Extensive in vivo resilience of persistent Salmonella

Chronic infections caused by persistent pathogens represent an important health problem. Here, we establish a simple practical mouse Salmonella infection model for identifying bacterial maintenance functions that are essential for persistency. In this model, a substantial fraction of Salmonella survived even several days of treatment with a potent fluoroquinolone antibiotic indicating stringency of the model. Evaluation of twelve metabolic defects revealed dramatically different requirements for Salmonella during persistency as compared to acute infections. Disrupted synthesis of unsaturated/cyclopropane fatty acids was the only defect that resulted in rapid Salmonella clearance suggesting that this pathway might contain suitable targets for antimicrobial chemotherapy of chronic infection

A community effort towards a knowledge-base and mathematical model of the human pathogen Salmonella Typhimurium LT2

<p>Abstract</p> <p>Background</p> <p>Metabolic reconstructions (MRs) are common denominators in systems biology and represent biochemical, genetic, and genomic (BiGG) knowledge-bases for target organisms by capturing currently available information in a consistent, structured manner. <it>Salmonella enterica </it>subspecies I serovar Typhimurium is a human pathogen, causes various diseases and its increasing antibiotic resistance poses a public health problem.</p> <p>Results</p> <p>Here, we describe a community-driven effort, in which more than 20 experts in <it>S</it>. Typhimurium biology and systems biology collaborated to reconcile and expand the <it>S</it>. Typhimurium BiGG knowledge-base. The consensus MR was obtained starting from two independently developed MRs for <it>S</it>. Typhimurium. Key results of this reconstruction jamboree include i) development and implementation of a community-based workflow for MR annotation and reconciliation; ii) incorporation of thermodynamic information; and iii) use of the consensus MR to identify potential multi-target drug therapy approaches.</p> <p>Conclusion</p> <p>Taken together, with the growing number of parallel MRs a structured, community-driven approach will be necessary to maximize quality while increasing adoption of MRs in experimental design and interpretation.</p

A quantitative analysis of Salmonella Typhimurium metabolism during infection

In this thesis, Salmonella metabolism during infection was investigated. The goal was to gain a quantitative and comprehensive understanding of Salmonella in vivo nutrient supply, utilization and growth. To achieve this goal, we used a combined experimental / in silico approach. First, we generated a reconstruction of Salmonella metabolism ([1], see 2.1). This reconstruction was then combined with in vivo data from experimental mutant phenotypes to build a comprehensive quantitative in vivo model of Salmonella metabolism during infection (unpublished data, see 2.2). The data indicated that Salmonella resided in a quantitatively nutrient poor environment, which limited Salmonella in vivo growth. On the other hand, the in vivo niche of Salmonella was qualitatively rich with at least 45 different metabolites available to Salmonella. We then used the in vivo model of infection to analyze reasons for the preponderance of Salmonella genes with undetectable virulence phenotype (unpublished data, see 2.3). Our data indicated that host supply with diverse nutrients resulted in large-scale inactivity of numerous Salmonella metabolic pathways. This together with extensive metabolic redundancy was the main cause of the massive Salmonella gene dispensability during infection. To verify this hypothesis experimentally, an unbiased method for large scale mutagenesis was developed (unpublished data, see 2.4). Results from 20 Salmonella mutator lines indicate that Salmonella can tolerate at least some 2700 to 3900 mutations, emphasizing again that a vast majority of Salmonella genes are dispensable in a defined environment

Localization and location-based application for museums

In dieser Arbeit wird ein Museumsführer für Android entwickelt, der Informationen zu Exponaten anzeigt. Mit Hilfe mehrerer WLAN Access Points im Museum ermittelt der Museumsführer die Exponate in der Nähe des Besuchers und vereinfacht damit deren Suche. Zusätzlich ist an jedem Museumsstück eine Station auf Gadgeteer-Basis angebracht, mit der die Besucher interagieren können um Informationen zum Ausstellungsstück zu erhalten. Es werden drei unterschiedliche Stationen entwickelt: Zwei werden mit der Hand in Kombination mit einem RFID-Armband bedient und eine kommuniziert direkt mit dem Museumsführer über NFC. Die Museumsinhalte liegen auf einem Server und können von den Kuratoren über ein Web-Frontend verwaltet werden. Bei der Installation enthält die App keine Museumsdaten und kann die Inhalte von allen Museen, die dieses System verwenden, laden. In einer Laborstudie wurde das System von den Probanden positiv bewertet. Für den produktiven Einsatz im Museum sind aber noch Verbesserungen nötig.In this work, a museum guide for Android is developed, which displays information of the exhibits. With the help of several WLAN Access Points the museum guide determines the exhibits in the vicinity of the visitor and thus simplifies the search for them. In addition, each exhibit is augmented with a station based on Gadgeteer hardware. The visitors can interact with them in order to obtain information about the corresponding exhibit. Three different stations were developed: two are used by hand in combination with a RFID bracelet and one station communicates directly with the android museum guide with NFC. The museum content is stored on a server and can be managed by the curators through a web frontend. On installation the android application has no museum content included. Content can be loaded in every museum that uses this system. In a laboratory study the system was evaluated positively. But improvements are still needed for productive use in a museum

Clearance of <i>Salmonella purA ssaGH fabB</i> from infected mice.

<p>A) Colonization kinetics in spleen (open circles) and liver (filled circles). Similar results were obtained in three independent experiments. Statistical significance of clearance at day 7 compared to day 1 were determined by t-test of log-transformed data (***, <i>P</i><0.001; **, <i>P</i><0.01; *, <i>P</i><0.05; n.s., not significant). B) Heterogeneity of colony size on agar plates. Similar data were obtained for two independent in vitro cultures and five independent ex vivo cultures.</p

Colonization kinetics of <i>Salmonella enterica serovar Typhimurium purA ssaGH</i> in systemically infected BALB/c mice.

<p>Data are shown for spleen (<b>A</b>) and liver (<b>B</b>) of individual untreated mice (open circles), and mice that were treated from day two post infection with enrofloxacin (filled circles). Statistical significance of clearance at day 6 compared to day 4 were determined by t-test of log-transformed data (**, <i>P</i><0.01; n.s., not significant).</p

Competitive indices (CI) of various <i>Salmonella</i> mutants vs. the parental <i>Salmonella purA ssaGH</i> strain in infected spleen (open circles) and liver (filled circles).

<p>Data are shown for individual mice at day seven post infection. A competitive index of 1 indicates equal colonization capabilities of mutant and parental strains. Statistical significance was determined by t-test of log-transformed data. Spleen colonization of mutants <i>ppk, recA, trxA, ubiC</i>, and <i>fadD fadK</i> was significantly lower compared to the parental strain (<i>P</i><0.05). Liver colonization of mutants <i>ppk, recA,</i> and <i>fadD fadK</i> was significantly lower compared to the parental strain (<i>P</i><0.05).</p

Colonization kinetics of four compromised mutants in spleen (open circles) and liver (filled circles).

<p>Small residual colonization levels after seven days of infection suggested that all shown genes contributed to <i>Salmonella</i> survival but were not absolutely essential. Statistical significance of clearance at day 7 compared to day 1 in spleen was determined by t-test of log-transformed data (***, <i>P</i><0.001).</p

Parallel Exploitation of Diverse Host Nutrients Enhances Salmonella Virulence

Pathogen access to host nutrients in infected tissues is fundamental for pathogen growth and virulence, disease progression, and infection control. However, our understanding of this crucial process is still rather limited because of experimental and conceptual challenges. Here, we used proteomics, microbial genetics, competitive infections, and computational approaches to obtain a comprehensive overview of Salmonella nutrition and growth in a mouse typhoid fever model. The data revealed that Salmonella accessed an unexpectedly diverse set of at least 31 different host nutrients in infected tissues but the individual nutrients were available in only scarce amounts. Salmonella adapted to this situation by expressing versatile catabolic pathways to simultaneously exploit multiple host nutrients. A genome-scale computational model of Salmonella in vivo metabolism based on these data was fully consistent with independent large-scale experimental data on Salmonella enzyme quantities, and correctly predicted 92% of 738 reported experimental mutant virulence phenotypes, suggesting that our analysis provided a comprehensive overview of host nutrient supply, Salmonella metabolism, and Salmonella growth during infection. Comparison of metabolic networks of other pathogens suggested that complex host/pathogen nutritional interfaces are a common feature underlying many infectious diseases