FUNCTIONAL AND COMPARATIVE MORPHOLOGY OF THE NASAL CAVITY IN PHYLLOSTOMID BATS

The functional morphology and evolution of the nasal cavity is poorly understood. The New World Leaf-nosed bats of the family Phyllostomidae are an excellent group of mammals in which to study the evolution of the nose and nasal cavity. Phyllostomids span a wide dietary diversity, which is correlated both with the shape of the rostrum as well as with reliance on olfaction, one of the key functions mediated by the nose and the focus of my dissertation. How does dietary diversity relate to differences in the olfactory anatomy of phyllostomids? I examined three neurological features thought to relate to olfactory capability, with my hypothesis being that fruit-and nectar-feeding bats rely more on olfaction than insect-feeders. I expected that fruit- and nectar-feeders would have relatively greater numbers of the three neuronal measures that I selected compared to insect-feeders. My results mostly supported this prediction, lending support to the basic idea that bats with different diets rely on olfaction to different degrees. To sense odors in the environment, incoming air loaded with odorant molecules must make its way to the back of the nasal cavity, where the olfactory epithelium is located. Do bats with different diets differ in terms of olfactory airflow? In this part of my dissertation, I first performed a computer modeling experiment that tested the hypothesis that the size of the olfactory recess (a key feature of many keen-smelling mammals) relates to differences in important aspects of olfactory airflow. I found that, all else being equal, a larger olfactory recess improves olfactory airflow. Next I performed a comparative study on six species of bats with different diets, expecting to find differences in patterns and rates of olfactory airflow. Instead I found relatively little variation in all of the measured parameters across the species I selected. These results suggest that the morphology of the nasal cavity may not be under strong selective pressure to accommodate different demands on the olfactory system. Investigating this idea more fully, and its consequences for the evolution of the nose and of the skull more broadly, would be an exciting avenue for future research

Structural and functional analysis of pathogenicity factors of Listeria monocytogenes and Staphylococcus aureus

Das Humanpathogen Listeria monocytogenes verursacht die seltene, jedoch lebensgefährliche Infektionskrankheit Listeriose. Eine große Anzahl der bekannten listeriellen Pathogenitätsfaktoren wird von einem einzigen Transkriptionsfaktor (PrfA) reguliert, der zur Crp/Fnr-Familie der bakteriellen Transkriptionsfaktoren gehört. Die Kristallstrukturen von PrfA und einer konstitutiv aktiven Mutante PrfAG145S konnten erfolgreich gelöst werden. Durch den strukturellen Vergleich konnte gezeigt werden, dass die Mutation G145S dramatische strukturelle Änderungen in PrfA auslöst, die insbesondere das HTH-Motiv betreffen. Das HTH-Motiv von PrfAG145S nimmt dabei überraschenderweise eine Konformation an, die dem des cAMP-induzierten, insbesondere dem des DNA-gebundenen Crp entspricht. Desweiteren konnte ein Tunnel in der PrfA-Struktur detektiert werden, der einen kleinen, teilweise hydrophoben Effektor als putativen Kofaktor binden könnte. Mittels Oberflächenplasmonresonanz-Spektroskopie wurden DNA-Bindungsaffinitäten für PrfA ermittelt. Zur detaillierten Analyse der Interaktion von PrfA mit DNA wurden Kokristallisationsversuche von PrfA mit unterschiedlichen Oligonukleotiden durchgeführt. Die ADP-Ribosylierung ist ein wichtiger Prozess, bei dem pathogene Organismen eukaryotische Proteine posttranslational modifizieren. Vor kurzem wurde in Staphylococcus aureus das Exoenzym C3stau2 entdeckt, das zur Familie der C3-ähnlichen ADP-Ribosyltransferasen gehört. Im Gegensatz zu C3bot1, dem Hauptrepräsentanten dieser Familie aus Clostridium botulinum, ADP-ribosyliert C3stau2 neben RhoA, -B und -C auch RhoE und Rnd3, die sich funktionell von den anderen GTPasen unterscheiden. Die Kristallstruktur von C3stau2 wurde erfolgreich gelöst. Dabei stellte sich heraus, dass C3stau2 strukturelle Ähnlichkeiten zu C3bot1 aufweist. Um die erweiterte Substratspezifität von C3stau2 im Detail untersuchen zu können, sollte der Komplex aus C3stau2 und RhoA kristallisiert und strukturell aufgeklärt werden.The human pathogen Listeria monocytogenes causes listeriosis, a serious bacterial infection in humans. The majority of the known pathogenicity factors is regulated by a single transcription factor (PrfA), a member of the Crp/Fnr family of bacterial transcription factors. The crystal structures of PrfA and that of the constitutively active mutant PrfAG145S were solved successfully. The mutation is found to induce dramatic conformational changes especially as regards the helix-turn-helix (HTH) motif, required for DNA-binding. The HTH motif of PrfAG145S is surprisingly similar to that of Cap, the cAMP-activated catabolite gene activator protein, in its DNA-binding conformation. The structure of PrfA, furthermore, reveals a distinct tunnel sufficiently wide to accommodate a small, partly hydrophobe effector that could act as a putative cofactor of PrfA. Quantitative DNA-binding studies were done with surface plasmon resonance spectroscopy. To investigate PrfA-DNA-interaction in detail, cocrystallization experiments with different oligonucleotides were done. ADP-ribosylation is an important posttranslational modification of eukaryotic proteins in pathogenic mechanisms. Recently, in Staphylococcus aureus the exoenzyme C3stau2 was identified, a member of the C3-like ADP-ribosyltranferases (ADP-RT). In contrast to C3bot1, the prototype of the C3-like ADP-RT, C3stau2 modifies in addition to RhoA, -B and -C the GTPases RhoE and Rnd3 that functionally differ from other GTPases. Here we present the crystal structure of C3stau2. As expected the structure of C3stau2 shows strong structural similarity with that of C3bot. To investigate the additional substrate specificity of C3stau2 in detail, crystallization of the complex of C3stau2 and RhoA was done

Roosting Ecology and the Evolution of Pelage Markings in Bats

Multiple lineages of bats have evolved striking facial and body pelage makings, including spots, stripes and countershading. Although researchers have hypothesized that these markings mainly evolved for crypsis, this idea has never been tested in a quantitative and comparative context. We present the first comparative study integrating data on roosting ecology (roost type and colony size) and pelage coloration patterns across bats, and explore the hypothesis that the evolution of bat pelage markings is associated with roosting ecologies that benefit from crypsis. We find that lineages that roost in the vegetation have evolved pelage markings, especially stripes and neck collars, which may function in crypsis through disruptive coloration and a type of countershading that might be unique to bats. We also demonstrate that lineages that live in larger colonies and are larger in size tend not to have pelage markings, possibly because of reduced predation pressures due to the predator dilution effect and a lower number of potential predators. Although social functions for pelage color patterns are also possible, our work provides strong support for the idea that roosting ecology has driven the evolution of pelage markings in bats

Influence of Dopants on Defect Formation in GaN

Influence of p-dopants (Mg and Be) on the structure of GaN has been studied using Transmission Electron Microscopy (TEM). Bulk GaN:Mg and GaN:Be crystals grown by a high pressure and high temperature process and GaN:Mg grown by metal-organic chemical-vapor deposition (MOCVD) have been studied. Structural dependence on growth polarity was observed in the bulk crystals. Spontaneous ordering in bulk GaN:Mg on c-plane (formation of Mg-rich planar defects with characteristics of inversion domains) was observed for growth in the N to Ga polar direction (N polarity). On the opposite site of the crystal (growth in the Ga to N polar direction) Mg-rich pyramidal defects empty inside (pinholes) were observed. Both these defects were also observed in MOCVD grown crystals. Pyramidal defects were also observed in the bulk GaN:Be crystals

Mapping odorant sensitivities reveals a sparse but structured representation of olfactory chemical space by sensory input to the mouse olfactory bulb

© 2022, Burton et al. This article is distributed under the terms of the Creative Commons Attribution License. https://creativecommons.org/licenses/by/4.0/In olfactory systems, convergence of sensory neurons onto glomeruli generates a map of odorant receptor identity. How glomerular maps relate to sensory space remains unclear. We sought to better characterize this relationship in the mouse olfactory system by defining glomeruli in terms of the odorants to which they are most sensitive. Using high-throughput odorant delivery and ultrasensitive imaging of sensory inputs, we imaged responses to 185 odorants presented at concentrations determined to activate only one or a few glomeruli across the dorsal olfactory bulb. The resulting datasets defined the tuning properties of glomeruli - and, by inference, their cognate odorant receptors - in a low-concentration regime, and yielded consensus maps of glomerular sensitivity across a wide range of chemical space. Glomeruli were extremely narrowly tuned, with ~25% responding to only one odorant, and extremely sensitive, responding to their effective odorants at sub-picomolar to nanomolar concentrations. Such narrow tuning in this concentration regime allowed for reliable functional identification of many glomeruli based on a single diagnostic odorant. At the same time, the response spectra of glomeruli responding to multiple odorants was best predicted by straightforward odorant structural features, and glomeruli sensitive to distinct odorants with common structural features were spatially clustered. These results define an underlying structure to the primary representation of sensory space by the mouse olfactory system.Peer reviewe

Molecular basis of halorespiration control by CprK, a CRP-FNR type transcriptional regulator

Certain bacteria are able to conserve energy via the reductive dehalogenation of halo-organic compounds in a respiration-type metabolism. The transcriptional regulator CprK from Desulfitobacterium spp. induces expression of halorespiratory genes upon binding of o-chlorophenol ligands and is reversibly inactivated by oxygen through disulphide bond formation. We report crystal structures of D. hafniense CprK in the ligand-free (both oxidation states), ligand-bound (reduced) and DNA-bound states, making it the first member of the widespread CRP-FNR superfamily for which a complete structural description of both redox-dependent and allosteric molecular rearrangements is available. In conjunction with kinetic and thermodynamic ligand binding studies, we provide a model for the allosteric mechanisms underpinning transcriptional control. Amino acids that play a key role in this mechanism are not conserved in functionally distinct CRP-FNR members. This suggests that, despite significant structural homology, distinct allosteric mechanisms are used, enabling this protein family to control a very wide range of processes

Molecular basis of halorespiration control by CprK, a CRP-FNR type transcriptional regulator

Certain bacteria are able to conserve energy via the reductive dehalogenation of halo-organic compounds in a respiration-type metabolism. The transcriptional regulator CprK from Desulfitobacterium spp. induces expression of halorespiratory genes upon binding of o-chlorophenol ligands and is reversibly inactivated by oxygen through disulphide bond formation. We report crystal structures of D. hafniense CprK in the ligand-free (both oxidation states), ligand-bound (reduced) and DNA-bound states, making it the first member of the widespread CRP-FNR superfamily for which a complete structural description of both redox-dependent and allosteric molecular rearrangements is available. In conjunction with kinetic and thermodynamic ligand binding studies, we provide a model for the allosteric mechanisms underpinning transcriptional control. Amino acids that play a key role in this mechanism are not conserved in functionally distinct CRP-FNR members. This suggests that, despite significant structural homology, distinct allosteric mechanisms are used, enabling this protein family to control a very wide range of processes

Temperature effects on an InGaP (GaInP) (55)Fe X-ray photovoltaic cell.

This paper investigates the effects of temperature on an InGaP (GaInP) (55)Fe X-ray photovoltaic cell prototype for a radioisotope microbattery (also called a nuclear microbattery). An In0.5Ga0.5P p-i-n (5 μm i-layer) mesa photodiode was illuminated by a standard 206 MBq (55)Fe radioisotope X-ray source and characterised over the temperature range -20 °C to 100 °C. The electrical power output of the device reached its maximum value of 1.5 pW at a temperature of -20 °C. An open circuit voltage and a short circuit current of 0.82 V and 2.5 pA, respectively, were obtained at -20 °C. While the electrical power output and the open circuit voltage decreased with increasing temperature, an almost flat trend was found for the short circuit current. The cell conversion efficiency decreased from 2.1% at -20 °C to 0.7% at 100 °C

Comparison of widely used Listeria monocytogenes strains EGD, 10403S, and EGD-e highlights genomic differences underlying variations in pathogenicity

For nearly 3 decades, listeriologists and immunologists have used mainly three strains of the same serovar (1/2a) to analyze the virulence of the bacterial pathogen Listeria monocytogenes. The genomes of two of these strains, EGD-e and 10403S, were released in 2001 and 2008, respectively. Here we report the genome sequence of the third reference strain, EGD, and extensive genomic and phenotypic comparisons of the three strains. Strikingly, EGD-e is genetically highly distinct from EGD (29,016 single nucleotide polymorphisms [SNPs]) and 10403S (30,296 SNPs), and is more related to serovar 1/2c than 1/2a strains. We also found that while EGD and 10403S strains are genetically very close (317 SNPs), EGD has a point mutation in the transcriptional regulator PrfA (PrfA*), leading to constitutive expression of several major virulence genes. We generated an EGD-e PrfA* mutant and showed that EGD behaves like this strain in vitro, with slower growth in broth and higher invasiveness in human cells than those of EGD-e and 10403S. In contrast, bacterial counts in blood, liver, and spleen during infection in mice revealed that EGD and 10403S are less virulent than EGD-e, which is itself less virulent than EGD-e PrfA*. Thus, constitutive expression of PrfA-regulated virulence genes does not appear to provide a significant advantage to the EGD strain during infection in vivo, highlighting the fact that in vitro invasion assays are not sufficient for evaluating the pathogenic potential of L. monocytogenes strains. Together, our results pave the way for deciphering unexplained differences or discrepancies in experiments using different L. monocytogenes strainsOver the past 3 decades, Listeria has become a model organism for host-pathogen interactions, leading to critical discoveries in a broad range of fields, including bacterial gene regulation, cell biology, and bacterial pathophysiology. Scientists studying Listeria use primarily three pathogenic strains: EGD, EGD-e, and 10403S. Despite many studies on EGD, it is the only one of the three strains whose genome has not been sequenced. Here we report the sequence of its genome and a series of important genomic and phenotypic differences between the three strains, in particular, a critical mutation in EGD’s PrfA, the main regulator of Listeria virulence. Our results show that the three strains display differences which may play an important role in the virulence differences observed between the strains. Our findings will be of critical relevance to listeriologists and immunologists who have used or may use Listeria as a tool to study the pathophysiology of listeriosis and immune responsesThis work received financial support from the European Research Council (advanced grant 233348), the French Agence Nationale de la Recherche (grants BACNET 10-BINF-02-01, IBEID ANR-10-LABX-62-01, and ERA-NET ANR-2010-PATH), the Institut Pasteur, the Institut National de la Santé et de la Recherche Médicale, and the Institut National de la Recherche Agronomique. A.K. is a recipient of a scholarship from the Pasteur-Paris University International Doctoral Program/Institut Carnot Maladies Infectieuse