Applied and Environmental Microbiology最新文献

{"title":"Modeling of mold inactivation via cold atmospheric plasma (CAP).","authors":"Pavel Demo, Filip Přeučil, Petra Tichá, Mária Domonkos, Eliška Lokajová, Jana Jirešová","doi":"10.1128/aem.02102-24","DOIUrl":"https://doi.org/10.1128/aem.02102-24","url":null,"abstract":"<p><p>During their reproduction cycles, the omnipresent pathogens produce a broad class of mycotoxins responsible for serious health problems in living organisms. To reduce (or even to eradicate) the microorganisms from the invaded system, various conventional methods are applied in practice, sometimes with counterproductive effects. To overcome these challenges, the cold atmospheric plasma (CAP) is applied to terminate mold proliferation within the system. The paper presents a mathematical model for the elimination of microscopic filamentous types of fungi, specifically molds, by using the CAP. The evolution of mold population is described by a nonlinear logistic equation with a density-dependent inactivation rate. Exactly calculated growth curves are compared with experimental data for <i>Aspergillus brasiliensis</i> obtained for two plasma operating times. The results show that if the plasma inactivation rate is comparable to the maximum natural growth rate of the mycelium, the mold colony becomes extinct after a finite time. Otherwise, the mycelium may survive the plasma intervention. The model presented in the paper can be applied to other classes of microorganisms (e.g., bacteria and viruses), using different inactivation techniques (e.g., heating or high pressures with properly defined inactivation rates).</p><p><strong>Importance: </strong>The novelty of this study is to model the extinction process of molds from an invaded system by using a nonlinear logistic equation with a density-dependent inactivation rate. The resulting analytical solution allows us to determine the coverage of the surface by mycelium at arbitrary times. The calculated growth curves are compared with data sets for <i>Aspergillus brasiliensis</i>. An advantage of this model is the possibility to obtain relevant information in a matter of minutes, compared to the highly time-consuming real experiments that can take weeks.</p>","PeriodicalId":8002,"journal":{"name":"Applied and Environmental Microbiology","volume":" ","pages":"e0210224"},"PeriodicalIF":3.9,"publicationDate":"2025-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143778768","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The TetR-like regulator Sco4385 and Crp-like regulator Sco3571 modulate heterologous production of antibiotics in <i>Streptomyces coelicolor</i> M512.","authors":"Sarah Wilcken, Panagiota-Hanna Koutsandrea, Tomke Bakker, Andreas Kulik, Tim Orthwein, Mirita Franz-Wachtel, Theresa Harbig, Kay Katja Nieselt, Karl Forchhammer, Heike Brötz-Oesterhelt, Boris Macek, Silja Mordhorst, Leonard Kaysser, Bertolt Gust","doi":"10.1128/aem.02315-24","DOIUrl":"https://doi.org/10.1128/aem.02315-24","url":null,"abstract":"<p><p>Heterologous expression in well-studied model strains is a routinely applied method to investigate biosynthetic pathways. Here, we pursue a comparative approach of large-scale DNA-affinity-capturing assays (DACAs) coupled with semi-quantitative mass spectrometry (MS) to identify putative regulatory proteins from <i>Streptomyces coelicolor</i> M512, which bind to the heterologously expressed biosynthetic gene clusters (BGCs) of the liponucleoside antibiotics caprazamycin and liposidomycin. Both gene clusters share an almost identical genetic arrangement, including the location of promoter regions, as detected by RNA sequencing. A total of 2,214 proteins were trapped at the predicted promoter regions, with only three binding to corresponding promoters in both gene clusters. Among these, the overexpression of a yet uncharacterized TetR-family regulator (TFR), Sco4385, increased caprazamycin but not liposidomycin production. Protein-DNA interaction experiments using biolayer interferometry confirmed the binding of Sco4385 to P<i>cpz10</i> and P<i>lpmH</i> at different locations within both promoter regions, which might explain its functional variance. Sequence alignment allowed the determination of a consensus sequence present in both promoter regions, to which Sco4385 was experimentally shown to bind. Furthermore, we found that the overexpression of the Crp regulator, Sco3571, leads to a threefold increase in caprazamycin and liposidomycin production yields, possibly due to an increased expression of a precursor pathway.IMPORTANCEStreptomycetes are well-studied model organisms for the biosynthesis of pharmaceutically, industrially, and biotechnologically valuable metabolites. Their naturally broad repertoire of natural products can be further exploited by heterologous expression of biosynthetic gene clusters (BGCs) in non-native host strains. This approach forces the host to adapt to a new regulatory and metabolic environment. In our study, we demonstrate that a host regulator not only interacts with newly incorporated gene clusters but also regulates precursor supply for the produced compounds. We present a comprehensive study of regulatory proteins that interact with two genetically similar gene clusters for the biosynthesis of liponucleoside antibiotics. Thereby, we identified regulators of the heterologous host that influence the production of the corresponding antibiotic. Surprisingly, the regulatory interaction is highly specific for each biosynthetic gene cluster, even though they encode largely structurally similar metabolites.</p>","PeriodicalId":8002,"journal":{"name":"Applied and Environmental Microbiology","volume":" ","pages":"e0231524"},"PeriodicalIF":3.9,"publicationDate":"2025-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143778719","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Improvement of acetate tolerance of <i>Escherichia coli</i> by introducing the PHB mobilization pathway.","authors":"Dong Meng, Shuai Wang, Ke Zhao, Yan Luo, Xu Li, Ying Wang","doi":"10.1128/aem.02454-24","DOIUrl":"https://doi.org/10.1128/aem.02454-24","url":null,"abstract":"<p><p>Poly-β-hydroxybutyrate (PHB) mobilization has been recognized as an effective measure in bacteria for host survival under stressful conditions. Here, we report that PHB mobilization is also involved in improving <i>Escherichia coli</i> resistance to acetic acid stress. Under 0.06% (vol/vol) acetic acid stress, the cell viability of strain M5 with PHB mobilization reached 52.8%, significantly higher than the 25.2% observed for strain M1 without PHB mobilization. Comparison of transcriptome data between M1 and M5 strains identified genes associated with membrane formation that participate in acetic acid tolerance. As a result, the membrane integrity of the M5 strain was significantly increased by 31.5% compared to strain M1. According to physiological membrane analysis, strain M5 showed a 35.3% increase in the ratio of cyclic to unsaturated fatty acids compared to strain M1 under 0.06% (vol/vol) acetic acid. These results indicate that PHB mobilization can regulate membrane components, consequently enhancing cell tolerance to acetic acid. Furthermore, acetate serves as a cost-effective alternative carbon source for microbial cultivation. Then, the succinate-producing strain M8 containing PHB mobilization was used to produce succinate and PHB from sodium acetate. Interestingly, PHB mobilization improved sodium acetate tolerance and utilization in <i>E. coli</i>, while enhancing succinate and PHB production. Finally, strain M8 can accumulate 23.93 g/L succinate and 7.21 g/L PHB using sodium acetate under fed-batch fermentation. In conclusion, this work reveals the role of PHB mobilization under acetate stress and provides a basis for acetate utilization.IMPORTANCEThis study investigated the underlying mechanism through which PHB mobilization enhances <i>Escherichia coli</i> tolerance to acetic acid stress. PHB mobilization improved <i>E. coli</i> tolerance to acetic acid, leading to enhanced cell viability. The transcriptome results indicated that PHB mobilization mainly alters the expression of membrane-associated genes, such as gene <i>Bhsa</i> (encoding outer membrane protein), leading to increased resistance to acetic acid. The membrane physiological analysis indicated that PHB mobilization plays a critical role in membrane integrity, fluidity, and lipid components under acetic acid stress. Moreover, we proposed a novel approach for the co-synthesis of succinate and PHB in recombinant <i>E. coli</i> from sodium acetate. The succinate-producing strain M8 harboring PHB mobilization can efficiently co-produce succinate and PHB, exhibiting better cell growth and sodium acetate utilization compared to the control strain without PHB mobilization. These findings indicate that PHB mobilization has implications for developing robust <i>E. coli</i> and their biosynthesis applications.</p>","PeriodicalId":8002,"journal":{"name":"Applied and Environmental Microbiology","volume":" ","pages":"e0245424"},"PeriodicalIF":3.9,"publicationDate":"2025-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143778763","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Immobilization of alginate C-5 epimerases using <i>Bacillus subtilis</i> spore display.","authors":"Jan Benedict Spannenkrebs, Agnes Beenfeldt Petersen, Finn Lillelund Aachmann, Johannes Kabisch","doi":"10.1128/aem.00298-25","DOIUrl":"https://doi.org/10.1128/aem.00298-25","url":null,"abstract":"<p><p>Alginates are the most abundant polysaccharides found in brown seaweed, composed of (1→4)-linked β-D-mannuronate (M) and its C-5 epimer, α-L-guluronate (G). The G-blocks of alginate possess viscosifying and gelling properties, making alginates valuable industrial polysaccharides. Alginate epimerases are enzymes epimerizing M to G, enhancing the usability and value of alginate. The three alginate epimerases AlgE1, AlgE4, and AlgE6 were immobilized using <i>Bacillus subtilis</i> spores displaying the epimerases fused to the spore crust protein CotY. To our knowledge, this is the first display of immobilized alginate-modifying enzymes. Activity assays of the four AlgE4-displaying spore strains showed that AlgE4 produced MG-blocks from polyM alginate. AlgE4 was tested linked by its N- and C-termini. Two linkers with different flexibility were tested, both containing a TEV protease cleavage site. Immobilizing alginate epimerases on <i>B. subtilis</i> spores resulted in a recyclable system that is easy to isolate and reuse, thus opening possibilities for industrial application. Recyclability was demonstrated by performing five consecutive reactions with the same batch of AlgE4 spores, with the spores retaining 24% of the starting activity after four rounds of reuse. TEV cleavage of spore-displayed enzyme was optimized using spores displaying a green fluorescent protein, and these optimized conditions were used to cleave AlgE4 off the spores. The cleavage of four AlgE4-displaying spores was successful, but cleavage efficiency varied depending on which terminus of AlgE4 was fused to CotY.</p><p><strong>Importance: </strong>Seaweed is a scalable resource that requires no fresh water, fertilizer, or arable land, making it an important biomass for bioeconomies. Alginates are a major component of brown seaweed and are widely used in food, feed, technical, and pharmacological industries. To tailor the functional properties of alginates, alginate epimerases have shown to be promising for postharvest valorization of alginate. This study investigates an efficient and easy method to produce immobilized alginate epimerases, thus opening new industrial use cases. In this study, the alginate epimerases are immobilized on the surface of <i>Bacillus subtilis</i> spores. The bacterium forms spores in reaction to nutrient starvation, which are highly resistant to external influences and can be repurposed as a stable protein display platform for numerous applications due to its ease of genomic manipulation and cultivation.</p>","PeriodicalId":8002,"journal":{"name":"Applied and Environmental Microbiology","volume":" ","pages":"e0029825"},"PeriodicalIF":3.9,"publicationDate":"2025-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143771097","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Polyyne production is regulated by the transcriptional regulators PgnC and GacA in <i>Pseudomonas protegens</i> Pf-5.","authors":"Chiseche Mwanza, Maria Purnamasari, Daniel Back, Cahya Prihatna, Benjamin Philmus, Khaled H Almabruk, Taifo Mahmud, Lumeng Ye, Melvin D Bolton, Xiaogang Wu, Joyce E Loper, Qing Yan","doi":"10.1128/aem.02388-24","DOIUrl":"https://doi.org/10.1128/aem.02388-24","url":null,"abstract":"<p><p>Polyynes produced by bacteria have promising applications in agriculture and medicine due to their potent antimicrobial activities. Polyyne biosynthetic genes have been identified in <i>Pseudomonas</i> and <i>Burkholderia</i>. However, the molecular mechanisms underlying the regulation of polyyne biosynthesis remain largely unknown. In this study, we used a soil bacterium <i>Pseudomonas protegens</i> Pf-5, which was recently reported to produce polyyne called protegenin, as a model to investigate the regulation of bacterial polyyne production. Our results show that Pf-5 controls polyyne production at both the pathway-specific level and a higher global level. Mutation of <i>pgnC</i>, a transcriptional regulatory gene located in the polyyne biosynthetic gene cluster, abolished polyyne production. Gene expression analysis revealed that PgnC directly activates the promoter of polyyne biosynthetic genes. The production of polyyne also requires a global regulator GacA. Mutation of <i>gacA</i> decreased the translation of PgnC, which is consistent with the result that <i>pgnC</i> leader mRNA bound directly to RsmE, an RNA-binding protein negatively regulated by GacA. These results suggest that GacA induces the expression of the PgnC regulator, which in turn activates polyyne biosynthesis. Additionally, the polyyne-producing strain of Pf-5, but not the polyyne-nonproducing strain, could inhibit a broad spectrum of bacteria including both Gram-negative and Gram-positive bacteria.IMPORTANCEAntimicrobial metabolites produced by bacteria are widely used in agriculture and medicine to control plant, animal, and human pathogens. Although bacteria-derived polyynes have been identified as potent antimicrobials for decades, the molecular mechanisms by which bacteria regulate polyyne biosynthesis remain understudied. In this study, we found that polyyne biosynthesis is directly activated by a pathway-specific regulator PgnC, which is induced by a global regulator GacA through the RNA-binding protein RsmE in <i>Pseudomonas protegens</i>. To our knowledge, this work is the first comprehensive study of the regulatory mechanisms of bacterial polyyne biosynthesis at both pathway-specific level and global level. The discovered molecular mechanisms can help us optimize polyyne production for agricultural or medical applications.</p>","PeriodicalId":8002,"journal":{"name":"Applied and Environmental Microbiology","volume":" ","pages":"e0238824"},"PeriodicalIF":3.9,"publicationDate":"2025-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143771099","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Fresh pork microbiota is temporally dynamic and compositionally diverse across meat, contact surfaces, and processing lines in a pork processing facility.","authors":"A E Asmus, T N Gaire, K M Heimer, K E Belk, R S Singer, T J Johnson, N R Noyes","doi":"10.1128/aem.00044-25","DOIUrl":"https://doi.org/10.1128/aem.00044-25","url":null,"abstract":"<p><p>The goal of this study was to analyze the microbial profiles of meat and contact surfaces from two different processing lines in a pork processing plant, using a 16S rRNA gene amplicon sequencing workflow specifically designed to investigate fresh meat and environmental samples throughout a commercial production schedule. Results indicated that the microbiota differed between the meat and contact surface, both across the two processing lines and within each individual processing line. Differences in the microbiota composition were also strongly associated with both the specific processing dates and the time of day during processing. Much of this variation was associated with distinct amplicon sequence variants unique to each processing date and each processing line throughout the day. The abundance of key taxa associated with food safety and spoilage was also temporally dynamic across a production shift and was different between the meat and contact surface. Overall, the results of this study indicate significant differences in the microbial profiles of the meat and contact surfaces between two processing lines within the same plant. These differences are likely influenced by daily variation in processing and sanitation procedures, as well as differences in the design of the processing lines, which appear to affect the microbiotas of both the meat and contact surfaces.IMPORTANCEThis study provides critical knowledge that can be used as a foundation for tailored processes to improve fresh pork safety and quality, potentially customized to individual processing lines, time points within a shift, and/or production days. Additionally, this study provides a list of potential biological markers associated with food safety and quality that could be used by processors to develop and validate intervention strategies specific to different processing lines.</p>","PeriodicalId":8002,"journal":{"name":"Applied and Environmental Microbiology","volume":" ","pages":"e0004425"},"PeriodicalIF":3.9,"publicationDate":"2025-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143771094","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A dynamic protein interactome drives energy conservation and electron flux in <i>Thermococcus kodakarensis</i>.","authors":"Sere A Williams, Danielle M Riley, Teagan P Rockwood, David A Crosby, Katherine D Call, Jared J LeCuyer, Thomas J Santangelo","doi":"10.1128/aem.00293-25","DOIUrl":"https://doi.org/10.1128/aem.00293-25","url":null,"abstract":"<p><p>Life is supported by energy gains fueled by catabolism of a wide range of substrates, each reliant on the selective partitioning of electrons through redox (<u>red</u>uction and <u>ox</u>idation) reactions. Electron flux through tunable and regulated protein interactions provides dynamic routes for energy conservation, but how electron flux is regulated <i>in vivo</i>, particularly for archaeal metabolisms that support rapid growth at the thermodynamic limits of life, is poorly understood. Identification of <i>bona fide in vivo</i> protein assemblies and how such assemblies dictate the totality of electron flux is critical to our understanding of the regulation imposed on metabolism, energy production, and energy conservation. Here, 25 key proteins in central metabolic redox pathways in the model, genetically accessible, hyperthermophilic archaeon <i>Thermococcus kodakarensis</i>, were purified to reveal an extensive, dynamic, and tightly interconnected network of protein interactions that responds to environmental cues (such as the availability of various reductive sinks) to direct electron flux to maximize energetic gains. Interactions connecting disparate functions suggest many catabolic and anabolic activities occur in spatial proximity <i>in vivo</i>, and while protein complexes have been historically defined under optimal conditions, many of these complexes appear to maintain alternative partnerships in changing conditions. The totality of the results obtained redefines our understanding of <i>in vivo</i> assemblies driving ancient metabolic strategies supporting the growth of modern Archaea.IMPORTANCEGiven the potential for rational genetic manipulations of biofuel- and biotech-promising archaea to yield transformative results for major markets, it is a priority to define how the metabolisms of such species are controlled, at least in part, by <i>in vivo</i> protein assemblies, and from such, define routes of energy flux that can be most efficiently altered toward biofuel or biotechnological gains. Proteinaceous electron carriers (PECs, such as ferredoxins) offer the potential for specific protein-protein interactions to coordinate selective reductive flow. Employing the model, genetically accessible, hyperthermophilic archaeon, <i>Thermococcus kodakarensis</i>, we establish the metabolic protein interactome of 25 key redox proteins, revealing that each redox active protein has a dynamic partnership profile, suggesting catabolic and anabolic activities may occur in concert and in temporal and spatial proximity <i>in vivo</i>. These results reveal critical importance in evaluating the newly identified partnerships and their role and utility in providing regulated redox flux in <i>T. kodakarensis</i>.</p>","PeriodicalId":8002,"journal":{"name":"Applied and Environmental Microbiology","volume":" ","pages":"e0029325"},"PeriodicalIF":3.9,"publicationDate":"2025-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143770952","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Antimicrobial peptides: from discovery to developmental applications.","authors":"Qi Zhang","doi":"10.1128/aem.02115-24","DOIUrl":"https://doi.org/10.1128/aem.02115-24","url":null,"abstract":"<p><p>Antimicrobial resistance (AMR) has emerged as a significant crisis in global health. Due to their advantageous properties, antimicrobial peptides (AMPs) have garnered considerable attention as a potential alternative therapy to address the AMR crisis. These peptides might disrupt cell membranes or cell walls to exhibit antimicrobial activity, or modulate the immune response to promote recovery from diseases. In recent years, significant progress has been made in the research of AMPs, alongside the emergence of new challenges. This review first systematically summarizes and critically discusses recent advancements in understanding the characteristics and current landscapes of AMPs, as well as their regulatory mechanisms of action and practical applications, particularly those reported or approved within the last 5 years. Additionally, the principles, paths for their identification, and future research trends in AMPs are also analyzed following a discussion of the advantages and disadvantages of AMPs in comparison to conventional antibiotics. Unlike significant prior literature in this field, this report has summarized the latest major discovery methods for AMPs and, more importantly, emphasized their practical applications by supporting various viewpoints using selected examples of AMPs' applications in real-life scenarios. Besides, some emerging hot topics of AMPs, including those derived from gut microbiota and their potential synergistic effects in combating AMR, were profiled. All of these indicate the originality of the report and provide valuable references for future AMP discoveries and applications.</p>","PeriodicalId":8002,"journal":{"name":"Applied and Environmental Microbiology","volume":" ","pages":"e0211524"},"PeriodicalIF":3.9,"publicationDate":"2025-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143770959","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Anaerobic degradation of polycyclic aromatic hydrocarbons.","authors":"Isabelle Heker, Nadia A Samak, Yachao Kong, Rainer U Meckenstock","doi":"10.1128/aem.02268-24","DOIUrl":"https://doi.org/10.1128/aem.02268-24","url":null,"abstract":"<p><p>Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous and toxic pollutants in the environment that are mostly introduced through anthropogenic activities. They are very stable with low bioavailability and, because aerobic degradation is mostly limited in aquifers and sediments, often persist in anoxic systems. In this review, we elucidate the recent advances in PAH degradation by anaerobic, mostly sulfate-reducing cultures. The best-studied compound is naphthalene, the smallest and simplest PAH, which often serves as a model compound for anaerobic PAH degradation. In recent years, three-ring PAHs have also shifted into focus, using phenanthrene as a representative compound. Anaerobic degradation of PAHs has to overcome several biochemical problems. First, non-substituted PAHs have to be activated by carboxylation, which is chemically challenging and proposed to involve a 1,3-cycloaddition with a UbiD-like carboxylase and a prenylated flavin cofactor. The second key reaction is to overcome the resonance energy of the ring system, which is performed by consecutive two-electron reduction steps involving novel type III aryl-CoA reductases belonging to the old-yellow enzyme family. In naphthalene degradation, a type I aryl-CoA reductase is also involved in reducing a benzene ring structure. The third key reaction is the ring cleavage, involving β-oxidation-like reactions in cleaving ring I of naphthalene. Ring II, however, is opened by a novel lyase reaction at a tertiary, hydroxylated carbon atom. These principles are explained using examples of anaerobic naphthalene and phenanthrene degradation to give an overview of recent advances, from the initial activation of the molecules to the complete degradation to CO₂.</p>","PeriodicalId":8002,"journal":{"name":"Applied and Environmental Microbiology","volume":" ","pages":"e0226824"},"PeriodicalIF":3.9,"publicationDate":"2025-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143762875","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Discovery of two novel cutinases from a gut yeast of plastic-eating mealworm for polyester depolymerization.","authors":"Tong Huang, Jingya Zhang, Xuena Dong, Yu Yang","doi":"10.1128/aem.02562-24","DOIUrl":"https://doi.org/10.1128/aem.02562-24","url":null,"abstract":"<p><p>Identification of novel plastic-degrading enzymes is crucial for developing enzymatic degradation and recycling strategies for plastic waste. Here, we report the discovery of two novel cutinases, SiCut1 and SiCut2, from a yeast strain <i>Sakaguchia</i> sp. BIT-D3 was isolated from the gut of plastic-eating mealworms. Their amino acid sequences share less than 25% identity with all previously described cutinases and reveal a conserved S-D-H catalytic triad with a unique GYSKG motif. Their recombinant proteins were successfully overexpressed in <i>Pichia pastoris</i>. The pH range for both enzymes was 4.0 to 11.0 and the temperature range for SiCut1 and SiCut2 was 10°C to 50°C and 10°C to 70°C, respectively. Both enzymes showed strong activity against apple cutin and short-chain fatty acid esters of <i>p</i>-nitrophenol and glycerol, substantiating their classification as true cutinases. SiCut1 and SiCut2 have been demonstrated to exhibit efficient degradation of polycaprolactone (PCL) film, polybutylene succinate (PBS) film, and polyester-polyurethane (PUR) foam. Molecular docking and molecular dynamics simulations were used to elucidate the underlying mechanisms of the observed catalytic activity and thermal stability. This study shows that SiCut1 and SiCut2 are novel yeast-derived cutinases with the potential for depolymerization and recycling of plastic waste.IMPORTANCEThe identification of novel plastic-degrading enzymes is critical in addressing the pervasive problem of plastic pollution. This study presents two unique cutinases, SiCut1 and SiCut2, derived from the yeast <i>Sakaguchia</i> sp. BIT-D3 isolated from the gut of plastic-feeding mealworms. Despite sharing less than 25% sequence identity with known cutinases, both enzymes exhibit remarkable degradation capabilities against various polyester plastics, including polycaprolactone (PCL) film, polybutylene succinate (PBS) film, and polyester-polyurethane (PUR) foam. Our results elucidate the catalytic mechanisms of SiCut1 and SiCut2 and provide insights into their potential applications in enzymatic degradation and recycling strategies. By harnessing the gut microbiota of plastic-degrading organisms, this research lays the foundation for innovative enzyme-based solutions to reduce plastic waste and promote sustainable practices in waste management.</p>","PeriodicalId":8002,"journal":{"name":"Applied and Environmental Microbiology","volume":" ","pages":"e0256224"},"PeriodicalIF":3.9,"publicationDate":"2025-04-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143762513","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}