Daniel Kuehner

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HPLC bioautography of the directed biosynthesis of Zalerion arboricola led to the discovery of pneumocandin B0 (L-688,786), a new antifungal and anti-Pneumocystis carinii lipopeptide. Isolation techniques were developed to separate this component from pneumocandin A0 (L-671,329) in fermentations of a mutant of Zalerion arboricola. A number of related(More)
Bacterial conjugation normally involves the unidirectional transfer of DNA from donor to recipient. Occasionally, conjugation results in the transfer of DNA from recipient to donor, a phenomenon known as retrotransfer. Two distinct models have been generally considered for the mechanism of retrotransfer. In the two-way conduction model, no transfer of the(More)
Peptidoglycans (PGNs) are immunogenic bacterial surface patterns that trigger immune activation in metazoans and plants. It is generally unknown how complex bacterial structures such as PGNs are perceived by plant pattern recognition receptors (PRRs) and whether host hydrolytic activities facilitate decomposition of bacterial matrices and generation of(More)
Cell wall thickening is a common feature among daptomycin-resistant Staphylococcus aureus strains. However, the mechanism(s) leading to this phenotype is unknown. We examined a number of cell wall synthesis pathway parameters in an isogenic strain set of S. aureus bloodstream isolates obtained from a patient with recalcitrant endocarditis who failed(More)
Multiple mechanisms have been correlated with daptomycin-resistance (DAP-R) in Staphylococcus aureus. However, one common phenotype observed in many DAP-R S. Aureus strains is a thickened cell wall (CW). The first evidence for an impact of CW-linked glycopolymers on this phenotype was recently demonstrated in a single, well-characterized DAP-R(More)
Using Radix imperatoriae (the root of masterwort) as an example, we describe an efficient approach for the isolation, identification and evaluation of bioactive plant components on an analytical scale. The extraction of Radix imperatoriae with ethyl acetate was enhanced by the application of ultrasound oscillations. This rhizome extract was applied to three(More)
Intimin and Invasin are prototypical inverse (Type Ve) autotransporters and important virulence factors of enteropathogenic Escherichia coli and Yersinia spp. respectively. In addition to a C-terminal extracellular domain and a β-barrel transmembrane domain, both proteins also contain a short N-terminal periplasmic domain that, in Intimin, includes a lysin(More)
Peptidoglycan (PGN) is ubiquitous in nearly all bacterial species. The PGN sacculus protects the cells against their own internal turgor making PGN one of the most important targets for antibacterial treatment. Within the last sixty years PGN composition has been intensively studied by various methods. The breakthrough was the application of HPLC technology(More)
Mutations in the nucleotide-binding oligomerization domain-containing protein 2 (NOD2) play an important role in the pathogenesis of Crohn's disease. NOD2 is an intracellular pattern recognition receptor (PRR) that senses bacterial peptidoglycan (PGN) structures, e.g., muramyl dipeptide (MDP). Here we focused on the effect of more-cross-linked, polymeric(More)
Within the last 60 years peptidoglycan (PGN) composition of bacteria has been intensively studied by various methods. However, preparation of pure PGN relied on a very time-consuming method. We established a purification protocol which can be completely performed in plastic reaction tubes or even microtiter plates within 24 hours. The muropeptides can be(More)