Thermal imaging of dust hiding the black hole in NGC 1068.

In the widely accepted 'unified model'1 solution of the classification puzzle of active galactic nuclei, the orientation of a dusty accretion torus around the central black hole dominates their appearance. In 'type-1' systems, the bright nucleus is visible at the centre of a face-on torus. In 'type-2' systems the thick, nearly edge-on torus hides the central engine. Later studies suggested evolutionary effects2 and added dusty clumps and polar winds3 but left the basic picture intact. However, recent high-resolution images4 of the archetypal type-2 galaxy NGC 10685,6, suggested a more radical revision. The images displayed a ring-like emission feature that was proposed to be hot dust surrounding the black hole at the radius where the radiation from the central engine evaporates the dust. That ring is too thin and too far tilted from edge-on to hide the central engine, and ad hoc foreground extinction is needed to explain the type-2 classification. These images quickly generated reinterpretations of the dichotomy between types 1 and 27,8. Here we present new multi-band mid-infrared images of NGC 1068 that detail the dust temperature distribution and reaffirm the original model. Combined with radio data (J.F.G. and C.M.V.I., manuscript in preparation), our maps locate the central engine that is below the previously reported ring and obscured by a thick, nearly edge-on disk, as predicted by the unified model. We also identify emission from polar flows and absorbing dust that is mineralogically distinct from that towards the Milky Way centre.

Bioaccumulation of polycyclic aromatic hydrocarbons and microbiota dynamics across developmental stages of the Asian tiger mosquito, Aedes albopictus exposed to urban pollutants.

Aedes albopictus mosquitoes face numerous anthropic stressors in urban areas. These xenobiotics not only impact mosquito physiology but also shape the composition of their microbiota, which play important roles in host physiological traits. Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental pollutants known to alter mosquito metabolism, but no studies have yet investigated their impact on microbiota. Using a bespoke indoor mesocosm tailored for Ae. albopictus mosquitoes, we investigated the dynamics of bacterial communities in both mosquitoes and their larval breeding sites following chronic exposure to a cocktail of PAHs consisting of benzo[a]pyrene, benz[a]anthracene, chrysene and benzo[b]fluoranthene. Our findings showed that PAHs have a stage-specific effect on mosquito microbiota, with a higher impact in larvae than in adults, contributing to 12.5 % and 4.5 % of the PAHs-induced variations, respectively. The presence of PAHs in the treated mesocosm led to the enrichment of bacterial families and genera known for their ability to catabolize PAHs, such as Comamonadaceae and Raoultella (increasing from 19 % to 30 % and from 1.2 % to 5.6 %, respectively). Conversely, prevalent taxa found in mosquito microbiota like Wolbachia and Cedecea exhibited a reduction (decreasing from 4 % to 0.8 % and from 12.8 % to 6.4 %, respectively). This reduction could be attributed to the competitive advantage gained by PAH-degrading taxa, or it could reflect a direct sensitivity to PAH exposure. Overall, this indicates a shift in microbiota composition favoring bacteria that can thrive in a PAH-contaminated environment. PAHs persisted in the water of breeding sites only the first 45 days of the experiment. Benzo[a]pyrene and benzo[b]fluoranthene were more susceptible to bioaccumulation in larval tissues over time. Overall, this study enhances our understanding of the impact of pollution on mosquitoes and could facilitate future research on the importance of symbiosis in urban-dwelling insect disease vectors. Given the recent advancements in the generation of axenic (microbe-free) and gnotobiotic (mosquitoes with a defined or specific microbiota) mosquitoes, further studies are needed to explore how changes in microbiota composition could influence mosquito responses to pollution, particularly in relation to host fitness, immunity, and vector competence.

Impact of Human Activities on Disease-Spreading Mosquitoes in Urban Areas.

Urbanization is one of the leading global trends of the twenty-first century that has a significant impact on health. Among health challenges caused by urbanization, the relationship of urbanization between emergence and the spread of mosquito-borne infectious diseases (MBIDs) is a great public health concern. Urbanization processes encompass social, economic, and environmental changes that directly impact the biology of mosquito species. In particular, urbanized areas experience higher temperatures and pollution levels than outlying areas but also favor the development of infrastructures and objects that are favorable to mosquito development. All these modifications may influence mosquito life history traits and their ability to transmit diseases. This review aimed to summarize the impact of urbanization on mosquito spreading in urban areas and the risk associated with the emergence of MBIDs. Moreover, mosquitoes are considered as holobionts, as evidenced by numerous studies highlighting the role of mosquito-microbiota interactions in mosquito biology. Taking into account this new paradigm, this review also represents an initial synthesis on how human-driven transformations impact microbial communities in larval habitats and further interfere with mosquito behavior and life cycle in urban areas.

Pollution gradients shape microbial communities associated with Ae. albopictus larval habitats in urban community gardens.

The Asian tiger mosquito Aedes albopictus is well adapted to urban environments and takes advantage of the artificial containers that proliferate in anthropized landscapes. Little is known about the physicochemical, pollutant, and microbiota compositions of Ae. albopictus-colonized aquatic habitats and whether these properties differ with noncolonized habitats. We specifically addressed this question in French community gardens by investigating whether pollution gradients (characterized either by water physicochemical properties combined with pollution variables or by the presence of organic molecules in water) influence water microbial composition and then the presence/absence of Ae. albopictus mosquitoes. Interestingly, we showed that the physicochemical and microbial compositions of noncolonized and colonized waters did not significantly differ, with the exception of N2O and CH4 concentrations, which were higher in noncolonized water samples. Moreover, the microbial composition of larval habitats covaried differentially along the pollution gradients according to colonization status. This study opens new avenues on the impact of pollution on mosquito habitats in urban areas and raises questions on the influence of biotic and abiotic interactions on adult life-history traits and their ability to transmit pathogens to humans.

Reciprocal interactions between anthropogenic stressors and insect microbiota.

Insects play many important roles in nature due to their diversity, ecological role, and impact on agriculture or human health. They are directly influenced by environmental changes and in particular anthropic activities that constitute an important driver of change in the environmental characteristics. Insects face numerous anthropogenic stressors and have evolved various detoxication mechanisms to survive and/or resist to these compounds. Recent studies highligted the pressure exerted by xenobiotics on insect life-cycle and the important role of insect-associated bacterial microbiota in the insect responses to environmental changes. Stressor exposure can have various impacts on the composition and structure of insect microbiota that in turn may influence insect biology. Moreover, bacterial communities associated with insects can be directly or indirectly involved in detoxification processes with the selection of certain microorganisms capable of degrading xenobiotics. Further studies are needed to assess the role of insect-associated microbiota as key contributor to the xenobiotic metabolism and thus as a driver for insect adaptation to polluted habitats.