Simon Sieber

University of Zurich | UZH · Chemistry

Amine-containing natural products are an important class of therapeutic compounds. Herein, we report a chemoselective approach to catch and enrich amine-containing natural products, and release them as underivatized compounds. The...

Isonitrile‐containing natural products have garnered attention for their manifold bioactivities but are difficult to detect and isolate due to the chemical lability of the isonitrile functional group. Here, we used the isonitrile‐chlorooxime ligation (INC) in a reactivity‐based screening (RBS) protocol for the detection and isolation of alkaloid an...

Chirality plays a critical role in the biochemistry of life and often only one enantiomeric series is observed (homochirality). Only a few natural products have been obtained as racemates, e.g. the signalling molecule valdiazen produced by Burkholderia cenocepacia H111. In this study, we investigated the ham biosynthetic gene cluster and discovered...

Over the last two decades, proliferations of benthic cyanobacteria producing derivatives of anatoxin-a have been reported in rivers worldwide. Here, we follow up on such a toxigenic event happening in the Areuse river in Switzerland and investigate the diversity and genomics of major bloom-forming riverine benthic cyanobacteria. We show, using 16S...

Specialized or secondary metabolites are small molecules of biological origin, often showing potent biological activities with applications in agriculture, engineering and medicine. Usually, the biosynthesis of these natural products is governed by sets of co-regulated and physically clustered genes known as biosynthetic gene clusters (BGCs). To sh...

CyanoMetDB is a comprehensive database of secondary metabolites from cyanobacteria manually curated from primary references described in Jones et al (2021), DOI: 10.1016/j.watres.2021.117017 (preprint DOI: 10.1101/2020.04.16.038703). This upload contains the 2024 release. Please cite Jones et al (2021) DOI: 10.1016/j.watres.2021.117017 and this rec...

Mercury is a highly toxic trace metal that can accumulate in aquatic ecosystems and when resent at high concentrations can pose risks to both aquatic life and humans consuming contaminated fish. This research explores the use of the metalloregulatory protein MerR, known for its high affinity and selectivity toward mercury, in a novel application. T...

The bacterial plant pathogen Pseudomonas syringae causes significant damage to economically important crops worldwide. These bacteria coordinate their behavior and virulence through specific signaling compounds, such as the diazeniumdiolate leudiazen. Conventional antibacterial treatments enable the development of resistant strains. A more attracti...

Chirality features a critical role in the biochemistry of life and often only one enantiomeric series is observed (homochirality). Only few natural products have been obtained as racemates, e.g. the quorum-sensing signal valdiazen produced by Burkholderia cenocepacia H111. In this study, we investigated its biosynthetic gene cluster and discovered...

Inefficient wound healing poses a global health challenge with a lack of efficient treatments. Wound healing issues often correlate with low endogenous nitric oxide (NO) levels. While exogenous delivery with NO‐releasing compounds represents a promising therapeutic strategy, controlling the release of the highly reactive NO remains challenging. Pho...

In the last ten years, blooms of benthic cyanobacteria producing derivatives of the potent neurotoxin anatoxin-a have been repeatedly reported in rivers of temperate regions all over the world. For three series of events, in New Zealand, the USA, and Canada, a cohesive cluster of Microcoleus strains was found to be responsible for the toxin synthes...

Allylic cyclitols were investigated as covalent inhibitors of glycoside hydrolases by chemical, enzymatic, proteomic, and computational methods. This approach was inspired by the C7 cyclitol natural product streptol glucoside, which features a potential carbohydrate leaving group in the 4-position (carbohydrate numbering). To test this hypothesis,...

The symbioses between plants of the Rubiaceae and Primulaceae families with Burkholderia bacteria represent unique and intimate plant-bacterial relationships. Many of these interactions have been identified through PCR-dependent typing methods, but there is little information available about their functional and ecological roles. We assembled seven...

The symbioses between plants of the Rubiaceae and Primulaceae families with Burkholderia bacteria represent unique and intimate plant-bacterial relationships. Many of these interactions have been identified through PCR-dependent typing methods, but there is little information available about their functional and ecological roles. We assembled seven...

Antimicrobial resistance in pathogenic bacteria is considered a major public health issue necessitating the discovery of alternative antimicrobial compounds. In this regard, targeted genome mining in bacteria occupying under-explored ecological niches has the potential to reveal such compounds, including bacteriocins. In this study, we determined t...

Cell-surface display systems are biotechnological techniques used to express heterologous proteins on the cell surface. Their application depends directly on the cell system used, as well as on the anchoring point for the surface displayed protein. To meet most application demands an inexpensive, safe, and scalable production platform, that reduces...

After a century of investigations, the function of the obligate betaproteobacterial endosymbionts accommodated in leaf nodules of tropical Rubiaceae remained enigmatic. We report that the α-d-glucose analogue (+)-streptol, systemically supplied by mature Ca.Burkholderia kirkii nodules to their Psychotria hosts, exhibits potent and selective root gr...

Pseudomonas syringae is an important plant pathogen of many valuable crops worldwide, with more than 60 identified pathovars. The phytotoxins produced by these organisms were related to the severity of the damage caused to the plant. An emerging strategy to treat bacterial infections relies on interference with their signaling systems. In this stud...

Cell-surface display systems are biotechnological techniques used to expose heterologous proteins on the cell surface. Their application depends directly on the cell system used for the development, as well as anchoring point surface displayed protein. To meet most application demands an inexpensive, safe, and scalable production platform, that red...

The open innovation hub Digital Health and Patient Safety Platform (DHPSP) was recently established with the purpose to invigorate collaborative scientific research and the development of new digital products and personalized solutions aiming to improve human health and patient safety. In this study, we evaluated the effectiveness of a Twitter-base...

Bacterial and viral infections pose a direct threat to human health due to the increase of drug-resistant and novel pathogenic strains. Natural products represent a prolific source of bioactive metabolites, which have been exploited for their therapeutic effects. In particular, cyanobacteria were identified as important producers of secondary metab...

New strategies to efficiently treat bacterial infections are crucial to circumvent the increase of resistant strains and to mitigate side effects during treatment. Skin and soft tissue infections represent one of the areas suffering the most from these resistant strains. We developed a new drug delivery system composed of the green algae, Chlamydom...

Pseudomonas syringae is an important pathogen of many agriculturally valuable crops. Among the various pathovars described P. syringae pv. syringae (Pss) has a particularly wide host range, infecting primarily woody and herbaceous host plants. The ability of Pss to cause bacterial apical necrosis of mango trees is dependent on the production of the...

Pseudomonas syringae is an important pathogen of many agriculturally valuable crops. Among the various pathovars described P. syringae pv. syringae (Pss) has a particularly wide host range, infecting primarily woody and herbaceous host plants. The ability of Pss to cause bacterial apical necrosis of mango trees is dependent on the production of the...

div> Pseudomonas syringae is an important pathogen of many agriculturally valuable crops. Among the various pathovars described P. syringae pv. syringae (Pss) has a particularly wide host range, infecting primarily woody and herbaceous host plants. The ability of Pss to cause bacterial apical necrosis of mango trees is dependent on the production...

The C7N-aminocyclitol kirkamide was recently isolated from the plant obligate symbiont Candidatus Burkholderia kirkii and was hypothesized to be beneficial to the plant host due to its cytotoxic activity against insects and arthropods. To study its mechanism of action and inspired by its structural similarity with N-acetylglucosamine (GlcNAc) and o...

We designed and engineered a dye production cassette encoding a heterologous pathway, including human tyrosine hydroxylase and Amanita muscaria 4,5-DOPA dioxygenase, for the biosynthesis of the betaxanthin family of plant and fungal pigments in mammalian cells. The system does not impair cell viability, and can be used as a non-protein reporter sys...

Only a few natural products incorporating a diazeniumdiolate moiety have been isolated, and these compounds usually display a broad range of biological activities. Only recently has the first diazeniumdiolate natural product biosynthetic gene cluster been identified in Burkholderia cenocepacia H111, which produces the fungicide (−)‐fragin and the s...

We report the synthesis and first characterisation of the novel chemical probe 3-bromotetrazine and establish its reactivity towards nucleophiles leading to the synthesis of several novel classes of 3-monosubstituted s-tetrazines. A remarkable functional group selectivity is observed and is utilised to site-selectively functionalise different compl...

The toxicity of the cyanobacterium Microcystis aeruginosa EAWAG 127a was evaluated against the sensitive grazer Thamnocephalus platyurus, and the extract possessed strong activity. To investigate the compounds responsible for cytotoxicity, a series of peptides from this cyanobacterium were studied using a combined genomic and molecular networking a...

div> We report the synthesis of the novel precursor 3-bromotetrazine and its successful use in the synthesis of various families of 3-monosubstituted s-tetrazines. A remarkable functional group selectivity is utilized to site-selectively functionalize different complex molecules. The unexpected stability of 3- bromotetrazine in aqueous media facil...

Many social behaviours of bacteria are regulated by quorum sensing through the production and perception of structurally diverse signal molecules. The opportunistic pathogen Burkholderia cenocepacia uses classic N-acyl-homoserinlactones and cis-2-unsatturated fatty acids for communication. A recent study has identified an additional signal, valdiaz...

The plant Psychotria kirkii hosts an obligatory bacterial symbiont, Candidatus Burkholderia kirkii, in nodules on their leaves. Recently, a glucosylated derivative of (+)‐streptol, (+)‐streptol glucoside, was isolated from the nodulated leaves and was found to possess a plant growth inhibitory activity. To establish a structure–activity relationshi...

Members of the diazeniumdiolate class of natural compounds show potential for drug development because of their antifungal, antibacterial, antiviral, and antitumor activities. Yet, their biosynthesis has remained elusive to date. Here, we identify a gene cluster directing the biosynthesis of the diazeniumdiolate compound fragin in Burkholderia ceno...

Bacteria of the genus Burkholderia establish an obligate symbiosis with plant species of the Rubiaceae and Primulaceae families. The bacteria, housed within the leaves, are transmitted hereditarily and have not yet been cultured. We have sequenced and compared the genomes of eight bacterial leaf nodule symbionts of the Rubiaceae plant family. All o...

The new C7 N aminocyclitol kirkamide (1) was isolated from leaf nodules of the plant Psychotria kirkii by using a genome-driven (1) H NMR-guided fractionation approach. The structure and absolute configuration were elucidated by HRMS, NMR, and single-crystal X-ray crystallography. An enantioselective total synthesis was developed, which delivered k...

The isolation and structural characterization of three new heterocyclic and macrocyclic peptides, balgacyclamides A-C, from Microcystis aeruginosa EAWAG 251 are reported. The constitutions were determined by 2D-NMR methods and mass spectrometry, and the configurations were assigned after ozonolysis and hydrolysis by HPLC-MS methods using Marfey's m...

Chemical compounds isolated from natural sources offer unique opportunities to understand life on a molecular level. In this account, an overview over different natural products investigated in our research group over the last decade is presented. We have shown that protein localization in living cells can be controlled by anguinomycins and derivat...