»I am somewhat saddened that my esteemed colleague could misunderstand me in such a way«: The struggle for Karl Bühler’s theory of color constancy

Karl Bühlers Arbeiten auf dem Gebiet der Farbwahrnehmung spielen in der heutigen Rezeption seines Werkes nur eine untergeordnete Rolle. In diesem Beitrag werden Gründe für diese Situation erörtert. Anhand der lebhaften Kontroverse zwischen Bühler und Bühlers Mitarbeitern auf der einen und David Katz auf der anderen Seite kommen die Schwächen seiner Theorie der Farbenkonstanz und deren wichtige Impulse für die moderne Wahrnehmungspsychologie zur Sprache.Karl Bühler’s work in the field of color perception plays only a minor role in the reception of his work today. This paper discusses reasons for this situation. On the basis of the lively controversy between Bühler and Bühler’s collaborators on the one hand and David Katz on the other hand, the weaknesses of his theory of color constancy and its important impulses for modern perceptual psychology will be discussed

Identifying linear vector fields on 2D manifolds

Local linearity of vector fields is a property that is well researched and understood. Linear approximation can be used to simplify algorithms or for data reduction. Whereas the concept is easy to implement in 2D and 3D, it loses meaning on manifolds as linearity has either to be defined based on an embedding in a higher-dimensional Cartesian space or on a map. We present an adaptive atlas-based vector field decomposition to solve the problem on manifolds and present its application on synthetic and climate data

Investigation of the methylerythritol 4-phosphate pathway for microbial terpenoid production through metabolic control analysis

CITATION: Volke, D. C., et al. 2019. Investigation of the methylerythritol 4-phosphate pathway for microbial terpenoid production through metabolic control analysis. Microbial Cell Factories, 18:192, doi:10.1186/s12934-019-1235-5.The original publication is available at https://microbialcellfactories.biomedcentral.comBackground: Terpenoids are of high interest as chemical building blocks and pharmaceuticals. In microbes, terpenoids can be synthesized via the methylerythritol phosphate (MEP) or mevalonate (MVA) pathways. Although the MEP pathway has a higher theoretical yield, metabolic engineering has met with little success because the regulation of the pathway is poorly understood. Results: We applied metabolic control analysis to the MEP pathway in Escherichia coli expressing a heterologous isoprene synthase gene (ispS). The expression of ispS led to the accumulation of isopentenyl pyrophosphate (IPP)/ dimethylallyl pyrophosphate (DMAPP) and severely impaired bacterial growth, but the coexpression of ispS and isopentenyl diphosphate isomerase (idi) restored normal growth and wild-type IPP/DMAPP levels. Targeted proteomics and metabolomics analysis provided a quantitative description of the pathway, which was perturbed by randomizing the ribosome binding site in the gene encoding 1-deoxyxylulose 5-phosphate synthase (Dxs). Dxs has a flux control coefficient of 0.35 (i.e., a 1% increase in Dxs activity resulted in a 0.35% increase in pathway flux) in the isoprene-producing strain and therefore exerted significant control over the flux though the MEP pathway. At higher dxs expression levels, the intracellular concentration of 2-C-methyl-d-erythritol-2,4-cyclopyrophosphate (MEcPP) increased substantially in contrast to the other MEP pathway intermediates, which were linearly dependent on the abundance of Dxs. This indicates that 4-hydroxy-3-methylbut-2-en-1-yl diphosphate synthase (IspG), which consumes MEcPP, became saturated and therefore limited the flux towards isoprene. The higher intracellular concentrations of MEcPP led to the efflux of this intermediate into the growth medium. Discussion: These findings show the importance of Dxs, Idi and IspG and metabolite export for metabolic engineering of the MEP pathway and will facilitate further approaches for the microbial production of valuable isoprenoids.https://microbialcellfactories.biomedcentral.com/articles/10.1186/s12934-019-1235-5Publisher's versio