Applied and Environmental Microbiology最新文献

{"title":"Spatiotemporal patterns of soil myxomycetes in subtropical managed forests and their potential interactions with bacteria.","authors":"Wen-Long Song, Di Lin, Xia Chen, Qun Dai, Gu Rao, Ya-Jing Chen, Shuang-Lin Chen","doi":"10.1128/aem.00479-25","DOIUrl":"https://doi.org/10.1128/aem.00479-25","url":null,"abstract":"<p><p>Soil myxomycetes are crucial soil protists with important ecological functions. Yet, our understanding of their diversity patterns in managed forests and the interactions with their food is far behind other taxa. This study investigates the spatiotemporal patterns of soil myxomycetes in four northern subtropical managed forest types across seasons and aims to identify assembly processes, main predictors of myxomycete communities, and the potential interactions between myxomycetes and bacteria. Results showed that no significant difference in α diversity of myxomycete communities among forest types was observed, but a significant difference was observed in community structures. Significant differences were observed in α diversity and community structures of myxomycetes among seasons. Deterministic processes in each forest type and season dominated myxomycete community assemblies. Soil physicochemical properties and bacterial communities have a significant direct impact on the myxomycete community, while forest types, seasons, and enzyme activities have an indirect effect. There is a significant synergistic covariation between the soil myxomycete community and bacterial community. The genera of the phyla Acidobacteriota, Actinobacteriota, and Bacteroidota have a strong correlation with the richness of myxomycete genera. Overall, this study provides new insight into the diversity of soil myxomycetes and their influence by bacteria, crucial for myxomycetes ecology.IMPORTANCESoil myxomycetes are an important component of soil protists. Our study revealed for the first time the community structure of soil myxomycetes in managed forests of the northern subtropical regions and systematically investigated the seasonal variation patterns of soil myxomycetes. Meanwhile, we further investigated the potential interactions between soil myxomycetes and bacteria. This study will greatly enhance our understanding of the ecology of soil myxomycetes and their biological roles.</p>","PeriodicalId":8002,"journal":{"name":"Applied and Environmental Microbiology","volume":" ","pages":"e0047925"},"PeriodicalIF":3.9,"publicationDate":"2025-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143957990","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":"Identification of factors limiting the efficiency of transplanting extracellular electron transfer chains in <i>Escherichia coli</i>.","authors":"Laura-Alina Philipp, Lukas Kneuer, Carina Mayer-Windhorst, Simon Jautelat, Nhat Quang Le, Johannes Gescher","doi":"10.1128/aem.00685-25","DOIUrl":"https://doi.org/10.1128/aem.00685-25","url":null,"abstract":"<p><p>Research in electro-microbiology provides unique opportunities to study and exploit microbial physiology. Several efforts have been made to transplant the extracellular electron transport chain from the native exoelectrogenic model organism <i>Shewanella oneidensis</i> into <i>Escherichia coli</i>. However, systematic comparisons between donor and recipient strain configurations are largely missing. Hence, the proposed minimal protein set, consisting of the <i>c</i>-type cytochromes cytoplasmic membrane protein A (CymA), small tetraheme cytochrome (STC), MtrA, and MtrC, as well as the <i>β</i>-barrel protein MtrB, was heterologously expressed in <i>E. coli</i> in different expansion stages. These stages were compared to corresponding <i>S. oneidensis</i> strains in terms of anthraquinone-2,6-disulfonate (AQDS) and ferric citrate reduction rates. This revealed that transplantation of heterologous extracellular electron transfer (EET) chains is associated with a tremendous decrease in electron transfer rates. As the acquired electron transfer rates were not competitive to <i>S. oneidensis</i>, it was hypothesized that protein localization and maturation might be affected by heterologous expression. Hence, the type II secretion system from <i>S. oneidensis</i> was also transplanted into an <i>E. coli</i> strain. The latter allowed the secretion of the terminal reductase MtrC onto the cell surface of <i>E. coli</i> for the first time. This was correlated with significantly increased but still insufficient extracellular electron transfer rates. Further experiments suggest that the correct folding of MtrB might be a further bottleneck.IMPORTANCEResearch on transplanting extracellular electron transfer (EET) chains into non-native exoelectrogens is vital for advancing bioenergy and bioremediation technologies. Enabling these organisms to transfer electrons to external surfaces like anodes can enhance microbial fuel cell efficiency and electricity generation from organic waste. This approach can broaden the range of substrates and products for biotechnological applications, offering innovative solutions for sustainable production. Our work shows that transplanting the EET chain of <i>Shewanella oneidensis</i> into <i>Escherichia coli</i> is more complex than previously suggested. The heterologous expression of only <i>c</i>-type cytochromes and the β-barrel protein MtrB is insufficient for competitive reduction rates. Predominantly, MtrC and MtrB require specific proteins for transport and folding, necessitating co-expression and maturation. We could identify the type II secretion system of <i>S. oneidensis</i> as crucial for MtrC secretion in <i>E. coli</i>. Thereby, this work highlights the substrate specificity of bacterial type II secretion systems, suggesting methods to optimize protein production and secretion in bioelectrochemical applications.</p>","PeriodicalId":8002,"journal":{"name":"Applied and Environmental Microbiology","volume":" ","pages":"e0068525"},"PeriodicalIF":3.9,"publicationDate":"2025-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143958061","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":"Impact of flushing procedures on drinking water biostability and invasion susceptibility in distribution systems.","authors":"Fien Waegenaar, Thomas Pluym, Elise Vermeulen, Bart De Gusseme, Nico Boon","doi":"10.1128/aem.00686-25","DOIUrl":"https://doi.org/10.1128/aem.00686-25","url":null,"abstract":"<p><p>Ensuring high-quality drinking water remains challenging, as complaints about odors, discoloration, or contamination persist. In Belgium and beyond, traditional flushing is a common curative strategy that involves discharging large water volumes through hydrants while the network remains in use. In some cases, free chlorine (0.5 mg/L) is added, and consumers are advised not to drink the water. However, flushing can alter water biostability, potentially increasing susceptibility to microbial invasion. This study used a pilot-scale drinking water distribution system with three identical 100 m polyvinyl chloride(PVC) loops (DN 80 mm) to assess the impact of flushing with and without chlorination as practiced in chlorinated networks. Loop 1 was flushed with tap water and sodium hypochlorite (NaOCl), followed by two non-chlorinated flushes, loop 2 was unflushed, and loop 3 underwent three flushes. Biostability was assessed using online flow cytometry, and susceptibility to bacterial invasion (<i>Aeromonas media</i>, <i>Pseudomonas putida</i>, and <i>Serratia fonticola</i>) was evaluated in the days following flushing. The water had a 7-day residence time. Results showed that chlorinated flushing promoted microbial regrowth (3.8 × 10⁵ vs 2.0 × 10⁵ and 1.6 × 10⁵ cells/mL for loops 1, 2, and 3, respectively), primarily of resident <i>Sphingopyxis</i> spp. Biofilm cell densities (~4 × 10⁶ cells/cm²) remained stable across conditions. Bacterial indicators declined over time, with <i>P. pudita</i> and <i>S. fonticola</i> surviving longer (>100 hours) than <i>A. media</i> (13 hours). Decay rates were highest in chlorinated loops, likely due to increased microbial competition. For example, the decay constant of <i>S. fonticola</i> at 20°C was -0.082 h^-1, -0.042 h^-1, and -0.027 h^-1 for loops 1, 2, and 3, respectively.</p><p><strong>Importance: </strong>Traditional flushing is used as a curative strategy to solve unwanted quality issues during distribution, yet its impact on microbial biostability remains poorly understood. This study provides critical insights into how traditional flushing, both with and without chlorination, influences microbial regrowth and susceptibility to invasion. Findings reveal that chlorinated flushing promotes the regrowth of resident drinking water bacteria while accelerating the decay of introduced unwanted bacterial indicators, emphasizing the complex trade-off between microbial control and system stability. Understanding these dynamics is essential for optimizing flushing procedures, minimizing unintended consequences, and improving distribution system resilience.</p>","PeriodicalId":8002,"journal":{"name":"Applied and Environmental Microbiology","volume":" ","pages":"e0068625"},"PeriodicalIF":3.9,"publicationDate":"2025-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143966500","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":"Marked reduction of SARS-CoV-2 infection and improved recovery following supplementation with a probiotic mix of four strains and two strains of <i>Bifidobacterium breve</i> in hamsters.","authors":"Edgar Torres-Maravilla, Marine Wasniewski, Aurélie Wauquier, Alexandre Servat, Evelyne Picard-Meyer, Elodie Monchatre-Leroy, Sandrine Auger, Sophie Holowacz, Franck Boué, Philippe Langella, Elsa Jacouton, Anne-Judith Waligora-Dupriet","doi":"10.1128/aem.00648-25","DOIUrl":"https://doi.org/10.1128/aem.00648-25","url":null,"abstract":"<p><p>Only a few studies have shown that certain probiotics have beneficial effects on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. In this study, two strains of <i>Bifidobacterium breve</i>, CNCM I-5644 and CNCM I-5979, selected for their <i>in vitro</i> immunomodulatory properties demonstrated in a screening of 20 strains and a mixture of 4 probiotic strains selected based on its immunomodulatory and antiviral properties were evaluated in a hamster model of SARS-CoV-2 infection. Supplementation with these probiotics (7 days before plus 7 days after infection) reduced SARS-CoV-2 infection with a significantly reduced viral load in the upper respiratory tract and lungs and improved weight recovery. Probiotics also counteracted the increase in inflammatory markers and intestinal permeability. The impact of these probiotics was independent of microbiota composition and short-chain fatty acid production. Overall, these data suggest that the probiotics tested, in particular the mix containing <i>Bifidobacterium longum</i> LA101, <i>Lactobacillus helveticus</i> LA102, <i>Lactococcus lactis</i> LA103, and <i>Streptococcus thermophilus</i> LA104, can facilitate recovery from SARS-CoV-2 infection (as shown by weight regain in infected hamsters) by reducing viral load and inflammation.</p><p><strong>Importance: </strong>Our study investigated the potential benefits of specific probiotics in fighting severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection (COVID-19). We tested two strains of <i>Bifidobacterium breve</i> selected based on their immune-boosting properties, along with a commercial mix of four probiotic strains chosen for its antiviral and immune-modulating effects. These probiotics were administered to hamsters over a week before and a week after infection. Supplementation with these probiotics significantly reduced the viral load in the upper respiratory tract and lungs, promoting recovery as demonstrated by the weight regain observed. In addition to reducing viral presence, the probiotics also helped lower inflammation and improved gut health by counteracting increased intestinal permeability. Our findings suggest that probiotics, particularly the mix of four strains, could support recovery from SARS-CoV-2 infection by reducing inflammation, viral load, and enhancing overall health.</p>","PeriodicalId":8002,"journal":{"name":"Applied and Environmental Microbiology","volume":" ","pages":"e0064825"},"PeriodicalIF":3.9,"publicationDate":"2025-05-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143969199","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":"Mobilizable shuttle vectors with fluorescent markers functional across different species of bacteria.","authors":"Zackary R Armstrong, Janie Alonso, Venus Stanton, Nikhil Patel, Xhavit Zogaj, Sebastian S Cocioba, Karl E Klose","doi":"10.1128/aem.00045-25","DOIUrl":"https://doi.org/10.1128/aem.00045-25","url":null,"abstract":"<p><p>Chromophore-containing proteins (CCPs), including fluorescent and non-fluorescent (chromoproteins), have been widely used in microbiological research. However, several roadblocks often limit their use in non-model bacterial species, including efficient transformation, suitable plasmid origins of replication, and optimal promoter choice. Here, we have engineered a set of 32 shuttle plasmids designed to overcome these roadblocks in an effort to streamline this process for future research. We have selected eight different CCPs: eforCP, YukonOFP, DasherGFP, tinsel Purple, aeBlue, FuGFP, super-folder GFP, and super-folder Cherry2. To broaden the potential host range, we utilized two distinct backbones with p15a either fused to a <i>Francisella</i> origin (FnOri) or to the broad host origin RSF1010 and included a transfer origin (<i>oriT</i>) to facilitate transformation via conjugation. Moreover, we have created versions of each vector, which confer resistance to either kanamycin or chloramphenicol. Lastly, to enable promoter-swapping, we engineered the constitutive p<i>J23100</i> promoter element to be flanked by <i>BsaI</i> sites, thereby enabling promoter exchange by the Golden Gate assembly to evaluate CCP expression with different host promoters. To demonstrate the usability of the pKEK-Chrom plasmid series, we evaluated their expression in <i>Escherichia coli</i>, <i>Shewanella oneidensis</i>, and <i>Vibrio alginolyticus</i>. We further demonstrated the utility of promoter swapping in <i>Francisella novicida</i> and validated the functionality of the RSF1010 origin in <i>Acinetobacter baumannii</i>. In summary, the pKEK-Chrom plasmid series provides a palette of different CCPs that streamline their use in non-model gram-negative bacteria.</p><p><strong>Importance: </strong>Chromophore-containing proteins (CCPs), including both fluorescent proteins and pigment-producing (non-fluorescent) chromoproteins, have become invaluable tools for microbial research. However, their successful implementation in understudied bacterial species lacking established genetic tools often requires substantial time and resources. Our goal was to develop a set of plasmid-based vectors that could streamline CCP expression in gram-negative bacteria. To do so, we developed a set of 32 plasmid vectors, the pKEK-Chrom plasmid series, specifically designed to facilitate CCP expression across different bacteria, including <i>Escherichia coli</i>, <i>Vibrio alginolyticus</i>, <i>Shewanella oneidensis</i>, <i>Francisella novicida</i>, and <i>Acinetobacter baumannii</i>.</p>","PeriodicalId":8002,"journal":{"name":"Applied and Environmental Microbiology","volume":" ","pages":"e0004525"},"PeriodicalIF":3.9,"publicationDate":"2025-05-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143972736","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":"Ecological mechanisms of microbial assembly in clonal plant <i>Glechoma longituba</i>: from soil to endosphere.","authors":"Yunshi Li, Na Qu, Shuang Li, Huaizhe Zhou, Ming Yue","doi":"10.1128/aem.00336-25","DOIUrl":"https://doi.org/10.1128/aem.00336-25","url":null,"abstract":"<p><p>Climate change presents significant challenges to plant growth and reproduction. Clonal plants, with low genetic diversity, are particularly vulnerable due to their limited adaptive capacity. Plant-associated microbiomes can play a crucial role in enhancing clonal plant survival and adaptability, yet the mechanisms governing microbial community assembly along the soil-episphere-endosphere continuum remain unclear. In this study, we investigated microbial community assembly patterns in the clonal plant <i>Glechoma longituba</i>. Our findings demonstrate that the assembly of microbial communities is primarily driven by host-related factors rather than external environmental filtering. First, host selection reduced α-diversity and network complexity while increasing β-diversity and community stability. Second, the mechanisms of microbial assembly transitioned from stochastic dominance in bulk soil and epiphytic compartments to deterministic processes within endophytic niches. Third, the taxonomic structure exhibited significant turnover along the soil-episphere-endosphere continuum, accompanied by functional redundancy to maintain ecosystem functions. The results support the hypothesis that host selection optimizes the functional composition of microbial communities by reducing diversity and network complexity while ensuring the stability of key functional microorganisms. The study emphasizes the critical role of host-microbe interactions in sustaining the adaptive and functional advantages of clonal plants, offering insights into managing sustainable plant communities under climate change.IMPORTANCEThis study highlights the vital role of plant-associated microbiomes in helping clonal plants, which have low genetic diversity, adapt to climate change. By examining the clonal plant <i>Glechoma longituba</i>, the research reveals that the plant itself plays a key role in shaping its microbial communities, rather than external environmental factors. Host selection simplifies microbial diversity and network complexity but enhances community stability and functional efficiency. These findings suggest that clonal plants can optimize their microbiomes to maintain critical functions. This work provides valuable insights into how plants and microbes interact to improve resilience, offering potential strategies for managing plant communities in a changing climate. By understanding these mechanisms, we can better support sustainable ecosystems and agricultural practices in the face of global environmental challenges.</p>","PeriodicalId":8002,"journal":{"name":"Applied and Environmental Microbiology","volume":" ","pages":"e0033625"},"PeriodicalIF":3.9,"publicationDate":"2025-05-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143953920","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":"Application of exogenous electron mediator in fermentation to enhance the production of value-added products.","authors":"Yingxuan Yu, Zhongliang Shi, Weiming Li, Mengyang Bian, Chi Cheng, Yimei Xi, Shuhua Yao, Xiangfeng Zeng, Yongfeng Jia","doi":"10.1128/aem.00495-25","DOIUrl":"https://doi.org/10.1128/aem.00495-25","url":null,"abstract":"<p><p>Electron transfer is essential for the production efficiency of value-added products in anaerobic fermentation, such as butanol and ethanol as biofuels, and short-chain fatty acids (SCFAs) including butyric acid and acetic acid as platform chemicals. Electron mediators (EMs), also known as electron shuttles, can facilitate electron transfer to counter irreversible or slow redox reactions that limit fermentation. The addition of EMs has been shown to be an effective strategy to promote fermentation by various bacteria, particularly <i>Clostridium</i> species, for these valuable product syntheses. This paper reviews recent advancements in the application of exogenous electron mediators (EEMs) across various scenarios. Common EEM types, their characteristics, and mechanisms are summarized, and different application scenarios are discussed to elucidate the effect of EEMs. Key technical challenges and future directions for EEM application are also explored.</p>","PeriodicalId":8002,"journal":{"name":"Applied and Environmental Microbiology","volume":" ","pages":"e0049525"},"PeriodicalIF":3.9,"publicationDate":"2025-05-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143973574","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 cell-cell communication signal from <i>Enterobacter cloacae</i> interfering with the signaling systems and virulence in <i>Shigella sonnei</i>.","authors":"Xiayu Chen, Mingfang Wang, Zhuoxian Zhao, Xiwen Ling, Ganjin Peng, Binbin Cui, Qiaoping Wang, Bing Gu, Yinyue Deng","doi":"10.1128/aem.00510-25","DOIUrl":"https://doi.org/10.1128/aem.00510-25","url":null,"abstract":"<p><p>Quorum sensing (QS) is widely utilized by both bacteria and fungi to mediate cell-cell communication. Previous studies have demonstrated that the indole derivative indole-3-ethanol (also known as tryptophol) controls morphogenesis as a QS molecule in fungi. However, whether this QS signal is involved in the modulation of biological functions in bacteria remains unknown. Here, we report that indole-3-ethanol controls the biological functions and pathogenicity of <i>Enterobacter cloacae</i> subsp. <i>cloacae</i> ATCC 13047. The biosynthesis of indole-3-ethanol is performed by YjgB (ECL_RS22935), an alcohol dehydrogenase. Deletion of <i>yjgB</i> results in impaired biological functions and virulence. Furthermore, we revealed that indole-3-ethanol from <i>E. cloacae</i> reduces the competitive fitness of <i>Shigella sonnei</i> by inhibiting its biofilm formation, extracellular polysaccharide synthesis, and virulence. Given that both <i>E. cloacae</i> and <i>S. sonnei</i> are common human intestinal microbes, our results highlight the critical roles of indole-3-ethanol in both intraspecies signaling and interspecies communication in bacteria.</p><p><strong>Importance: </strong>Quorum sensing is a cell-cell communication mechanism widely employed by bacteria to control various biological functions and pathogenicity. In this study, we demonstrated that <i>Enterobacter cloacae</i> employs indole-3-ethanol as a quorum-sensing signal to control biological functions and virulence. We also revealed that indole-3-ethanol from <i>E. cloacae</i> effectively inhibits biofilm formation and virulence in <i>Shigella sonnei</i>. Our findings not only suggest the important role of indole-3-ethanol in the regulation of the pathogenicity of <i>E. cloacae</i> but also provide new insights into the development of indole-3-ethanol as an anti-virulence agent against <i>S. sonnei</i>.</p>","PeriodicalId":8002,"journal":{"name":"Applied and Environmental Microbiology","volume":" ","pages":"e0051025"},"PeriodicalIF":3.9,"publicationDate":"2025-05-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143963200","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":"7β-Hydroxysteroid dehydratase Hsh3 eliminates the 7-hydroxy group of the bile salt ursodeoxycholate during degradation by <i>Sphingobium</i> sp. strain Chol11 and other <i>Sphingomonadaceae</i>.","authors":"Phil Richtsmeier, Ruslan Nedielkov, Malte Haring, Onur Yücel, Lea Elsner, Rebekka Herdis Lülf, Lars Wöhlbrand, Ralf Rabus, Heiko Moeller, Bodo Philipp, Franziska Maria Mueller","doi":"10.1128/aem.00185-25","DOIUrl":"https://doi.org/10.1128/aem.00185-25","url":null,"abstract":"<p><p>Bile salts are steroids with distinctive hydroxylation patterns that are produced and excreted by vertebrates. In contrast to common human bile salts, ursodeoxycholate (UDCA) has a 7-hydroxy group in β-configuration and is used in large amounts for the treatment of diverse gastrointestinal diseases. We isolated the 7β-hydroxysteroid dehydratase Hsh3 that is involved in UDCA degradation by <i>Sphingobium</i> sp. strain Chol11. Hsh3 eliminates the 7β-hydroxy group as water, leading to a double bond in the B-ring. This is similar to 7α-hydroxysteroid dehydratases in this and other strains, but Hsh3 is evolutionarily different from these. Purified Hsh3 accepted steroids with and without side chains as substrates and had minor activity with 7α-hydroxy groups. The deletion mutant strain Chol11 Δ<i>hsh3</i> had impacted growth with UDCA and accumulated a novel compound. The compound was identified as 3',5-dihydroxy-H-methyl-hexahydro-5-indene-1-one-propanoate, consisting of steroid rings C and D with a C₃-side chain carrying the former 7β-hydroxy group, indicating that Hsh3 activity is important especially for the later stages of bile salt degradation. Hsh3 homologs were found in other sphingomonads that were also able to degrade UDCA as well as in environmental metagenomes. Thus, Hsh3 adds to the bacterial enzyme repertoire for degrading a variety of differently hydroxylated bile salts.IMPORTANCEThe bacterial degradation of different bile salts is not only important for the removal of these steroidal compounds from the environment but also harbors interesting enzymes for steroid biotechnology. The 7β-hydroxy bile salt ursodeoxycholate (UDCA) naturally occurs in high concentration in the feces of black bears and has important pharmaceutical relevance for the treatment of different liver-related diseases, for which it is administered in high and increasing amounts. Additionally, it is present in the bile salt pool of humans in trace amounts. While UDCA degradation is environmentally important, the enzyme Hsh3 modifies the hydroxy group that confers the medically relevant properties and thus might be interesting for microbiome analyses and biotechnological applications.</p>","PeriodicalId":8002,"journal":{"name":"Applied and Environmental Microbiology","volume":" ","pages":"e0018525"},"PeriodicalIF":3.9,"publicationDate":"2025-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144060932","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":"Molecular adaptations specific to extreme halophilic archaea could promote high perchlorate tolerance.","authors":"Jorge Díaz-Rullo, José Eduardo González-Pastor","doi":"10.1128/aem.00512-25","DOIUrl":"https://doi.org/10.1128/aem.00512-25","url":null,"abstract":"<p><p>Perchlorate is a strong chaotropic agent that causes macromolecule denaturation, DNA damage, and oxidative stress. However, perchlorate deliquescence is thought to promote the formation of liquid salt brines, even at hyper-arid and cold environments, such as the Martian regolith. For that reason, the detection of high levels of perchlorate at different locations on the Martian surface led to hypotheses about the existence of Martian microenvironments compatible with life, especially with those organisms tolerant to hyper-salinity and perchlorate. Extreme halophilic archaea have been proposed as the best candidates to inhabit those environments not only due to their high tolerance to salinity and perchlorate, but also because of their resistance to a wide variety of stress conditions. Since specific perchlorate responses remain largely unknown, in this work, we have analyzed the molecular mechanisms of perchlorate tolerance exhibited by the model extreme halophilic archaeon <i>Haloferax volcanii</i> using a transcriptomic approach. We report that perchlorate produced transcriptional effects opposite to those of salinity, and we propose that the \"salt-in\" strategy could promote high perchlorate tolerance in extreme halophilic archaea due to the intracellular accumulation of KCl, which may shield the chaotropic activity of perchlorate. This natural adaptation would be enhanced by changes in other stress responses like DNA repair, refolding and turnover of damaged proteins, removal of oxidative species, and tRNA modifications, among others. These results may help to understand how life could survive on Mars, now or in the past, and highlight the importance of extreme halophiles in the development of <i>in situ</i> resource utilization systems.IMPORTANCEPerchlorate is a toxic chlorinated compound that promotes the formation of liquid salt brines, even at hyper-arid and cold environments. For the past two decades, different probes have reported high levels of perchlorate salts at multiple locations on the Martian surface, which could facilitate the presence of potentially habitable environments by specific microorganisms capable of tolerating both hyper-salinity and high perchlorate concentrations. Therefore, the significance of this research was to investigate the molecular mechanisms for perchlorate tolerance using the extreme haloarchaeon <i>Haloferax volcanii</i> as a model organism. This analysis leads to the identification of critical genes and pathways involved in perchlorate tolerance and supports that certain molecular adaptations specific to extreme haloarchaea may be responsible for the high levels of perchlorate tolerance exhibited by these microorganisms, serving as a valuable resource for Mars exploration.</p>","PeriodicalId":8002,"journal":{"name":"Applied and Environmental Microbiology","volume":" ","pages":"e0051225"},"PeriodicalIF":3.9,"publicationDate":"2025-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143966501","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}