Biology subjects

Steiner, T.

Publications and source records attributed to Steiner, T..

8 recordsLinked to original sources

bioRxiv2025

Engineered symbiont biosensor maps micron-scale sugar gradients in the honeybee gut

The honeybee gut microbiota plays a key role in shaping host health and susceptibility to disease. Yet, the nutrient environment it experiences within the gut remains poorly characterized. In particular, little is known about the spatial distribution of nutrients across this community, as resolving such fine gradients in vivo has been technically challenging. Here, we engineer the native honeybee symbiont Snodgrassella alvi as a living biosensor to quantify the bioavailability of the dietary sugar arabinose within the gut. By expanding the genetic toolkit for S. alvi through chromosomal integration of high-burden genes and a suite of low-strength promoters, we achieve stable multi-gene expression without compromising host colonization. The resulting biosensor generates a specific, dose-dependent response to arabinose in situ, enabling visualization of sugar gradients across gut-associated bacterial biofilms at micron-scale resolution. Using this system, we show that diet-derived arabinose distribution is highly heterogeneous and can be influenced by the metabolic activity of co-colonizing Gilliamella species. These findings highlight how diet composition and microbial specialization generate fine-scale microenvironments within the gut. More broadly, this work further establishes S. alvi as a genetically tractable platform for in situ probing of microbial metabolism and nutrient distribution.

synthetic biology↗

bioRxiv2024

Engineering microbial consortia: uptake and leakage ratedifferentially shape community arrangement and composition

Bacteria often grow as communities in intricate spatial arrangements on surfaces and interact with each other through the local exchange of diffusible molecules. Yet, our understanding of how these interactions shape the properties of the communities remains limited. Here, we study synthetic communities of Escherichia coli amino acid auxotrophs interacting through the obligate exchange of amino acids. We genetically engineer these strains to alter their amino acid leakage and uptake abilities. We then characterise the spatial arrangement and composition of the communities when grown on a surface. By integrating experimental data with mathematical modeling, we demonstrate that amino acid uptake and leakage rates are crucial determinants of community structure. Our results show that while the spatial arrangement of the community is primarily governed by uptake rates, the community composition is predominantly influenced by leakage rates. These findings enhance our understanding of microbial community dynamics and provide a framework for predicting and engineering microbial consortia.

microbiology↗

bioRxiv2024

Signal Antagonists Suppress Pseudomonas syringae Pathogenicity

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 attractive treatment strategy would involve antagonists that suppress the expression of virulence factors without killing the pathogen, potentially reducing the risk of resistance development. Herein, we present the design and synthesis of analogs of leudiazen, which positively regulates the production of mangotoxin in P. syringae pv. syringae (Pss). Several compounds display inhibitory activity towards mangotoxin production, and a lead compound abolishes necrosis in infected tomato leaves, without significantly affecting bacterial growth. Thus, this study represents a promising advance towards developing effective and sustainable methods for bacterial disease control.

microbiology↗

bioRxiv2022

The large GTPase Sey1/atlastin mediates lipid droplet- and FadL-dependent intracellular fatty acid metabolism of Legionella pneumophila

The facultative intracellular bacterium Legionella pneumophila employs the Icm/Dot type IV secretion system (T4SS) to replicate in a unique membrane-bound compartment, the Legionella-containing vacuole (LCV). The endoplasmic reticulum (ER)-resident large fusion GTPase Sey1/atlastin promotes remodeling and expansion of LCVs, and the GTPase is also implicated in the formation of ER-derived lipid droplets (LDs). Here we show that LCVs intimately interact with palmitate-induced LDs in Dictyostelium discoideum amoeba. Comparative proteomics of LDs isolated from the D. discoideum parental strain Ax3 or {otimes}sey1 revealed 144 differentially produced proteins, of which 7 or 22 were exclusively detected in LDs isolated from strain Ax3 or {otimes}sey1, respectively. Using dually fluorescence-labeled amoeba producing the LCV marker P4C-GFP or AmtA-GFP and the LD marker mCherry-perilipin, we discovered that Sey1 and the L. pneumophila Icm/Dot T4SS as well as the effector LegG1 promote LCV-LD interactions. In vitro reconstitution of the LCV-LD interactions using purified LCVs and LDs from D. discoideum Ax3 or {otimes}sey1 revealed that Sey1 and GTP promote this process. The LCV-LD interactions were impaired for {otimes}sey1-derived LDs, suggesting that Sey1 regulates LD composition. Palmitate promoted the growth of (i) L. pneumophila wild-type in D. discoideum Ax3 but not in {otimes}sey1 mutant amoeba and (ii) L. pneumophila wild-type but not {otimes}fadL mutant bacteria lacking a homologue of the E. coli fatty acid transporter FadL. Finally, isotopologue profiling indicated that intracellular L. pneumophila metabolizes 13C-palmitate, and its catabolism was reduced in D. discoideum {otimes}sey1 and L. pneumophila {otimes}fadL. Taken together, our results reveal that Sey1 mediates LD- and FadL-dependent fatty acid metabolism of intracellular L. pneumophila.

microbiology↗

bioRxiv2022

A central role of sibling sRNAs NgncR_162/163 in main metabolic pathways of Neisseria gonorrhoeae

Bacterial regulatory RNAs (sRNAs) have been implicated in the regulation of numerous metabolic pathways. In most of these studies, sRNA-dependent regulation of mRNAs or proteins of enzymes in metabolic pathways has been predicted to affect the metabolism of these bacteria. However, only in very few cases has the role in metabolism been demonstrated. We performed here a combined transcriptome and metabolome analysis to define the regulon of the sibling sRNAs NgncR_162 and NgncR_163 and their impact on the metabolism of the major human pathogen Neisseria gonorrhoeae. These sRNA have previously been shown to control genes of the citric acid and methylcitrate cycle by post-transcriptional negative regulation. By transcriptome analysis we expand the NgncR_162/163 regulon by several new members and provide evidence that the sibling sRNAs act as both negative and positive regulators of target gene expression. Newly identified NgncR_162/163 targets are mostly involved in transport processes, especially the uptake of glycine, branched chain amino acids and phenylalanine. NgncR_162/163 also play key roles in the control of serine-glycine metabolism and hence probably affect biosynthesis of nucleotides, vitamins and other amino acids via the supply of C1-units. Metabolic flux analysis demonstrated a bipartite metabolism with glucose degradation providing intermediates for anabolic pathways, while energy metabolism via the citric acid cycle is mainly driven by amino acids, which feed into the cycle. Thus, by combined RNA-seq and metabolomics we significantly extended the regulon of NgncR_162/163 and demonstrate their role in the regulation of central metabolic pathways of the gonococcus. ImportanceNeisseria gonorrhoeae is a major human pathogen which infects more than 100 million people every year. An alarming development is the emergence of gonococcal strains resistant against virtually all of the antibiotics used for their treatment. Despite the medical importance and the vanishing treatment options of gonococcal infections, the bacterial metabolism and its regulation is only ill defined until today. We investigate here the regulation of the gonococcal metabolism by two previously studied sRNAs, NgncR_162/163 using RNA-seq and metabolomics. The results provided in this study demonstrate the regulation of transport processes and metabolic pathways involved in the biosynthesis of nucleotides, vitamins and amino acids by NgncR_162/163. Combined transcriptome and metabolome analyses provide a thus far unreached depth in the regulation of metabolic pathways by the neisserial sibling sRNAs and may therefore also be suitable for functional analysis of a growing number of other bacterial metabolic sRNA regulators.

microbiology↗

bioRxiv2021

IHF regulates host colonization factors in the bee gut symbiont Frischella perrara

Bacteria colonize specific niches in the animal gut. However, the genetic basis of these associations is often unclear. The proteobacterium Frischella perrara is a widely distributed gut symbiont of honey bees. It colonizes a specific niche in the hindgut and causes a characteristic melanization response. Genetic determinants required for the establishment of this association, or its relevance for the host, are unknown. Here, we independently isolated three point mutations in genes encoding the DNA-binding protein integration host factor (IHF) in F. perrara. These mutants abolished the production of an aryl polyene metabolite causing the yellow colony morphotype of F. perrara. Inoculation of microbiota-free bees with one of the mutants drastically decreased gut colonization of F. perrara. Using RNAseq we found that IHF affects the expression of potential colonization factors, including genes for adhesion (Type 4 pili), interbacterial competition (Type 6 secretion systems), and secondary metabolite production (colibactin and aryl polyene biosynthesis). Gene deletions of these components revealed different colonization defects depending on the presence of other bee gut bacteria. Interestingly, one of the T6SS mutants did not induce the scab phenotype anymore, despite colonizing at high levels, suggesting an unexpected role in bacteria-host interaction. IHF is conserved across many bacteria and may also regulate host colonization in other animal symbionts.

microbiology↗

bioRxiv2021

A novel highly potent inhibitor of TMPRSS2-like proteases blocks SARS-CoV-2 variants of concern and is broadly protective against infection and mortality in mice

The COVID-19 pandemic caused by the SARS-CoV-2 virus remains a global public health crisis. Although widespread vaccination campaigns are underway, their efficacy is reduced against emerging variants of concern (VOCs) 1,2. Development of host-directed therapeutics and prophylactics could limit such resistance and offer urgently needed protection against VOCs 3,4. Attractive pharmacological targets to impede viral entry include type-II transmembrane serine proteases (TTSPs), such as TMPRSS2, whose essential role in the virus lifecycle is responsible for the cleavage and priming of the viral spike protein 5-7. Here, we identify and characterize a small-molecule compound, N-0385, as the most potent inhibitor of TMPRSS2 reported to date. N-0385 exhibited low nanomolar potency and a selectivity index of >106 at inhibiting SARS-CoV-2 infection in human lung cells and in donor-derived colonoids 8. Importantly, N-0385 acted as a broad-spectrum coronavirus inhibitor of two SARS-CoV-2 VOCs, B.1.1.7 and B.1.351. Strikingly, single daily intranasal administration of N-0385 early in infection significantly improved weight loss and clinical outcomes, and yielded 100% survival in the severe K18-human ACE2 transgenic mouse model of SARS-CoV-2 disease. This demonstrates that TTSP-mediated proteolytic maturation of spike is critical for SARS-CoV-2 infection in vivo and suggests that N-0385 provides a novel effective early treatment option against COVID-19 and emerging SARS-CoV-2 VOCs.

microbiology↗

bioRxiv2020

Shark movements in the Revillagigedo Archipelago and connectivity with the Eastern Tropical Pacific

Long-distance movements of sharks within and between islands pose substantial challenges for resource managers working with highly migratory species. When no-take zones do not cover the critical areas that sharks use as part of their lifecycle, exposure to fishing activities can be significant. Shark movements between the Marine Protected Areas (MPAs) of the Eastern Tropical Pacific (ETP) have been studied for several years, however little is known about the strength of connectivity between these islands. We analyzed the extensive MigraMar ultrasonic telemetry dataset to assess how Galapagos sharks (Carcharhinus galapagensis) and silky sharks (Carcharhinus falciformis) use different islands as stepping-stones during their migrations within the Revillagigedo National Park and other ETP islands. Of the 66 sharks monitored, 63.5% moved within the same island, 25.4% between two islands or more and only 10.1% across different MPAs. A C. falciformis tagged in Roca Partida Island, Revillagigedo, travelled to Clipperton Atoll and another one tagged in Darwin Island travelled to the atoll on two different years. The largest movement of C. galapagensis was accomplished by a shark tagged at Socorro Island, Revillagigedo, later detected at Clipperton and finally recorded in Darwin Island, Galapagos. This last path was in fact, one of the longest movements ever recorded for the species. Although long-distance dispersion was not common, our results highlight the need for co-operation between different countries to ensure adequate protection for sharks in the form of swimways and other conservation tools in the ETP.

ecology↗