Applied and Environmental Microbiology最新文献

{"title":"Optimizing experimental conditions: the role of buffered environments in microbial isolation, physiological studies, and taxonomic characterization.","authors":"Om Prakash, Ujjwala Waghmare, Ashvini Chauhan, Yogesh Patil","doi":"10.1128/aem.01728-24","DOIUrl":"10.1128/aem.01728-24","url":null,"abstract":"<p><p>Using a buffered medium is considered essential for enriching and cultivating novel microbial taxa, studying their pH range and optima, and conducting different physiological experiments. Experimental evidence showed that different buffer compounds impact microbial physiology and cell growth differently, and some of them exert toxic and inhibitory effects on organisms under study. Laboratory growth media supplemented with incompatible buffers could also suppress the organism's growth. Therefore, the selection of buffers without the knowledge of their implications on cell growth and physiology in such experiments yields an inaccurate estimate of their physiological abilities and pH range and optima. In this paper, the authors argue against the use of buffered medium to enrich and isolate novel taxa and suggest determining the pH range and optima using unbuffered medium for taxonomic description and physiological characterization. Based on previous literature and our observations, we recommend the use of rich universal laboratory growth medium with their pH adjusted using 1 N NaOH and/or 1 N HCl for such studies, except in cases where the organism cannot grow in such media. However, the pH of the growth medium must be continuously monitored, and in cases where the medium's buffering capacity is compromised, a suitable pH buffer with only a neutral effect on cell growth must be used for more accurate physiological experiments with that organism in the future. Based on the inhibitory effects of buffers on different cells (prokaryotes and eukaryotes) and physiological activities, in this manuscript, we also recommend that the compatibility of the buffers should be first screened before starting any physiological experiments, and any buffer compound should be avoided in the culture medium during the designing of the culturomics protocols for the cultivation of novel taxa from natural samples.</p>","PeriodicalId":8002,"journal":{"name":"Applied and Environmental Microbiology","volume":" ","pages":"e0172824"},"PeriodicalIF":3.9,"publicationDate":"2025-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12175527/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143957399","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","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":"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":"2025-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12175533/pdf/","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":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Analysis of the SARS-CoV-2 inactivation mechanism using violet-blue light (405 nm).","authors":"Davide Amodeo, Serena Marchi, Lia Fiaschi, Luisa Raucci, Camilla Biba, Valentina Salvestroni, Claudia Maria Trombetta, Ilaria Manini, Maurizio Zazzi, Emanuele Montomoli, Ilaria Vicenti, Gabriele Cevenini, Gabriele Messina","doi":"10.1128/aem.00403-25","DOIUrl":"10.1128/aem.00403-25","url":null,"abstract":"<p><p>The study evaluated the effects of violet-blue light (VBL) on cell viability and replication, carbonylation of three structural proteins (S, E, and N) and one non-structural protein (NSP13), and direct damage to the RNA of SARS-CoV-2. The virus was exposed to increasing doses of VBL along with influenza A and B viruses to compare their susceptibility. At the highest dose (21.6 J/cm²), SARS-CoV-2 was significantly more susceptible to VBL than the influenza viruses, with a reduction in viral titer of 2.33 log₁₀. Viral RNA did not show significant changes after exposure to VBL, as demonstrated by next-generation sequencing and real-time PCR quantification, suggesting that the inactivation process does not involve direct nucleic acid damage. To exclude the role of the culture suspension in the inactivation process, virus viability experiments were performed using different dilutions of Dulbecco's modified Eagle's medium (DMEM) in phosphate-buffered saline (PBS). The results indicated that the suspension medium played a secondary role in virus inactivation, as viability did not increase with increasing DMEM dilution. Subsequent tests with three different antioxidants (NAC, AsA, and SOD) at different concentrations prevented viral inactivation, from 99.99% to 85.43% (with SOD 0.003 mM). Carbonylation of S and E proteins was more pronounced when viruses were suspended in DMEM rather than PBS, although the tests demonstrated that the intrinsic properties of the viral membrane were a crucial element to consider in relation to its susceptibility to VBL.IMPORTANCELight-based disinfection methods are often used in combination with other cleaning methods due to their non-invasive nature, versatility, and environmental benefits. VBL is an effective approach as it induces the production of reactive oxygen species that reduce microbial viability. In this study, lipid peroxidation was identified as an important factor affecting the structural integrity and function of the viral envelope, reducing its ability to interact with host cells and consequently its ability to be infectious. The lipid envelope of SARS-CoV-2, composed mainly of glycerophospholipids and lacking cholesterol and sphingolipids, appears to be the critical factor in its susceptibility, distinguishing it from influenza viruses, which have a lipid profile richer in components that protect against oxidative stress.</p>","PeriodicalId":8002,"journal":{"name":"Applied and Environmental Microbiology","volume":" ","pages":"e0040325"},"PeriodicalIF":3.9,"publicationDate":"2025-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12175510/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143972815","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","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":"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":"2025-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12175503/pdf/","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":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Replacement of branched-chain polyamine biosynthesis with thermospermine supports survival under both cold and heat stress in the hyperthermophilic archaeon <i>Thermococcus kodakarensis</i>.","authors":"Shinsuke Fujiwara, Riko Satake, Himari Aoki, Kaho Yamada, Yuri Ishii, Wakao Fukuda","doi":"10.1128/aem.00326-25","DOIUrl":"10.1128/aem.00326-25","url":null,"abstract":"&lt;p&gt;&lt;p&gt;&lt;i&gt;N&lt;sup&gt;4&lt;/sup&gt;&lt;/i&gt;-bis(aminopropyl)spermidine (BCPA), a branched-chain polyamine, is uniquely found in bacterial and archaeal hyperthermophiles. In &lt;i&gt;Thermococcus kodakarensis&lt;/i&gt;, BCPA is synthesized by BCPA synthase (BpsA), an aminopropyl transferase encoded by &lt;i&gt;bpsA&lt;/i&gt;. This highly positively charged molecule is localized in both the nucleic acid and membrane fractions of &lt;i&gt;T. kodakarensis&lt;/i&gt; cells. The &lt;i&gt;bpsA&lt;/i&gt; deletion strain (DBP1), which lacks BCPA, failed to grow at 93°C and exhibited poor survival under repeated cold stress, indicating that BCPA is essential for membrane stability and function &lt;i&gt;in vivo&lt;/i&gt;. Additionally, the expression of specific genes, including the cytoplasmic hydrogenase subunit &lt;i&gt;hyhL&lt;/i&gt;, was absent in DBP1, suggesting a role for BCPA in gene regulation. To further investigate BCPA's function, we replaced &lt;i&gt;bpsA&lt;/i&gt; in &lt;i&gt;T. kodakarensis&lt;/i&gt; with &lt;i&gt;speE&lt;/i&gt; from the hyperthermophilic archaeon &lt;i&gt;Pyrobaculum calidifontis&lt;/i&gt;, enabling the production of norspermine instead of BCPA. The resulting KPS strain accumulated thermospermine as its major polyamine. Growth at 93°C was partially restored in KPS, and cold-stress survival improved significantly. Additionally, KPS exhibited biosurfactant (sophorolipid) tolerance comparable to that of the parental &lt;i&gt;T. kodakarensis&lt;/i&gt; strain KU216 under thermal conditions. Furthermore, &lt;i&gt;hyhL&lt;/i&gt; expression was restored in KPS, as confirmed by immunoblotting with anti-HyhL antisera, suggesting that thermospermine can functionally compensate for BCPA. Notably, mutant DBP1 cells lacking both BCPA and thermospermine did not survive repeated cycles of cold and heat stress. This observation suggests that these polyamines play a crucial role in long-term survival, potentially facilitating hibernation-like states in natural environments where extreme temperature fluctuations occur.IMPORTANCEAt the hot springs of Kodakarajima Island, surrounded by cold ocean water, diverse hyperthermophiles, including &lt;i&gt;Thermococcus, Thermotoga,&lt;/i&gt; and &lt;i&gt;Thermus&lt;/i&gt; species, naturally produce branched-chain polyamines (BCPAs) via a unique aminopropyltransferase BpsA, in addition to spermidine. In &lt;i&gt;Pyrobaculum calidifontis&lt;/i&gt;, the &lt;i&gt;Pc-&lt;/i&gt;SpeE enzyme produces norspermine &lt;i&gt;in vivo&lt;/i&gt;. However, when the &lt;i&gt;speE&lt;/i&gt; gene from &lt;i&gt;P. calidifontis&lt;/i&gt; is introduced into &lt;i&gt;Thermococcus kodakarensis&lt;/i&gt;, the transformant (Δ&lt;i&gt;bpsA::Pc-speE&lt;/i&gt;) produces thermospermine instead of norspermine. This shift suggests that the product specificity of &lt;i&gt;Pc-&lt;/i&gt;SpeE is influenced by factors inherent to the host organism. Interestingly, thermospermine appears to functionally substitute for BCPA, potentially by forming BCPA-like structures with bent nitrogen atoms. This structural mimicry could contribute to cellular stability under both heat and cold stress, highlighting a potential mechanism for temperature and stress adaptation in &lt;i&gt;T. kodakarensis&lt;/i&gt;. These findings further suggest t","PeriodicalId":8002,"journal":{"name":"Applied and Environmental Microbiology","volume":" ","pages":"e0032625"},"PeriodicalIF":3.9,"publicationDate":"2025-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12175538/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144155885","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Experimental assessment of interactions between marine bacteria and model protists: from predator-prey relationships to bacterial-mediated lysis.","authors":"Diana Axelsson-Olsson, Nikolaj Gubonin, Stina Israelsson, Jarone Pinhassi","doi":"10.1128/aem.00929-25","DOIUrl":"10.1128/aem.00929-25","url":null,"abstract":"<p><p>Bacteria in aquatic environments are a principal food source for predatory protists. Whereas interactions between bacteria and protists are recognized to determine the pathogenesis and epidemiology of several human pathogens, few studies have systematically characterized the interactions between specific aquatic bacteria and protists beyond the prey-predator relation. We, therefore, surveyed individual co-cultures between 18 different genome-sequenced marine bacteria with known virulence gene repertoires and three model protist species widely used for assessing bacteria-protist interactions. Strikingly, 10, 5, and 3 bacterial isolates were capable of lysing the protists <i>Acanthamoeba polyphaga, Tetrahymena pyriformis,</i> and <i>Euglena gracilis</i>, respectively. A majority of the bacteria were able to grow and/or maintain viable populations in the presence of viable protists. Some bacteria survived longer with viable protists but not heat-killed protists and were observed in protist vacuoles. In this respect, marine bacteria are similar to several protist-dependent human pathogens, including <i>Legionella</i>. Analyses of growth patterns in low-nutrient media showed that co-cultivation with <i>A. polyphaga</i> allowed one bacterial strain to overcome nutritional stress and obtain active growth. Five isolates depended on viable amoebae to grow, notwithstanding nutrient media status. The remarkable capability of these marine bacteria to survive encounters with, and even actively kill, model predatory protists under laboratory conditions suggests that diverse bacterial defense strategies and virulence mechanisms to access nutrients may be important in shaping microbial interactions. If verified with native marine and freshwater populations, the diversity of interactions uncovered here has implications for understanding ecological and evolutionary consequences of population dynamics in bacteria and protists.IMPORTANCEThe microbiome constitutes the base of food webs in aquatic environments. Its composition partly reflects biotic interactions, where bacteria primarily are considered prey of predatory protists. However, studies that focus on one or a few species have shown that some bacteria have abilities to escape grazing and may even be capable of lysing their protist predators. In this study, we substantially extend these findings by systematically investigating interactions among multiple taxa of both bacteria and protists. Our results show that marine bacteria display a wider and more complex range of interactions with their predators than generally recognized-from growth dependency to protist lysis. Given that such interactions play key roles in the pathogenesis and epidemiology of several human pathogens, our findings imply that bacterial virulence traits can contribute to defining the structure and ecology of aquatic microbiomes.</p>","PeriodicalId":8002,"journal":{"name":"Applied and Environmental Microbiology","volume":" ","pages":"e0092925"},"PeriodicalIF":3.9,"publicationDate":"2025-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12175539/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144186334","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The APSES transcription factor Swi6B upregulates <i>CATALASE 1</i> transcription to enhance oxidative stress tolerance of <i>Ganoderma lucidum</i>.","authors":"Lingshuai Wang, Lingyan Shi, Shuhan Zhang, Jiping Ma, Cheng Zhang, Huhui Chen, Mingwen Zhao","doi":"10.1128/aem.00679-25","DOIUrl":"https://doi.org/10.1128/aem.00679-25","url":null,"abstract":"<p><p>As sessile organisms, fungi often encounter various stresses throughout their lifespan, resulting in the overproduction of reactive oxygen species, which impedes the normal growth of fungi. Previously, we revealed that the Swi6B transcription factor is involved in the stress tolerance of <i>Ganoderma lucidum</i>. However, the underlying molecular mechanism is unclear. The present study demonstrated that oxidative stress increased the levels of Swi6B. Direct binding of Swi6B to the promoter region of <i>catalase 1</i> (<i>CAT1</i>) resulted in increased transcription of <i>CAT1</i> and reduced H₂O₂ levels in <i>SWI6B</i> overexpressing strains. In addition to increased Swi6B protein, the phosphorylation level of Swi6B was increased by H₂O₂ treatment. The overexpression of <i>SLT2</i>, a mitogen-activated protein kinase that interacts with Swi6B, increased the phosphorylation level of Swi6B, and treatment with H₂O₂ further enhanced this increase. As a result, both the binding of Swi6B to the <i>CAT1</i> gene and tolerance to H₂O₂ were increased in <i>SLT2</i>-overexpressing strains. The present findings revealed that the Slt2-Swi6B-CAT1 pathway responds to oxidative stress and contributes to improving the survival of <i>G. lucidum</i> in adverse environments.IMPORTANCEIn fungi, environmental stress leads to the accumulation of intracellular reactive oxygen species and leads to oxidative stress. Here, we found that the overexpression of the APSES transcription factor <i>Swi6B</i> enhances tolerance to oxidative stress in <i>Ganoderma lucidum</i>. Swi6B binds to the promoter region of <i>CAT1</i>, which increases <i>CAT1</i> transcription and reduces the H₂O₂ levels. In addition, the phosphorylation of Swi6B by Slt2 promotes the regulation of <i>CAT1</i> by Swi6B. The Slt2-Swi6B-CAT1 pathway is important for the response of <i>G. lucidum</i> to oxidative stress.</p>","PeriodicalId":8002,"journal":{"name":"Applied and Environmental Microbiology","volume":" ","pages":"e0067925"},"PeriodicalIF":3.9,"publicationDate":"2025-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144324326","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":"Articles of Significant Interest in This Issue.","authors":"","doi":"10.1128/aem.01148-25","DOIUrl":"10.1128/aem.01148-25","url":null,"abstract":"","PeriodicalId":8002,"journal":{"name":"Applied and Environmental Microbiology","volume":"91 6","pages":"e0114825"},"PeriodicalIF":3.9,"publicationDate":"2025-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12180515/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144324327","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Toward simulating offshore oilfield conditions: insights into microbiologically influenced corrosion from a dual anaerobic biofilm reactor.","authors":"Liam M Jones, Niall Hanrahan, Maria Salta, Torben Lund Skovhus, Kathryn Thomas, Timothy Illson, Julian Wharton, Jeremy S Webb","doi":"10.1128/aem.02221-24","DOIUrl":"10.1128/aem.02221-24","url":null,"abstract":"<p><p>Oilfield systems are a multifaceted ecological niche, which consistently experiences microbiologically influenced corrosion. However, simulating the environmental conditions of an offshore system within the laboratory is notoriously difficult. A novel dual anaerobic biofilm reactor protocol allowed a complex mixed-species marine biofilm to be studied. Interestingly, electroactive corrosive bacteria and fermentative electroactive bacteria growth was supported within the biofilm microenvironment. Critically, the biotic condition exhibited pits with a greater average area, which is characteristic of microbiologically influenced corrosion. This research seeks to bridge the gap between experimental and real-world scenarios, ultimately enhancing the reliability of biofilm management strategies in the industry.</p><p><strong>Importance: </strong>It is becoming more widely understood that any investigation of microbiologically influenced corrosion requires a multidisciplinary focus on multiple lines of evidence. Although there are numerous standards available to guide specific types of testing, there are none that focus on integrating biofilm testing. By developing a novel dual anaerobic reactor model to study biofilms, insights into the different abiotic and biotic corrosion mechanisms under relevant environmental conditions can be gained. Using multiple lines of evidence to gain a holistic understanding, more sustainable prevention and mitigation strategies can be designed. To our knowledge, this is the first time all these metrics have been combined in one unified approach. The overall aim of this paper was to explore recent advances in biofilm testing and corrosion research and provide recommendations for future standards being drafted. However, it is important to note that this article itself is not intending to serve as a standard.</p>","PeriodicalId":8002,"journal":{"name":"Applied and Environmental Microbiology","volume":" ","pages":"e0222124"},"PeriodicalIF":3.9,"publicationDate":"2025-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12175496/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143539815","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","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":"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":"2025-06-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12175506/pdf/","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":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}