mBio最新文献

{"title":"OXA β-lactamases from <i>Acinetobacter</i> spp. are membrane bound and secreted into outer membrane vesicles.","authors":"Lucia Capodimonte, Fernando Teixeira Pinto Meireles, Guillermo Bahr, Robert A Bonomo, Matteo Dal Peraro, Carolina López, Alejandro J Vila","doi":"10.1128/mbio.03343-24","DOIUrl":"10.1128/mbio.03343-24","url":null,"abstract":"&lt;p&gt;&lt;p&gt;β-lactamases from Gram-negative bacteria are generally regarded as soluble, periplasmic enzymes. NDMs have been exceptionally characterized as lipoproteins anchored to the outer membrane. A bioinformatics study on all sequenced β-lactamases was performed that revealed a predominance of putative lipidated enzymes in the Class D OXAs. Namely, 60% of the OXA Class D enzymes contain a lipobox sequence in their signal peptide, that is expected to trigger lipidation and membrane anchoring. This contrasts with β-lactamases from other classes, which are predicted to be mostly soluble proteins. Almost all (&gt;99%) putative lipidated OXAs are present in &lt;i&gt;Acinetobacter&lt;/i&gt; spp. Importantly, we further demonstrate that OXA-23 and OXA-24/40 are lipidated, membrane-bound proteins in &lt;i&gt;Acinetobacter baumannii&lt;/i&gt;. In contrast, OXA-48 (commonly produced by Enterobacterales) lacks a lipobox and is a soluble protein. Outer membrane vesicles (OMVs) from &lt;i&gt;A. baumannii&lt;/i&gt; cells expressing OXA-23 and OXA-24/40 contain these enzymes in their active form. Moreover, OXA-loaded OMVs were able to protect &lt;i&gt;A. baumannii&lt;/i&gt;, &lt;i&gt;Escherichia coli&lt;/i&gt;, and &lt;i&gt;Pseudomonas aeruginosa&lt;/i&gt; cells susceptible to piperacillin and imipenem. These results permit us to conclude that membrane binding is a bacterial host-specific phenomenon in OXA enzymes. These findings reveal that membrane-bound β-lactamases are more common than expected and support the hypothesis that OMVs loaded with lipidated β-lactamases are vehicles for antimicrobial resistance and its dissemination. This advantage could be crucial in polymicrobial infections, in which &lt;i&gt;Acinetobacter&lt;/i&gt; spp. are usually involved, and underscore the relevance of identifying the cellular localization of lactamases to better understand their physiology and target them.IMPORTANCEβ-lactamases represent the main mechanism of antimicrobial resistance in Gram-negative pathogens. Their catalytic function (cleaving β-lactam antibiotics) occurs in the bacterial periplasm, where they are commonly reported as soluble proteins. A bioinformatic analysis reveals a significant number of putative lipidated β-lactamases, expected to be attached to the outer bacterial membrane. Notably, 60% of Class D OXA β-lactamases (all from &lt;i&gt;Acinetobacter&lt;/i&gt; spp.) are predicted as membrane-anchored proteins. We demonstrate that two clinically relevant carbapenemases, OXA-23 and OXA-24/40, are membrane-bound proteins in &lt;i&gt;A. baumannii&lt;/i&gt;. This cellular localization favors the secretion of these enzymes into outer membrane vesicles that transport them outside the boundaries of the cell. β-lactamase-loaded vesicles can protect populations of antibiotic-susceptible bacteria, enabling them to thrive in the presence of β-lactam antibiotics. The ubiquity of this phenomenon suggests that it may have influenced the dissemination of resistance mediated by &lt;i&gt;Acinetobacter&lt;/i&gt; spp., particularly in polymicrobial infections, being a potent evolutionary adva","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0334324"},"PeriodicalIF":5.1,"publicationDate":"2025-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11796391/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142818505","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"An adenoviral vector encoding an inflammation-inducible antagonist, HMGB1 Box A, as a novel therapeutic approach to inflammatory diseases.","authors":"Kari Ann Shirey, John Joseph, Lynda Coughlan, Haye Nijhuis, Alan W Varley, Jorge C G Blanco, Stefanie N Vogel","doi":"10.1128/mbio.03387-24","DOIUrl":"10.1128/mbio.03387-24","url":null,"abstract":"<p><p>Influenza, as well as other respiratory viruses, can trigger local and systemic inflammation resulting in an overall \"cytokine storm\" that produces serious outcomes such as acute lung injury (ALI) or acute respiratory distress syndrome (ARDS). We hypothesized that gene therapy platforms could be useful in these cases if the production of an anti-inflammatory protein reflects the intensity and duration of the inflammatory condition. The recombinant protein would be produced and released only in the presence of the inciting stimulus, avoiding immunosuppression or other unwanted side effects that may occur when treating infectious diseases with anti-inflammatory drugs. To test this hypothesis, we developed AdV.C3-Tat/HIV-Box A, an inflammation-inducible cassette that remains innocuous in the absence of inflammation but releases HMGB1 Box A, an antagonist of high mobility group box 1 (HMGB1), in response to inflammatory stimuli such as lipopolysaccharide (LPS) or influenza virus infection. We report here that this novel inflammation-inducible HMGB1 Box A construct in a non-replicative adenovirus (AdV) vector mitigates lung and systemic inflammation therapeutically in response to influenza infection. We anticipate that this strategy will apply to the treatment of multiple diseases in which HMGB1-mediated signaling is a central driver of inflammation.IMPORTANCEMany inflammatory diseases are mediated by the action of a host-derived protein, HMGB1, on Toll-like receptor 4 (TLR4) to elicit an inflammatory response. We have engineered a non-replicative AdV vector that produces HMGB1 Box A, an antagonist of HMGB1-induced inflammation, under the control of an endogenous complement component C3 (C3) promoter sequence, that is inducible by LPS and influenza <i>in vitro</i> and <i>ex vivo</i> in macrophages (Mϕ) and protects mice and cotton rats therapeutically against infection with mouse-adapted and human non-adapted influenza strains, respectively, <i>in vivo</i>. We anticipate that this novel strategy will apply to the treatment of multiple infectious and non-infectious diseases in which HMGB1-mediated TLR4 signaling is a central driver of inflammation.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0338724"},"PeriodicalIF":5.1,"publicationDate":"2025-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11796352/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142854709","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Temperate phage-antibiotic synergy is widespread-extending to <i>Pseudomonas</i>-but varies by phage, host strain, and antibiotic pairing.","authors":"Rabia Fatima, Alexander P Hynes","doi":"10.1128/mbio.02559-24","DOIUrl":"10.1128/mbio.02559-24","url":null,"abstract":"<p><p>Bacteriophages (phages) are bacterial-specific viruses that can be used alone or with antibiotics to reduce bacterial load. Most phages are unsuitable for therapy because they are \"temperate\" and can integrate into the host genome, forming a lysogen that is protected from subsequent phage infections. However, integrated phages can be awakened by stressors such as antibiotics. Supported by this interaction, here we explore the potential use of combined temperate phage and antibiotic against the multi-drug-resistant pathogen, <i>Pseudomonas aeruginosa</i>. In all, thirty-nine temperate phages were isolated from clinical strains, and a subset was screened for synergy with six antibiotics (ciprofloxacin, levofloxacin, meropenem, piperacillin, tobramycin, and polymyxin B), using checkerboard assays. Interestingly, our screen identified phages that can synergize with each antibiotic, despite their widely differing targets; however, these are highly phage-antibiotic and phage-host pairing specific. Screening across multiple clinical strains reveals that temperate phages can reduce the antibiotic minimum inhibitory concentration up to 32-fold, even in a resistant isolate, functionally re-sensitizing the bacterium to the antibiotic. Meropenem and tobramycin did not reduce the frequency of lysogens, suggesting a mechanism of action independent of the temperate nature of the phages. By contrast, ciprofloxacin and piperacillin were able to reduce the frequency of lysogeny, the former by inducing phages-as previously reported in <i>E. coli</i>. Curiously, synergy with piperacillin reduced lysogen survivors, but not by inducing the phages, suggesting an alternative mechanism for biasing the phage lysis-lysogeny equilibrium. Overall, our findings indicate that temperate phages can act as adjuvants in clinically relevant pathogens, even in the presence of antibiotic resistance, thereby drastically expanding their therapeutic potential.</p><p><strong>Importance: </strong>The recent discovery that otherwise therapeutically unusable temperate phages can potentiate the activity of antibiotics, resulting in a potent synergy, has only been tested in <i>E. coli</i>, and with a single model phage. Here, working with clinical isolates of <i>Pseudomonas</i> and phages from these isolates, we highlight the broad applicability of this synergy-across a variety of mechanisms but also highlight the limitations of predicting the phage, host, and antibiotic combinations that will synergize.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0255924"},"PeriodicalIF":5.1,"publicationDate":"2025-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11796409/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142864819","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Iron triggers <i>Tv</i>PI4P5K proteostasis and Arf-mediated cell membrane trafficking to regulate PIP₂ signaling crucial for multiple pathogenic activities of the parasitic protozoan <i>Trichomonas vaginalis</i>.","authors":"Kuan-Yi Wu, Yen-Ju Chen, Shu-Fan Lin, Hong-Ming Hsu","doi":"10.1128/mbio.01864-24","DOIUrl":"10.1128/mbio.01864-24","url":null,"abstract":"&lt;p&gt;&lt;p&gt;&lt;i&gt;Trichomonas vaginalis&lt;/i&gt; is the etiologic agent of trichomoniasis, one of the most common non-viral sexually transmitted infections globally. Our previous work reported the role of phosphatidylinositol 4,5-bisphosphates (PIP&lt;sub&gt;2&lt;/sub&gt;) signaling in the actin-dependent pathogenicity of &lt;i&gt;T. vaginalis&lt;/i&gt;. This study further demonstrated that iron transiently regulated &lt;i&gt;T. vaginalis&lt;/i&gt; phosphatidylinositol-4-phosphate 5-kinase (&lt;i&gt;Tv&lt;/i&gt;PI4P5K) proteostasis and its complex formation with an active ADP ribosylation factor &lt;i&gt;Tv&lt;/i&gt;Arf220, facilitating co-trafficking to the plasma membrane, crucial for PIP&lt;sub&gt;2&lt;/sub&gt; production. In dominant-active HA-&lt;i&gt;Tv&lt;/i&gt;Arf220 Q71L mutant, &lt;i&gt;Tv&lt;/i&gt;PI4P5K plasma membrane trafficking, PIP&lt;sub&gt;2&lt;/sub&gt; production, and intracellular calcium levels were increased, while these processes were inhibited in dominant-negative T31N mutant or those by Brefeldin A (BFA) treatment. Additionally, PIP&lt;sub&gt;2&lt;/sub&gt; replenishment reversed these inhibitions in the T31N mutant, suggesting the critical role of &lt;i&gt;Tv&lt;/i&gt;Arf220 activation in PIP&lt;sub&gt;2&lt;/sub&gt;-calcium signaling. Also, T31N mutant and BFA treatment impaired actin dynamics and cytoskeleton-dependent processes in &lt;i&gt;T. vaginalis&lt;/i&gt;, further linking the role of &lt;i&gt;Tv&lt;/i&gt;Arf220 to PIP&lt;sub&gt;2&lt;/sub&gt;-calcium-dependent actin dynamics. Beyond cytoadherence, during host-parasite interactions, &lt;i&gt;Tv&lt;/i&gt;Arf220 influenced both contact-dependent and -independent cytotoxicity, as well as phagocytotic capacity, contributing to the cytopathogenesis of human vaginal epithelial cells. Our findings underscore the key upstream regulation mechanisms of the PIP&lt;sub&gt;2&lt;/sub&gt; signaling, orchestrating the interplay between &lt;i&gt;Tv&lt;/i&gt;Arf220-PIP&lt;sub&gt;2&lt;/sub&gt;-calcium signaling and downstream actin cytoskeleton-driven pathogenicity in &lt;i&gt;T. vaginalis&lt;/i&gt;.IMPORTANCE&lt;i&gt;Trichomonas vaginalis&lt;/i&gt; actin cytoskeleton-centric pathogenicity is regulated by the phosphatidylinositol 4,5-bisphosphates (PIP&lt;sub&gt;2&lt;/sub&gt;)-triggered calcium signaling cascade in response to environmental iron, though the detailed mechanism by which iron modulates PIP&lt;sub&gt;2&lt;/sub&gt; signaling remains unclear. Our findings reveal that iron rapidly induces &lt;i&gt;T. vaginalis&lt;/i&gt; phosphatidylinositol-4-phosphate 5-kinase (&lt;i&gt;Tv&lt;/i&gt;PI4P5K) translation followed by its degradation, while simultaneously activating &lt;i&gt;Tv&lt;/i&gt;Arf220 binding, which facilitates &lt;i&gt;Tv&lt;/i&gt;PI4P5K localization to the plasma membrane for PIP&lt;sub&gt;2&lt;/sub&gt; production. In contrast to the &lt;i&gt;Tv&lt;/i&gt;Arf220 Q71L mutant, the reduced PIP&lt;sub&gt;2&lt;/sub&gt; production, intracellular calcium, actin assembly, morphogenesis, and cytoadherence in the dominant-negative T31N mutant were recovered by PIP&lt;sub&gt;2&lt;/sub&gt; supplementation, indicating the essential role of &lt;i&gt;Tv&lt;/i&gt;Arf220 in PIP&lt;sub&gt;2&lt;/sub&gt;-dependent calcium signaling. Additionally, the contact-dependent or -independent cytotoxicity, along with the phagocytosis, was impaired in the &lt;i&gt;Tv&lt;/i&gt;PI4P5K- or &lt;i&gt;Tv&lt;/i&gt;Arf220-deficien","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0186424"},"PeriodicalIF":5.1,"publicationDate":"2025-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11796385/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142876994","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Are we serologically prepared against an avian influenza pandemic and could seasonal flu vaccines help us?","authors":"Iván Sanz-Muñoz, Javier Sánchez-Martínez, Carla Rodríguez-Crespo, Corina S Concha-Santos, Marta Hernández, Silvia Rojo-Rello, Marta Domínguez-Gil, Ahmed Mostafa, Luis Martinez-Sobrido, Jose M Eiros, Aitor Nogales","doi":"10.1128/mbio.03721-24","DOIUrl":"10.1128/mbio.03721-24","url":null,"abstract":"<p><p>The current situation with H5N1 highly pathogenic avian influenza virus (HPAI) is causing a worldwide concern due to multiple outbreaks in wild birds, poultry, and mammals. Moreover, multiple zoonotic infections in humans have been reported. Importantly, HPAI H5N1 viruses with genetic markers of adaptation to mammals have been detected. Together with HPAI H5N1, avian influenza viruses H7N9 (high and low pathogenic) stand out due to their high mortality rates in humans. This raises the question of how prepared we are serologically and whether seasonal vaccines are capable of inducing protective immunity against these influenza subtypes. An observational study was conducted in which sera from people born between years 1925-1967, 1968-1977, and 1978-1997 were collected before or after 28 days or 6 months post-vaccination with an inactivated seasonal influenza vaccine. Then, hemagglutination inhibition, viral neutralization, and immunoassays were performed to assess the basal protective immunity of the population as well as the ability of seasonal influenza vaccines to induce protective responses. Our results indicate that subtype-specific serological protection against H5N1 and H7N9 in the representative Spanish population evaluated was limited or nonexistent. However, seasonal vaccination was able to increase the antibody titers to protective levels in a moderate percentage of people, probably due to cross-reactive responses. These findings demonstrate the importance of vaccination and suggest that seasonal influenza vaccines could be used as a first line of defense against an eventual pandemic caused by avian influenza viruses, to be followed immediately by the use of more specific pandemic vaccines.IMPORTANCEInfluenza A viruses (IAV) can infect and replicate in multiple mammalian and avian species. Avian influenza virus (AIV) is a highly contagious viral disease that occurs primarily in poultry and wild water birds. Due to the lack of population immunity in humans and ongoing evolution of AIV, there is a continuing risk that new IAV could emerge and rapidly spread worldwide, causing a pandemic, if the ability to transmit efficiently among humans was gained. The aim of this study is to analyze the basal protection and presence of antibodies against IAV H5N1 and H7N9 subtypes in the population from different ages. Moreover, we have evaluated the humoral response after immunization with a seasonal influenza vaccine. This study is strategically important to evaluate the level of population immunity that is a major factor when assessing the impact that an emerging IAV strain would have, and the role of seasonal vaccines to mitigate the effects of a pandemic.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0372124"},"PeriodicalIF":5.1,"publicationDate":"2025-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11796349/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142914969","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Delivery determinants of an <i>Acinetobacter baumannii</i> type VI secretion system bifunctional peptidoglycan hydrolase.","authors":"Valeriya Bezkorovayna, Brooke K Hayes, Francesca N Gillett, Amy Wright, David I Roper, Marina Harper, Sheena McGowan, John D Boyce","doi":"10.1128/mbio.02627-24","DOIUrl":"10.1128/mbio.02627-24","url":null,"abstract":"<p><p><i>Acinetobacter baumannii</i> is a Gram-negative opportunistic pathogen and is a common cause of nosocomial infections. The increasing development of antibiotic resistance in this organism is a global health concern. The <i>A. baumannii</i> clinical isolate AB307-0294 produces a type VI secretion system (T6SS) that delivers three antibacterial effector proteins that give this strain a competitive advantage against other bacteria in polymicrobial environments. Each effector, Tse15, Tde16, and Tae17, is delivered <i>via</i> a non-covalent interaction with a specific T6SS VgrG protein (VgrG15, VgrG16, and VgrG17, respectively). Here we define the regions of interaction between Tae17 and its cognate delivery protein VgrG17 and identify that amino acids G1069 and W1075 in VgrG17 are essential for Tae17 delivery <i>via</i> the T6SS, the first time such specific delivery determinants of T6SS cargo effectors have been defined. Furthermore, we determine that the Tae17 effector is a multidomain, bifunctional, peptidoglycan-degrading enzyme that has both amidase activity, which targets the sugar-peptide bonds, and lytic transglycosylase activity, which targets the peptidoglycan sugar backbone. Moreover, we show that the Tae17 transglycosylase activity is more important than amidase activity for the killing of <i>Escherichia coli</i>. This study provides molecular insight into how the T6SS allows <i>A. baumannii</i> strains to gain dominance in polymicrobial communities and thus improve their chances of survival and transmission.IMPORTANCEWe have shown that the <i>Acinetobacter baumannii</i> T6SS effector Tae17 is a modular, bifunctional, peptidoglycan-degrading enzyme that has both lytic transglycosylase and amidase activities. Both activities contribute to the ability to degrade peptidoglycan, but the transglycosylase activity was more important for the killing of <i>Escherichia coli</i>. We have defined the specific regions of Tae17 and its cognate delivery protein VgrG17 that are necessary for the non-covalent interactions and, for the first time, identified specific amino acids essential for T6SS cargo effector delivery. This work contributes to our molecular understanding of bacterial competition strategies in polymicrobial environments and may provide a window to design new therapeutic approaches for combating infection by <i>A. baumannii</i>.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0262724"},"PeriodicalIF":5.1,"publicationDate":"2025-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11796386/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142914979","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Overcoming barriers for investigating nickel-pincer nucleotide cofactor-related enzymes.","authors":"Jorge L Nevarez, Aiko Turmo, Santhosh Gatreddi, Swati Gupta, Jian Hu, Robert P Hausinger","doi":"10.1128/mbio.03404-24","DOIUrl":"10.1128/mbio.03404-24","url":null,"abstract":"<p><p>The nickel-pincer nucleotide (NPN) cofactor is a modified pyridinium mononucleotide that tri-coordinates nickel and is crucial for the activity of certain racemases and epimerases. LarB, LarC, and LarE are responsible for NPN synthesis, with the cofactor subsequently installed into LarA homologs. Hurdles for investigating the functional properties of such proteins arise from the difficulty of obtaining the active, NPN cofactor-loaded enzymes and in assaying their diverse reactivities. Here, we show that when the <i>Lactiplantibacillus plantarum lar</i> genes are cloned into the Duet expression system and cultured in <i>Escherichia coli</i>, they confer lactate racemase activity to the cells. By replacing <i>L. plantarum larA</i> with related genes from other microorganisms, this system allows for the generation of active LarA homologs. Furthermore, the Duet system enables the functional testing of LarB, LarC, and LarE homologs from other microorganisms. In addition to applying the Duet expression system for synthesis of active, NPN cofactor-containing enzymes in <i>E. coli</i>, we demonstrate that circular dichroism spectroscopy provides a broadly applicable means of assaying these enzymes. By selecting a wavelength of high molar ellipticity and low absorbance for a given 2-hydroxy acid substrate enantiomer, the conversion of one enantiomer/epimer into the other can be monitored for LarA homologs without the need for any coupling enzymes or reagents. The methods discussed here further our abilities to investigate the unique activities of Lar proteins.</p><p><strong>Importance: </strong>Enzymes containing the nickel-pincer nucleotide (NPN) cofactor are prevalent in a wide range of microorganisms and catalyze various critical biochemical reactions, yet they remain underexplored due, in part, to limitations in current research methodologies. The two significant advancements described here, the heterologous production of active NPN-cofactor containing enzymes in <i>Escherichia coli</i> and the use of a circular dichroism-based assay to monitor enzyme activities, expand our capacity to analyze these enzymes. Such additional detailed characterization will deepen our understanding of the diverse chemistry catalyzed by the NPN cofactor and potentially uncover novel roles for this organometallic species in microbial metabolism.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0340424"},"PeriodicalIF":5.1,"publicationDate":"2025-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11796402/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142829219","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Ethanolamine-induced assembly of microcompartments is required for <i>Fusobacterium nucleatum</i> virulence.","authors":"Dana S Franklin, Yi-Wei Chen, Yimin Chen, Manuel Wittchen, Angela Agnew, Alexis Luu, Julian P Whitelegge, Z Hong Zhou, Andreas Tauch, Asis Das, Hung Ton-That","doi":"10.1128/mbio.03405-24","DOIUrl":"10.1128/mbio.03405-24","url":null,"abstract":"<p><p>Many bacteria metabolize ethanolamine as a nutrient source through cytoplasmic organelles named bacterial microcompartments (BMCs). Here we investigated the molecular assembly, regulation, and function of BMCs in <i>Fusobacterium nucleatum-</i>a Gram-negative oral pathobiont that is associated with adverse pregnancy outcomes. The <i>F. nucleatum</i> genome harbors a conserved ethanolamine utilization (<i>eut</i>) locus with 21 genes that encode several putative BMC shell proteins and a two-component signal transduction system (TCS), in addition to the enzymes for ethanolamine transport and catabolism. We show that the expression of most of these genes and BMC formation are highly increased in wild-type fusobacteria when cultured in the presence of ethanolamine as a nutrient source. Deletion of the response regulator EutV eliminated this induction of <i>eut</i> mRNAs and BMCs, thus demonstrating that BMC formation is transcriptionally regulated by the TCS EutV-EutW in response to ethanolamine. Mass spectrometry of isolated BMCs unveiled the identity of the constituent proteins EutL, EutM₁, EutM₂, and EutN. Consistent with the role of these proteins in BMC assembly and metabolism, deletion of <i>eutN</i>, <i>eutL</i>/<i>eutM₁</i>/<i>eutM₂</i>, or <i>eutL</i>/<i>eutM₁</i>/<i>eutM₂</i>/<i>eutN</i> not only affected BMC formation but also ethanolamine utilization, causing cell growth defects with ethanolamine as a nutrient. BMCs are also assembled in fusobacteria cultured with placental cells or the culture media, a process that is dependent on the BMC shell proteins. Significantly, we show that the <i>eutN</i> mutant is defective in inducing preterm birth in a mouse model. Together, these results establish that the BMC-mediated metabolism of ethanolamine is critical for fusobacterial virulence.</p><p><strong>Importance: </strong>The oral anaerobe <i>Fusobacterium nucleatum</i> can spread to distal internal organs, such as the colon and placenta, thereby promoting the development of colorectal cancer and inducing preterm birth, respectively. Yet, how this opportunistic pathogen adapts to the various metabolically distinct host cellular niches remains poorly understood. We demonstrated here that this microbe assembles specialized metabolic organelles, termed bacterial microcompartments (BMCs), to utilize environmental ethanolamine (EA) as a key environmental nutrient source. The formation of <i>F. nucleatum</i> BMCs, containing BMC shell proteins EutLM1M2N, is controlled by a two-component system, EutV-EutW, responsive to EA. Significantly, this ability of <i>F. nucleatum</i> to form BMCs in response to EA is crucial for its pathogenicity evidenced by the fact that the genetic disruption of BMC formation reduces fusobacterial virulence in a mouse model of preterm birth.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0340524"},"PeriodicalIF":5.1,"publicationDate":"2025-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11796344/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142876501","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Influence of snow cover on albedo reduction by snow algae.","authors":"Pablo Almela, James J Elser, J Joseph Giersch, Scott Hotaling, Trinity L Hamilton","doi":"10.1128/mbio.03630-24","DOIUrl":"10.1128/mbio.03630-24","url":null,"abstract":"<p><p>Snow algae darken the surface of snow, reducing albedo and accelerating melt. However, the impact of subsurface snow algae (e.g., when cells are covered by recent snowfall) on albedo is unknown. Here, we examined the impact of subsurface snow algae on surface energy absorption by adding up to 2 cm of clean snow to surface algal blooms and measuring reflectivity. Surprisingly, snow algae still absorb significant energy across an array of wavelengths when snow-covered. Furthermore, the scale of this effect correlates with algal cell densities and chlorophyll-a concentrations. Collectively, our results suggest that darkening by subsurface snow algae lowers albedo and thus potentially accelerates snowmelt even when the algae is snow-covered. Impacts of subsurface algae on melt await assessment. This implies that snow algae play a larger role in cryosphere melt than investigations of surface-only reflectance would suggest.</p><p><strong>Importance: </strong>This study addresses a gap in research by examining the impact of subsurface snow algae on snow albedo, which affects snowmelt rates. Previous studies have focused on visible surface blooms, leaving the effects of hidden algae unquantified. Our findings reveal that snow algae beneath the surface can still absorb energy across various wavelengths, accelerating melt even when not visible to the naked eye. This suggests that spectral remote sensing can detect these hidden algae, although their biomass might be underestimated. Understanding how subsurface snow algae influence albedo and snowmelt is crucial for accurate predictions of meltwater runoff, which impacts alpine ecosystems, glacier health, and water resources. Accurate projections are essential for managing freshwater supplies for agriculture, drinking water, and other vital uses. Thus, further investigation into subsurface snow algae is necessary to improve our understanding of their role in snow albedo reduction and water resource management.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0363024"},"PeriodicalIF":5.1,"publicationDate":"2025-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11796388/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142978616","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Autoinducer-2 enhances the defense of <i>Vibrio furnissii</i> against oxidative stress and DNA damage by modulation of c-di-GMP signaling via a two-component system.","authors":"Heng Zhang, Wenjin Zhao, Wenguang Yang, Huimin Zhang, Xinyu Qian, Kai Sun, Qiao Yang, Xihui Shen, Lei Zhang","doi":"10.1128/mbio.02922-24","DOIUrl":"10.1128/mbio.02922-24","url":null,"abstract":"<p><p>As a universal language across the bacterial kingdom, the quorum sensing signal autoinducer-2 (AI-2) can coordinate many bacterial group behaviors. However, unknown AI-2 receptors in bacteria may be more than what has been discovered so far, and there are still many unknown functions for this signal waiting to be explored. Here, we have identified a membrane-bound histidine kinase of the pathogenic bacterium <i>Vibrio furnissii</i>, AsrK, as a receptor that specifically detects AI-2 under low boron conditions. In contrast with another well-known AI-2 receptor LuxP that recognizes the borated form of AI-2, AsrK is found to show higher affinity with AI-2 under borate-depleted conditions, and thus boron has a negative effect on AI-2 sensing by AsrK in regulation of the biofilm and motility phenotypes. AI-2 binds to the extracytoplasmic dCache_1 domain of AsrK to inhibit its autokinase activity, thus decreasing the phosphorylation level of its cognate response regulator AsrR and activating the phosphodiesterase activity of AsrR to degrade the cellular second messenger cyclic di-GMP (c-di-GMP). AI-2 perception by the AsrK-AsrR system remarkably reduces intracellular c-di-GMP levels and enhances tolerance of <i>V. furnissii</i> to oxidative stress and DNA damage by upregulating the transcription of universal stress proteins including UspA1, UspA2, and UspE. Our study reveals a previously unrecognized mechanism for AI-2 detection in bacteria and also provides new insights into the important role of AI-2 in bacterial defense against oxidative stress and DNA damage.IMPORTANCEThe QS signal AI-2 is widely synthesized in bacteria and has been implicated in the regulation of numerous bacterial group behaviors. However, in contrast to the wide distribution of this signal, its receptors have only been found in a small number of bacterial species, and the underlying mechanisms for the detection of and response to AI-2 remain elusive in most bacteria. It is worth noting that the periplasmic protein LuxP is the uniquely identified receptor for AI-2 in <i>Vibrio</i> spp. Here, we identify a second type of AI-2 receptor, a membrane-bound histidine kinase with a periplasmic dCache_1 sensory domain, in a member of the genus <i>Vibrio</i>, and thus show that AI-2 enhances the defense of <i>V. furnissii</i> against oxidative stress and DNA damage by modulation of c-di-GMP signaling via the AsrK-AsrR two-component system. Our results reveal a previously unrecognized AI-2 sensing mechanism and expand our understanding of the physiological roles of AI-2 in bacteria.</p>","PeriodicalId":18315,"journal":{"name":"mBio","volume":" ","pages":"e0292224"},"PeriodicalIF":5.1,"publicationDate":"2025-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11796354/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143008206","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}