three most frequent AFN types in Germany: community-supported agriculture (CSA), food coops, and self-harvest gardens. The results show that AFN participation enhances consumers’ learning about food (seasonality, cooking/nutrition, housekeeping aspects) and agricultural production (farmers’ perspectives, cultivation). Our results show that consumer’s learning is influenced by certain CPI domains, and each AFN type can be described by distinctive CPI domains. This led to the conclusion that specific AFN types open up specific learning channels and contents, with consumers learning from producers. AFNs at the urban-rural interface exploit knowledge of rurality

Toward Sustainability: Novelties, Areas of Learning and Innovation in Urban Agriculture

Given the search for new solutions to better prepare cities for the future, in recent years, urban agriculture (UA) has gained in relevance. Within the context of UA, innovative organizational and technical approaches are generated and tested. They can be understood as novelties that begin a potential innovation process. This empirical study is based on 17 qualitative interviews in the U.S. (NYC; Philadelphia, PA, USA; Chicago, IL, USA). The aim was to identify: (i) the most relevant areas of learning and innovation; (ii) the drivers of innovation; (iii) the applied novelties and their specific approach to overcoming the perceived obstacles; (iv) the intrinsic challenges that practitioners face in the innovation process; and (v) the novelties’ potential to contribute to sustainability and societal change. As the results of the study demonstrate, learning and innovation in UA occur predominantly in four areas, namely, “financing and funding”, “production, technology and infrastructure”, “markets and demands” and “social acceptance and cultural learning”. The described novelties include approaches to enhance the positive impacts of practicing agriculture within urban areas, and some of them have the potential to contribute to societal change and open up opportunities for social learning processes