Biology subjects

Wennekes, T.

Publications and source records attributed to Wennekes, T..

4 recordsLinked to original sources

bioRxiv2026

Development of difluoro-Kdn mechanism-based probes to label and visualize Kdnases in Aspergillus fumigatus

Kdnases have been reported in a variety of organisms, including marine species such as trout and oysters, the opportunistic Gram-negative bacterium Sphingobacterium multivorum, and several fungal species of the genus Aspergillus, including Aspergillus terreus and Aspergillus fumigatus.. In particular, the Kdnase from the opportunistic airborne pathogen Aspergillus fumigatus (AfKdnase) plays an important role in fungal cell wall integrity and virulence, although the underlying mechanisms remain unclear. To better understand this class of enzymes, selective and sensitive tools are required for discovery, detection and visualization of active Kdnases in complex biological samples. In this work, we report the development of difluoro-Kdn mechanism-based probes functionalized with azide and biotin tags for labeling and detection of Kdnases. We show that the probes exhibit selectivity for Kdnase over the neuraminidases tested and efficiently label recombinantly expressed AfKdnase at micromolar concentrations. In addition, using the azide-bearing probe and click chemistry, we successfully visualized native Kdnases in A. fumigatus mycelia, demonstrating their utility for studying these enzymes in crude biological samples and highlighting their potential for discovering Kdnases in other organisms including fungal and bacterial species.

biochemistry↗

bioRxiv2024

Glycoengineering with neuraminic acid analogs to label lipooligosaccharides and detect native sialyltransferase activity in Gram-negative bacteria

Lipooligosaccharides (LOS) are the most abundant cell surface glycoconjugates on the outer membrane of Gram-negative bacteria. They play important roles in host-microbe interactions. Certain Gram-negative pathogenic bacteria cap their LOS with the sialic acid, N-acetylneuraminic acid (Neu5Ac), to mimic host glycans that among others protects these bacteria from recognition by the hosts immune system. This process of molecular mimicry is not fully understood and remains under investigated. To explore the functional role of sialic acid-capped lipooligosaccharides (LOS) at the molecular level, it is important to have tools readily available for the detection and manipulation of both Neu5Ac on glycoconjugates and the involved sialyltransferases, preferably in live bacteria. We and others have shown that the native sialyltransferases of some Gram-negative bacteria can incorporate extracellular unnatural sialic acid nucleotides onto their LOS. We here report on the expanded use of native bacterial sialyltransferases to incorporate neuraminic acids analogs with a reporter group into the LOS of a variety of Gram-negative bacteria. We show that this approach offers a quick strategy to screen bacteria for the expression of functional sialyltransferases and the ability to use exogenous CMP-Neu5Ac to decorate their glycoconjugates. For selected bacteria we also show this strategy complements two other glycoengineering techniques, Metabolic Oligosaccharide Engineering (MOE) and Selective Exo-Enzymatic Labelling (SEEL), and that together they provide tools to modify, label, detect and visualize sialylation of bacterial LOS.

microbiology↗

bioRxiv2022

Structure-activity relationship of 2,4-D correlates auxin activity with the induction of somatic embryogenesis in Arabidopsis thaliana

2,4-dichlorophenoxyacetic acid (2,4-D) is a synthetic analogue of the plant hormone auxin that is commonly used in many in vitro plant regeneration systems, such as somatic embryogenesis (SE). Its effectiveness in inducing SE, compared to the natural auxin indole-3-acetic acid (IAA), has been attributed to the stress triggered by this compound rather than its auxin activity. However, this hypothesis has never been thoroughly tested. Here we used a library of 40 2,4-D analogues to test the structure-activity relationship with respect to the capacity to induce SE and auxin activity in Arabidopsis thaliana. Four analogues induced SE as effectively as 2,4-D and 13 analogues induced SE but were less effective. Based on root growth inhibition and auxin response reporter expression, the 2,4-D analogues were classified into different groups, ranging from very active auxins to not active. A halogen at the 4-position of the aromatic ring was important for auxin activity, whereas a halogen at the 3-position resulted in reduced activity. Moreover, a small substitution at the carboxylate chain was tolerated, as was extending the carboxylate chain with two but not with one carbon. In the process, we also identified two 2,4-D analogues as efficient inducers of adventitious root formation and several possible anti-auxins. The auxin activity of the 2,4-D analogues was consistent with their simulated TIR1-Aux/IAA coreceptor binding characteristics. A strong correlation was observed between SE induction efficiency and auxin activity, indicating that the stress-related effects triggered by 2,4-D that are considered important for SE induction are down-stream of auxin signaling.

plant biology↗

bioRxiv2020

Outer membrane permeabilization by the membrane attack complex sensitizes Gram-negative bacteria to antimicrobial proteins in serum and phagocytes

Infections with Gram-negative bacteria form an increasing risk for human health, which is mainly due to the increase in antibiotic resistance. The cell envelope of Gram-negative bacteria consists of an inner membrane, a peptidoglycan layer and an outer membrane, which forms an impermeable barrier to many antibiotics and antimicrobial proteins. The complement system is an important factor of the human immune system that can efficiently kill Gram-negative bacteria via the formation of large pores in the bacterial outer membrane, called Membrane Attack Complexes (MACs). To better understand how these MAC pores damage the complex cell envelope of Gram-negative bacteria, we recently developed a fluorescent reporter system to study membrane damage in E. coli. Here, we used a similar experimental setup in combination with flow cytometry, confocal microscopy and conventional plating assays to elucidate how different components of the immune system act synergistically to effectively clear invading bacteria. We demonstrate how MAC-dependent outer membrane damage enhances the susceptibility of E. coli to further degradation of the cell envelope by lysozyme, leading to drastic changes in the morphology of these bacteria. Furthermore, we elucidate that the MAC enhances the susceptibility of E. coli to phospholipases, and to degradation and killing inside human neutrophils. Altogether, this study provides a detailed overview on how different players of the human immune system work closely together to degrade the complex cell envelope of Gram-negative bacteria. This knowledge may facilitate the development of new antimicrobials that could stimulate, or work synergistically with the immune system.

immunology↗