Monte Carlo Simulation of Age-Dependent Host-Parasite Relations

The death of a biological population is an extreme event which we investigate here for a host-parasitoid system. Our simulations using the Penna ageing model show how biological evolution can ``teach'' the parasitoids to avoid extinction by waiting for the right age of the host. We also show the dependence of extinction time on the population size.Comment: 8 pages including 6 figure

Repatriation of knowledge about insects and types through the DORSA virtual museum (Digital Orthoptera Specimen Access).

DORSA (Digital Orthoptera Specimen Access) ist ein virtuelles Museum, das Informationen über Typus-Exemplare von Orthopteren und andere Belege, welche über die wichtigsten deutschen Museums-Sammlungen verstreut sind, in einer einzigen Datenbank zusammenführt. Etwa 16.000 Individuen-Einträge aus über 4.000 Arten sind über das Internet in der SYSTAX-Datenbank (www.biologie.uni-ulm.de/systax) suchbar. SYSTAX stellt die Daten auch über die GBIF (Global Biodiversity Information Facility)- und BIOCASE (Biological Collection Access Service for Europe)- Portale bereit. Etwa 8.000 Typus-Individuen (davon 2.300 primäre Typen) sind mit über 30.000 Fotos dokumentiert. Die Datenbank enthält ferner 12.000 Tonaufnahmen. Fundortdaten und Verbreitungskarten der gespeicherten Individuen sind ebenfalls abrufbar. Die DORSA-Individuendaten sind reziprok mit dem Orthoptera Species File (OSF) verbunden; dieses bildet zugleich das taxonomische Rückrat für DORSA. Alle DORSA Informationen sind frei über das Internet verfügbar. Auf diese Weise wird das Wissen über die Typus-Individuen, die seit der Kolonialzeit gesammelt worden waren, in die Herkunftsländer repatriiert.StichwörterOrthoptera, DORSA, SYSTAX, OSF, specimen database, type information, virtual museum, repatriation of knowledge.DORSA (Digital Orthoptera Specimen Access) is a virtual museum joining information on Orthoptera types and voucher specimens scattered over the major German museum collections in a single database. Data for about 16,000 specimen records including types and vouchers in over 4,000 species are searchable online via the SYSTAX database (www.biologie.uni-ulm.de/systax) which is linked to both the GBIF (Global Biodiversity Information Facility)- and BIOCASE (Biological Collection Access Service for Europe)- portals. Roughly 8,000 type specimens (with about 2,300 primary types) are documented with over 30,000 images. 12,000 sound files are also available as are geographical information and maps of the specimens in the database. DORSA specimen information is reciprocally linked to the Orthoptera Species File (OSF) which forms the taxonomic backbone for all taxon names used by DORSA. All DORSA data are freely available on the world-wide web. In this way, the knowledge about type specimens collected since colonial times is repatriated to the countries of origin.KeywordsOrthoptera, DORSA, SYSTAX, OSF, specimen database, type information, virtual museum, repatriation of knowledge

Visualizing fusion of pseudotyped HIV-1 particles in real time by live cell microscopy

RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are.Abstract Background Most retroviruses enter their host cells by fusing the viral envelope with the plasma membrane. Although the protein machinery promoting fusion has been characterized extensively, the dynamics of the process are largely unknown. Results We generated human immunodeficiency virus-1 (HIV-1) particles pseudotyped with the envelope (Env) protein of ecotropic murine leukemia virus eMLV to study retrovirus entry at the plasma membrane using live-cell microscopy. This Env protein mediates highly efficient pH independent fusion at the cell surface and can be functionally tagged with a fluorescent protein. To detect fusion events, double labeled particles carrying one fluorophor in Env and the other in the matrix (MA) domain of Gag were generated and characterized. Fusion events were defined as loss of Env signal after virus-cell contact. Single particle tracking of >20,000 individual traces in two color channels recorded 28 events of color separation, where particles lost the Env protein, with the MA layer remaining stable at least for a short period. Fourty-five events were detected where both colors were lost simultaneously. Importantly, the first type of event was never observed when particles were pseudotyped with a non-fusogenic Env. Conclusion These results reveal rapid retroviral fusion at the plasma membrane and permit studies of the immediate post-fusion events.Published versio

From the northern ice shield to the Alpine glaciations

The route of the field trip described in this excursion guide follows a section through Germany from North to South, from the area of the Northern glaciation, to the Alpine glacial advances. It includes several places of historical importance, where milestones in Quaternary research have been achieved in the past, as well as new interesting sites where results of recent research is presented.excursionguid

Dynamics of HIV-1 Assembly and Release

Assembly and release of human immunodeficiency virus (HIV) occur at the plasma membrane of infected cells and are driven by the Gag polyprotein. Previous studies analyzed viral morphogenesis using biochemical methods and static images, while dynamic and kinetic information has been lacking until very recently. Using a combination of wide-field and total internal reflection fluorescence microscopy, we have investigated the assembly and release of fluorescently labeled HIV-1 at the plasma membrane of living cells with high time resolution. Gag assembled into discrete clusters corresponding to single virions. Formation of multiple particles from the same site was rarely observed. Using a photoconvertible fluorescent protein fused to Gag, we determined that assembly was nucleated preferentially by Gag molecules that had recently attached to the plasma membrane or arrived directly from the cytosol. Both membrane-bound and cytosol derived Gag polyproteins contributed to the growing bud. After their initial appearance, assembly sites accumulated at the plasma membrane of individual cells over 1–2 hours. Assembly kinetics were rapid: the number of Gag molecules at a budding site increased, following a saturating exponential with a rate constant of ∼5×10−3 s−1, corresponding to 8–9 min for 90% completion of assembly for a single virion. Release of extracellular particles was observed at ∼1,500±700 s after the onset of assembly. The ability of the virus to recruit components of the cellular ESCRT machinery or to undergo proteolytic maturation, or the absence of Vpu did not significantly alter the assembly kinetics

Trehalose-6-phosphate-mediated toxicity determines essentiality of OtsB2 in Mycobacterium tuberculosis in vitro and in mice

Trehalose biosynthesis is considered an attractive target for the development of antimicrobials against fungal, helminthic and bacterial pathogens including Mycobacterium tuberculosis. The most common biosynthetic route involves trehalose-6-phosphate (T6P) synthase OtsA and T6P phosphatase OtsB that generate trehalose from ADP/UDP-glucose and glucose-6-phosphate. In order to assess the drug target potential of T6P phosphatase, we generated a conditional mutant of M. tuberculosis allowing the regulated gene silencing of the T6P phosphatase gene otsB2. We found that otsB2 is essential for growth of M. tuberculosis in vitro as well as for the acute infection phase in mice following aerosol infection. By contrast, otsB2 is not essential for the chronic infection phase in mice, highlighting the substantial remodelling of trehalose metabolism during infection by M. tuberculosis. Blocking OtsB2 resulted in the accumulation of its substrate T6P, which appears to be toxic, leading to the self-poisoning of cells. Accordingly, blocking T6P production in a ΔotsA mutant abrogated otsB2 essentiality. T6P accumulation elicited a global upregulation of more than 800 genes, which might result from an increase in RNA stability implied by the enhanced neutralization of toxins exhibiting ribonuclease activity. Surprisingly, overlap with the stress response caused by the accumulation of another toxic sugar phosphate molecule, maltose-1-phosphate, was minimal. A genome-wide screen for synthetic lethal interactions with otsA identified numerous genes, revealing additional potential drug targets synergistic with OtsB2 suitable for combination therapies that would minimize the emergence of resistance to OtsB2 inhibitors

Fig. 2 in Repatriation of knowledge about insects and types through the DORSA virtual museum (Digital Orthoptera Specimen Access)

Fig. 2: Species group names of Orthoptera worldwide (valid names and synonyms) and types specimens in German collections. The category holotype includes also syntypes, lectotypes and neotypes. [From Ingrisch et al. 2004a].Published as part of <i>Lampe, Karl Heinz, Riede, Klaus & Ingrisch, Sigfrid, 2005, Repatriation of knowledge about insects and types through the DORSA virtual museum (Digital Orthoptera Specimen Access), pp. 477-484 in Beiträge Zur Entomologie = Contributions to Entomology 55 (2)</i> on page 479, DOI: 10.21248/contrib.entomol.55.2.477-484, <a href="http://zenodo.org/record/10109455">http://zenodo.org/record/10109455</a&gt