Fatty acid synthesis in Escherichia coli and its applications towards the production of fatty acid based biofuels

The idea of renewable and regenerative resources has inspired research for more than a hundred years. Ideally, the only spent energy will replenish itself, like plant material, sunlight, thermal energy or wind. Biodiesel or ethanol are examples, since their production relies mainly on plant material. However, it has become apparent that crop derived biofuels will not be sufficient to satisfy future energy demands. Thus, especially in the last decade a lot of research has focused on the production of next generation biofuels. A major subject of these investigations has been the microbial fatty acid biosynthesis with the aim to produce fatty acids or derivatives for substitution of diesel. As an industrially important organism and with the best studied microbial fatty acid biosynthesis, Escherichia coli has been chosen as producer in many of these studies and several reviews have been published in the fields of E. coli fatty acid biosynthesis or biofuels. However, most reviews discuss only one of these topics in detail, despite the fact, that a profound understanding of the involved enzymes and their regulation is necessary for efficient genetic engineering of the entire pathway. The first part of this review aims at summarizing the knowledge about fatty acid biosynthesis of E. coli and its regulation, and it provides the connection towards the production of fatty acids and related biofuels. The second part gives an overview about the achievements by genetic engineering of the fatty acid biosynthesis towards the production of next generation biofuels. Finally, the actual importance and potential of fatty acid-based biofuels will be discussed

Multifractality of wavefunctions at the quantum Hall transition revisited

We investigate numerically the statistics of wavefunction amplitudes $\psi({\bf r})$ at the integer quantum Hall transition. It is demonstrated that in the limit of a large system size the distribution function of $|\psi|^2$ is log-normal, so that the multifractal spectrum $f(\alpha)$ is exactly parabolic. Our findings lend strong support to a recent conjecture for a critical theory of the quantum Hall transition.Comment: 4 pages Late

Impact of secondary hard substrate on the distribution and abundance of Aurelia aurita in the western Baltic Sea

Highlights: • Impacts of wind farms on the occurrence of the moon jelly Aureliaaurita. • Artificial hard substrate has the potential to increase the abundance of A.aurita. • In the given example the abundance of A. aurita increases about 20%. • Distribution patterns indicate cross-border impacts on various sectors. This study assessed the impact of secondary hard substrate, as being introduced into marine ecosystems by the establishment of wind farm pillars, on the occurrence and distribution of the moon jelly Aurelia aurita in the southwestern Baltic Sea. A two-year data sampling was conducted with removable settlement plates to assess the distribution and population development of the scyphozoan polyps. The data collected from these samples were used to set up a model with Lagrangian particle technique. The results confirm that anthropogenic created hard substrate (e.g. offshore wind farms) has the potential to increase the abundance of the A. aurita population. The distribution of wind farm borne jellyfish along Danish, German and Polish coasts indicates conflicts with further sectors, mainly energy and tourism

Optimization of macroelement concentrations, pH and osmolarity for triacylglycerol accumulation in Rhodococcus opacus strain PD630

The refinement of biodiesel or renewable diesel from bacterial lipids has a great potential to make a contribution for energy production in the future. This study provides new data concerning suitable nutrient concentrations for cultivation of the Gram-positive Rhodococcus opacus PD630, which is able to accumulate large amounts of lipids during nitrogen limitation. Enhanced concentrations of magnesium have been shown to increase the final optical density and the lipid content of the cells. Elevated phosphate concentrations slowed down the onset of the accumulation phase, without a clear effect on the final optical density and the cell’s lipid content. A robust growth of R. opacus was possible in the presence of ammonium concentrations of up to 1.4 g l-1 and sucrose concentrations of up to 240 g l-1, with an optimum regarding growth and lipid storage observed in the range of 0.2 to 0.4 g l-1 ammonium and 20 to 40 g l-1 sucrose, respectively. Moreover, R. opacus showed tolerance to high salt concentrations

Engineering fatty acid synthases for directed polyketide production.

In this study, we engineered fatty acid synthases (FAS) for the biosynthesis of short-chain fatty acids and polyketides, guided by a combined in vitro and in silico approach. Along with exploring the synthetic capability of FAS, we aim to build a foundation for efficient protein engineering, with the specific goal of harnessing evolutionarily related megadalton-scale polyketide synthases (PKS) for the tailored production of bioactive natural compounds

Residential Segregation of the Foreign Population in Germany. An Analysis Based on German Microcensus Data

Im vorliegenden Beitrag wird ethnische Segregation in Westdeutschland auf kleinräumiger Ebene mit Daten des Mikrozensus gemessen. Für die größten Migrantengruppen der ehemaligen Anwerbeländer werden die zeitlichen Entwicklungen nachgezeichnet. Gemessen am mittleren Anteil der ausländischen Bevölkerung der nächsten Nachbarschaften hat die räumliche Segregation Zugewanderter von 1976 bis 1982 zugenommen, während in den Jahren von 1996 bis 2004 ein abnehmender Trend zu beobachten ist. Dabei zeigen sich kaum Unterschiede zwischen den Migrantengenerationen. Erst unter Kontrolle weiterer Einfluss¬faktoren variieren die erste und die zweite Generation. Zur Erklärung, ob eine Person in einer ethnisch hoch segregierten Nachbarschaft wohnt, tragen u.a. Bildungsniveau und Einkommens¬situation als Indikatoren der sozialstrukturellen Integration bei. Sowohl für Migranten als auch für Deutsche gibt es einen Zusammenhang zwischen geringer Bildung sowie relativer Einkommensarmut und Wohngebieten mit einer hohen Ausländerquote. Allerdings bleiben auch unter Berücksichtigung dieser Faktoren deutliche Unterschiede zwischen Deutschen und Migranten sowie zwischen den ausländischen Nationalitäten bestehen.The present paper examines ethnic segregation on a very small scale using Microcensus data. The development of ethnic segregation is traced for the largest foreign population groups stemming from those countries in which foreign workers were once recruited. Residential segregation is measured by the average proportion of foreign-origin population in the small census districts. Whereas segregation increased between 1976 and 1982, a decreasing trend has been observed since 1996. There are almost no differences between the generations. The first and second generations only vary if further variables are taken into account. Indicators of socio-economic integration such as the level of education and the economic situation have explanatory power with regards to living in an highly segregated area. There is a correlation between a low educational level as well as relative poverty and neighborhoods with high proportions of foreign-origin population. Nevertheless, even if various factors are considered, noticeable differences remain both between Germans and migrants and within the foreign nationalities

Projektvorstellung: Wasserhaushalt einer geschichteten mineralischen Deponieabdichtung

Die langfristige sichere Abdichtung von Mülldeponiekörpern ist bei der Verwendung von Geotextilien sehr teuer, der Einsatz von mineralischen Tondichtungen erfordert eine sehr präzise Ausführung und darüber hinaus auch eine genaue Steuerung der internen Wasserhaushaltssituation, um Rissbildung zu vermeiden. Daher soll in dem Projekt ein in der Theorie bereits nachvollziehbares Abdichtungsverfahren (geschichtetes mineralisches Abdeckungssystem) auf in situ Bedingungen übertragen und unter Realbedingungen dann auch auf ihre Funktionsfähigkeit überprüft werden. Hierzu werden auf der Mülldeponie Rastorf, die eine temporäre Deponieabdeckung hat, sowohl in situ Messungen durchgeführt (Tensiometer- und Wassergehaltsmessungen) als auch Laborproben zur Erfassung der räumlichen hydraulischen Leitfähigkeit am Hang (Tensorfunktion) entnommen. Ziel ist die Validierung einer theoretisch sehr gut nachgewiesenen Dichtungswirkung unter Freilandbedingungen, um ein wirtschaftliches und langfristig sicheres Deponieabdichtungssystem zu erstellen

Liouvillian Approach to the Integer Quantum Hall Effect Transition

We present a novel approach to the localization-delocalization transition in the integer quantum Hall effect. The Hamiltonian projected onto the lowest Landau level can be written in terms of the projected density operators alone. This and the closed set of commutation relations between the projected densities leads to simple equations for the time evolution of the density operators. These equations can be used to map the problem of calculating the disorder averaged and energetically unconstrained density-density correlation function to the problem of calculating the one-particle density of states of a dynamical system with a novel action. At the self-consistent mean-field level, this approach yields normal diffusion and a finite longitudinal conductivity. While we have not been able to go beyond the saddle point approximation analytically, we show numerically that the critical localization exponent can be extracted from the energetically integrated correlation function yielding $\nu=2.33 \pm 0.05$ in excellent agreement with previous finite-size scaling studies.Comment: 9 pages, submitted to PR

Metal-insulator transitions in anisotropic 2d systems

Several phenomena related to the critical behaviour of non-interacting electrons in a disordered 2d tight-binding system with a magnetic field are studied. Localization lengths, critical exponents and density of states are computed using transfer matrix techniques. Scaling functions of isotropic systems are recovered once the dimension of the system in each direction is chosen proportional to the localization length. It is also found that the critical point is independent of the propagation direction, and that the critical exponents for the localization length for both propagating directions are equal to that of the isotropic system (approximately 7/3). We also calculate the critical value of the scaling function for both the isotropic and the anisotropic system. It is found that the isotropic value equals the geometric mean of the two anisotropic values. Detailed numerical studies of the density of states for the isotropic system reveals that for an appreciable amount of disorder the critical energy is off the band center.Comment: 6 pages RevTeX, 6 figures included, submitted to Physical Review

A Real-Time Thermal Sensor System for Quantifying the Inhibitory Effect of Antimicrobial Peptides on Bacterial Adhesion and Biofilm Formation

The increasing rate of antimicrobial resistance (AMR) in pathogenic bacteria is a global threat to human and veterinary medicine. Beyond antibiotics, antimicrobial peptides (AMPs) might be an alternative to inhibit the growth of bacteria, including AMR pathogens, on different surfaces. Biofilm formation, which starts out as bacterial adhesion, poses additional challenges for antibiotics targeting bacterial cells. The objective of this study was to establish a real-time method for the monitoring of the inhibition of (a) bacterial adhesion to a defined substrate and (b) biofilm formation by AMPs using an innovative thermal sensor. We provide evidence that the thermal sensor enables continuous monitoring of the effect of two potent AMPs, protamine and OH-CATH-30, on surface colonization of bovine mastitis-associated Escherichia (E.) coli and Staphylococcus (S.) aureus. The bacteria were grown under static conditions on the surface of the sensor membrane, on which temperature oscillations generated by a heater structure were detected by an amorphous germanium thermistor. Bacterial adhesion, which was confirmed by white light interferometry, caused a detectable amplitude change and phase shift. To our knowledge, the thermal measurement system has never been used to assess the effect of AMPs on bacterial adhesion in real time before. The system could be used to screen and evaluate bacterial adhesion inhibition of both known and novel AMPs