Biology subjects

Streit, W. R.

Publications and source records attributed to Streit, W. R..

6 recordsLinked to original sources

bioRxiv2025

Role of Dienelactone Hydrolases in PET Biodegradation by Flavobacteria Maribacter dokdonensis and Arenibacter palladensis

Dienelactone hydrolases (DLHs, EC 3.1.1.45) are enzymes that play a crucial role in the breakdown of cyclic esters and some have been found to act on substrates such as terephthalate esters, which are monomers of polyethylene terephthalate (PET). In the current study, we show that bacteria affiliated with the Bacteroidota (class Flavobacteria) harbor DLHs acting on PET foil and powder. We report on the isolation of two marine bacterial strains, Arenibacter palladensis UHH-Hm9b and Maribacter dokdonensis UHH-5R5, forming biofilms on PET foil and releasing {micro}M amounts of terephthalic acid after 5-7 days. Genome sequencing and functional analyses identified two secreted DHLs designated PET93 and PET 94 involved in PET degradation. While their predicted active sites and substrates binding pockets were identical to previously published PETases, both enzymes differed largely in their structural features from known PETases and represent novel scaffolds. Further they lacked the typical porC-domain of the known PETases from the Flavobacteria. Biochemical characterization of the two recombinant enzymes confirmed activity on PET, the primary degradation products Bis(2-Hydroxyethyl) terephthalate (BHET) and Mono-(Hydroxyethyl) terephthalate (MHET). These are the first DLHs to be reported being active on plastics and our findings indicate that Flavobacteria harbor an unexpectedly wide range of PET-active promiscuous enzymes. IMPORTANCEGlobal plastics pollution is a major environmental challenge, and we still have limited knowledge of marine microbiota involved in possible remediation. Our research shows that marine Flavobacteria harbor the potential for PET degradation using dienelactone hydrolases (DLHs, EC 3.1.1.45). The widespread distribution of these microorganisms and the notion that these enzymes are secreted may imply a possible role in marine PET remediation.

microbiology↗

bioRxiv2025

A Combined Chemo-Enzymatic Treatment for the Oxidation of Epoxy-Based Carbon Fiber-Reinforced Polymers (CFRPs)

Carbon fiber-reinforced polymers (CFRPs), particularly epoxy-based composites, have become essential in the aerospace, automotive, and wind energy industries due to their robust mechanical properties, and lightweight nature. However, there is a lack of recycling technologies that are environmentally sustainable while also ensuring the recovery of carbon fibers in their original state. Although certain bacterial and fungal strains can colonize epoxy polymers, enzymes capable of efficiently degrading these materials have not yet been reported. Consequently, there is an urgent need for an effective, sustainable, and biologically inspired solution for CFRP recycling. Here, a chemo-enzymatic two-step oxidation process was developed. A chemical pre-treatment with propionic acid and hydrogen peroxide was used to recover imbedded carbon fibers. Additionally, three novel bacterial laccases isolated from the European spruce bark beetle (Ips typographus) demonstrated the ability to degrade three epoxy resin scaffolds from Hexflow(R) RTM6, used in aircraft applications. The sequential combination of both oxidative steps enabled the retrieval of clean carbon fibers and partial modification of epoxy functional groups, with the release of defined products over time. This bio-inspired approach renders the process more environmentally friendly and marks an initial step toward developing a bio-based recycling method for epoxy CFRPs.

biochemistry↗

bioRxiv2025

A Novel Approach to Combat Pseudomonas aeruginosa: Repurposing Pharmaceuticals for Inhibition of Phospholipase A

Phospholipases A (PLAs) play critical roles in cellular physiology, making human PLAs established drug targets. On the other hand, the potential of bacterial PLAs as targets for antimicrobial drug development remains underexplored. In this study, we curated a library of 23 approved and investigational pharmaceuticals, some of which inhibit human PLA-like enzymes, through a combination of ligand structure-based searches and textual mining in literature and compound databases. Experimental screening identified that compounds GW4869, darapladib, and rilapladib significantly inhibit Pseudomonas aeruginosa growth by more than 50 %. While these compounds did not reduce biofilm formation, GW4869 increased the proportion of dead cells in established biofilms, suggesting its role in compromising biofilm cell viability. Biochemical assays revealed that all three compounds inhibited the enzymatic activity of PlaF, a PLA virulence factor of P. aeruginosa, by decreasing the affinity of a model substrate. Molecular dynamics simulations and binding free energy analyses indicate that GW4869 binds to the substrate-binding and product-release tunnels of PlaF, suggesting GW4869 as a non-covalent competitive inhibitor. Notably, the mutant strain P. aeruginosa {Delta}plaF proved to be GW4869 resistant and did not display differential growth upon GW4869 treatment, further indicating PlaF as the primary GW4869 target. Furthermore, GW4869 and rilapladib significantly enhanced the efficacy of the last-resort antibiotic imipenem in combination treatments. These findings highlight the potential of GW4869, darapladib, and rilapladib to act as repurposed inhibitors of PlaF or PLA-dependent mechanisms in P. aeruginosa and underscore the promise of combination therapies against intracellular PLAs to combat antimicrobial resistance.

molecular biology↗

bioRxiv2024

Suspended and sinking particle-associated microbiomesexhibit distinct lifestyles in the Elbe estuary

Estuaries are important components of the global carbon cycle; exchanging carbon between aquatic, atmospheric, and terrestrial environments, representing important loci for blue carbon storage and greenhouse gas emissions. Estuarine particles are especially important due to their microbial transformation and vertical/horizontal transport. We used metagenomes and metatranscriptomes to assess changes in microbial community composition and functions across the Elbe estuary over one year, linking changes to dissolved and particulate organic matter. We will be the first to link microbial activity derived from molecular data to particulate and dissolved organic carbon characteristics. There were no microbial species responses to the measured physicochemical and dissolved/particulate organic matter parameters, however Weighted Correlation Network Analyses showed significant spatial microbiome differences linked to the estuarine salinity profile. Meanwhile, suspended and sinking particle fractions did not show any community wide differences, but individual gene analyses revealed clear microbial lifestyle differences. Sinking particle-associated transcripts highly expressed competition and stress-responses genes, while suspended particle-associated transcripts favoured energy acquisition and growth. Transcription patterns further indicate that suspended particles may represent a mitigating influence on methane release via methanotrophy, while both suspended and sinking particles produce methane through the same gene complex. This notion suggests that increased sinking particle abundance, such as under high turbidity conditions, leads to increased methane production. Our findings further imply that urban activities such as dredging may have a high impact on greenhouse gas emissions, and higher suspended-sinking particle ratios may alleviate aquatic-atmospheric methane exchanges. Future studies should explore in detail the underlying mechanisms and controlling variables, in particular when taking predicted global changes into account.

ecology↗

bioRxiv2024

Environmental controls of dark CO2 fixation in wetland microbiomes

Rising atmospheric concentration of CO2 is a major concern to society due to its global warming potential. In soils, CO2 fixing microorganisms are preventing a part of the CO2 from entering the atmosphere. Yet, the pathways behind dark CO2 fixation are rarely studied in situ. Here we examined the environmental controls on the abundance and expression of key genes involved in microbial CO2 fixation in estuarine wetlands. A combined multi-omics approach incorporating metabarcoding, deep metagenomic and metatranscriptomic analyses confirmed that wetland microbiota harbor all six known CO2 fixation pathways and that these pathways are transcribed at high frequencies along several environmental gradients, albeit at different levels depending on the environmental niche. Notably, the transcription of the key genes for the reductive tricarboxylic acid cycle (rTCA) and the Calvin cycle were favored by low salinity and O2 rich niches high in organic matter, while the transcription of the key genes for the Wood-Ljungdahl pathway (WLP) and dicarboxylate/4-hydroxybutyrate cycle (DC/4-HB cycle) were favored by low O2 niches poor in organic matter. Taxonomic assignment of transcripts implied that dark CO2 fixation was mainly linked to few bacterial phyla, namely, Desulfobacterota, Gemmatimonadota, Methylomirabilota, Nitrospirota and Pseudomonadota.

microbiology↗

bioRxiv2022

The first archaeal PET-degrading enzyme belongs to the feruloyl-esterase family

Polyethylene terephthalate (PET) is a commodity polymer known to globally contaminate marine and terrestrial environments. Today, around 40 bacterial and fungal PET-active enzymes (PETases) are known, originating from four bacterial and two fungal phyla. In contrast, no archaeal enzyme has been identified to degrade PET. Here we report on the structural and biochemical characterization of PET46, an archaeal promiscuous feruloyl esterase exhibiting degradation activitiy on PET, bis-, and mono-(2-hydroxyethyl) terephthalate (BHET and MHET). The enzyme, found by a sequence-based metagenome search, was derived from a non-cultivated, deep-sea Candidatus Bathyarchaeota archaeon. Biochemical characterization demonstrated that PET46 is a promiscuous, heat-adapted hydrolase. Its crystal structure was solved at a resolution of 1.71 [A]. It shares the core alpha/beta-hydrolase fold with bacterial PETases, but contains a unique lid common in feruloyl esterases, which is involved in substrate binding. Thus, our study significantly widens the currently known diversity of PET-hydrolyzing enzymes, by demonstrating PET depolymerization by a lignin-degrading esterase.

biochemistry↗