TY  - JOUR
A1  - Mietrach, Nicole
A1  - Schlosser, Andreas
A1  - Geibel, Sebastian
T1  - An extracellular domain of the EsaA membrane component of the type VIIb secretion system: expression, purification and crystallization
JF  - Acta Crystallographica Section F
N2  - The membrane protein EsaA is a conserved component of the type VIIb secretion system. Limited proteolysis of purified EsaA from Staphylococcus aureus USA300 identified a stable 48 kDa fragment, which was mapped by fingerprint mass spectrometry to an uncharacterized extracellular segment of EsaA. Analysis by circular dichroism spectroscopy showed that this fragment folds into a single stable domain made of mostly α‐helices with a melting point of 34.5°C. Size‐exclusion chromatography combined with multi‐angle light scattering indicated the formation of a dimer of the purified extracellular domain. Octahedral crystals were grown in 0.2 M ammonium citrate tribasic pH 7.0, 16% PEG 3350 using the hanging‐drop vapor‐diffusion method. Diffraction data were analyzed to 4.0 Å resolution, showing that the crystals belonged to the enantiomorphic tetragonal space groups P41212 or P43212, with unit‐cell parameters a = 197.5, b = 197.5, c = 368.3 Å, α = β = γ = 90°.
KW  - ESAT‐6‐like secretion system
KW  - ESS
KW  - type VII secretion system
KW  - EsaA
KW  - extracellular domain
KW  - Staphylococcus aureus USA300
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-213681
VL  - 75
IS  - 12
ER  - 
TY  - JOUR
A1  - Poethke, Hans J.
A1  - Hovestadt, Thomas
T1  - Evolution of density-and patch-size-dependent dispersal rates
N2  - Based on a marginal value approach, we derive a nonlinear expression for evolutionarily stable (ES) dispersal rates in a metapopulation with global dispersal. For the general case of density-dependent population growth, our analysis shows that individual dispersal rates should decrease with patch capacity and-beyond a certain threshold-increase with population density. We performed a number of spatially explicit, individual-based simulation experiments to test these predictions and to explore further the relevance of variation in the rate of population increase, density dependence, environmental fluctuations and dispersal mortality on the evolution of dispersal rates. They confirm the predictions of our analytical approach. In addition, they show that dispersal rates in metapopulations mostly depend on dispersal mortality and inter-patch variation in population density. The latter is dominantly driven by environmental fluctuations and the rate of population increase. These conclusions are not altered by the introduction of neighbourhood dispersal. With patch capacities in the order of 100 individuals, kin competition seems to be of negligible importance for ES dispersal rates except when overall dispersal rates are low.
KW  - Metapopulation
KW  - Dichte
KW  - Verteilung
KW  - density-dependent dispersal
KW  - metapopulation
KW  - patch size
KW  - ESS
KW  - dispersal rate
KW  - individual based model (IBM)
Y1  - 2002
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-49659
ER  - 
TY  - JOUR
A1  - Poethke, Hans-Joachim
A1  - Hovestadt, Thomas
A1  - Mitesser, Oliver
T1  - Local extinction and the evolution of dispersal rates: Causes and correlations
N2  - We present the results of individual-based simulation experiments on the evolution of dispersal rates of organisms living in metapopulations. We find conflicting results regarding the relationship between local extinction rate and evolutionarily stable (ES) dispersal rate depending on which principal mechanism causes extinction: if extinction is caused by environmental catastrophes eradicating local populations, we observe a positive correlation between extinction and ES dispersal rate; if extinction is a consequence of stochastic local dynamics and environmental fluctuations, the correlation becomes ambiguous; and in cases where extinction is caused by dispersal mortality, a negative correlation between local extinction rate and ES dispersal rate emerges. We conclude that extinction rate, which both affects and is affected by dispersal rates, is not an ideal predictor for optimal dispersal rates.
KW  - Ausbreitung
KW  - Evolution
KW  - Computersimulation
KW  - Metapopulation
KW  - dispersal
KW  - evolution
KW  - ESS
KW  - metapopulation
KW  - extinction
KW  - individual-based model
Y1  - 2003
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-47718
ER  -