Journal of Bacteriology最新文献

{"title":"A novel polysaccharide in the envelope of <i>S. aureus</i> influences the septal secretion of preproteins with a YSIRK/GXXS motif.","authors":"Amany M Ibrahim, Dominique Missiakas","doi":"10.1128/jb.00478-24","DOIUrl":"https://doi.org/10.1128/jb.00478-24","url":null,"abstract":"<p><p>Bacteria transport proteins across the plasma membrane to assemble their envelope, acquire nutrients, and establish appropriate interactions with their environment. The majority of these proteins are synthesized as precursors with a cleavable N-terminal signal sequence for recognition by the Sec machinery. In <i>Staphylococcus aureus</i>, a small subset of secreted precursors carries a YSIRK/GXXS motif. This motif provides a pre-translocation function by promoting the targeting of precursors to septal membranes, but the <i>trans-</i>acting factors that regulate such spatial distribution are not known. Here, we used immunofluorescence-microscopy to compare the spatial trafficking of Staphylococcal protein A (SpA), an abundant YSIRK/GXXS bearing precursor, between mutants of an arranged transposon library. This genetic search identified a cluster of five genes predicted to encode enzymes responsible for the synthesis of a novel surface polymer referred to as Staphylococcal surface carbohydrate, Ssc. Mutants in the <i>ssc</i> gene cluster no longer restrict the secretion of SpA into the cross-walls of <i>S. aureus. ssc</i> mutants replicate like wild-type bacteria unless grown in phosphate-limited conditions, and do not contribute to virulence when examined in a mouse model of bloodstream infection. Together, our observations suggest that <i>S. aureus</i> may encode a minor, phosphate-free carbohydrate, and propose a possible assembly pathway for this polymer.</p><p><strong>Importance: </strong>Gram-positive bacteria assemble peptidoglycan-linked polymers known as wall teichoic acids (WTA). Both <i>Staphylococcus aureus</i> and <i>Bacillus subtilis</i> elaborate WTAs made of poly-glycerol or poly-ribitol phosphates. WTAs contribute to cell shape maintenance, cation homeostasis, and resistance to antimicrobial compounds. Yet, <i>B. subtilis</i> replaces its phosphate-rich polymer with minor teichuronic acids whose functions remain elusive. <i>S. aureus</i> also encodes a minor wall polymer that may be required for growth under phosphate-limited condition. Here, we find that this polymer could help define the composition of the septal compartment, the site of cell division also used to recruit preproteins with a YSIRK/GXXS motif. Thus, the envelope of <i>S. aureus</i> may be more complex than previously thought with minor wall polymers contributing some discrete functions.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0047824"},"PeriodicalIF":2.7,"publicationDate":"2025-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143052538","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Use of analytical strategies to understand spatial chemical variation in bacterial surface communities.","authors":"Abigail A Weaver, Joshua D Shrout","doi":"10.1128/jb.00402-24","DOIUrl":"https://doi.org/10.1128/jb.00402-24","url":null,"abstract":"<p><p>Not only do surface-growing microbes such as biofilms display specific traits compared to planktonic cells, but also they display many heterogeneous behaviors over many spatial and temporal contexts. While the application of molecular genetics tools to extract or visualize gene expression or regulatory function data is now common in studying surface growth, the use of analytical chemistry tools to visualize the spatiotemporal distribution of chemical products synthesized by these surface microbes is less common. Here, we review chemical imaging tools that have been used to inform our understanding of surface-growing microbes. We highlight the use of confocal Raman Microscopy, surface-enhanced Raman spectroscopy, matrix-assisted laser desorption/ionization, secondary ion mass spectrometry, desorption electrospray ionization, and electrochemical imaging that have been applied to assess two-dimensional chemical profiles of bacteria. We specifically discuss the use of these tools to study rhamnolipids, alkylquinolones, and phenazines of the bacterium <i>Pseudomonas aeruginosa</i>.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0040224"},"PeriodicalIF":2.7,"publicationDate":"2025-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143052594","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Laboratory evolution of <i>E. coli</i> with a natural vitamin B₁₂ analog reveals roles for cobamide uptake and adenosylation in methionine synthase-dependent growth.","authors":"Kenny C Mok, Zachary F Hallberg, Rebecca R Procknow, Michiko E Taga","doi":"10.1128/jb.00284-24","DOIUrl":"https://doi.org/10.1128/jb.00284-24","url":null,"abstract":"<p><p>Bacteria encounter chemically similar nutrients in their environment, which impact their growth in distinct ways. Among such nutrients are cobamides, the structurally diverse family of cofactors related to vitamin B₁₂ (cobalamin), which function as cofactors for diverse metabolic processes. Given that different environments contain varying abundances of different cobamides, bacteria are likely to encounter cobamides that enable them to grow robustly and also those that do not function efficiently for their metabolism. To gain insights into how bacteria might respond under the latter conditions, we performed a laboratory evolution of a cobamide-dependent strain of <i>Escherichia coli</i> with pseudocobalamin (pCbl), a cobamide that <i>E. coli</i> uses less effectively than cobalamin for MetH-dependent methionine synthesis. Propagation and sequencing of nine independent lines identified potential genetic adaptations in cobamide-related genes that improved growth with less-preferred cobamides. We constructed targeted mutants to validate these findings and found that increasing the expression of the outer membrane cobamide transporter BtuB is beneficial during growth under cobamide-limiting conditions. Unexpectedly, we also found that overexpression of the cobamide adenosyltransferase BtuR confers a specific growth advantage with pCbl. Characterization of the latter phenotype revealed that BtuR and adenosylated cobamides contribute to optimal MetH-dependent growth. Together, these findings improve our understanding of how bacteria expand their cobamide-dependent metabolic potential.IMPORTANCEIn nature, bacteria commonly experience fluctuations in the availability of required nutrients. Thus, their environment often contains nutrients that are insufficient in quantity or that function poorly in their metabolism. Cobamides, the vitamin B₁₂ family of cofactors, are ideal for investigating the influence of nutrient quality on bacterial growth. We performed a laboratory evolution experiment in <i>E. coli</i> with a less-preferred cobamide to examine whether and how bacteria can improve their growth with less ideal nutrients. We found that overexpression of genes for cobamide uptake and modification are genetic adaptations that improve growth under these conditions. Given that cobamides are key shared metabolites in microbial communities, our results reveal insights into bacterial interactions and competition for nutrients.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0028424"},"PeriodicalIF":2.7,"publicationDate":"2025-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143052589","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"How FocA facilitates fermentation and respiration of formate by <i>Escherichia coli</i>.","authors":"R Gary Sawers","doi":"10.1128/jb.00502-24","DOIUrl":"https://doi.org/10.1128/jb.00502-24","url":null,"abstract":"<p><p>Formic acid is an important source of reductant and energy for many microorganisms. Formate is also produced as a fermentation product, e.g., by enterobacteria like <i>Escherichia coli</i>. As such, formic acid shares many features in common with dihydrogen, explaining perhaps why their metabolism and physiology show considerable overlap. At physiological pH, formic acid is mainly present as the dissociated formate anion and therefore cannot diffuse freely across the cytoplasmic membrane. Specific and bidirectional translocation of formate across the cytoplasmic membrane is, however, achieved in <i>E. coli</i> by the homopentameric membrane protein, FocA. Formic acid translocation from the cytoplasm into the periplasm (efflux) serves to maintain a near-neutral cytosolic pH and to deliver formate to the periplasmically-oriented respiratory formate dehydrogenases, Fdh-N and Fdh-O. These enzymes oxidize formate, with the electrons being used to reduce nitrate, oxygen, or other acceptors. In the absence of exogenous electron acceptors, formate is re-imported into the cytoplasm by FocA, where it is sensed by the transcriptional regulator FhlA, resulting in induction of the formate regulon. The genes and operons of the formate regulon encode enzymes necessary to assemble the formate hydrogenlyase complex, which disproportionates formic acid into H₂ and CO₂. Combined, these mechanisms of dealing with formate help to maintain cellular pH homeostasis and are suggested to maintain the proton gradient during growth and in stationary phase cells. This review highlights our current understanding of how formate metabolism helps balance cellular pH, how it responds to the redox status, and how it helps conserve energy.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0050224"},"PeriodicalIF":2.7,"publicationDate":"2025-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143046873","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The NmpRSTU multi-component signaling system of <i>Myxococcus xanthus</i> regulates expression of an oxygen utilization regulon.","authors":"Colin T McAllister, Allison M Ronk, Mason J Stenzel, John R Kirby, Daniel J Bretl","doi":"10.1128/jb.00280-24","DOIUrl":"https://doi.org/10.1128/jb.00280-24","url":null,"abstract":"<p><p><i>Myxococcus xanthus</i> has numerous two-component signaling systems (TCSs), many of which regulate the complex social behaviors of this soil bacterium. A subset of TCSs consists of NtrC-like response regulators (RRs) and their cognate histidine sensor kinases (SKs). We have previously demonstrated that a multi-component, phosphorelay TCS named NmpRSTU plays a role in <i>M. xanthus</i> social motility. NmpRSTU was discovered through a screen that identified mutations in <i>nmp</i> genes that restored Type-IV pili-dependent motility to a nonmotile strain. The Nmp pathway begins with the SK NmpU, which is predicted to be active in the presence of oxygen. NmpU phosphorylates another SK, NmpS, a hybrid kinase containing an RR domain and a HisKA-CA domain. These two kinases work in a reciprocal fashion: when NmpU is active, NmpS is inactive, and vice versa. Finally, the phosphorelay culminates in NmpS phosphorylating the NtrC-like RR NmpR. To better understand the role of NmpRSTU in <i>M. xanthus</i> physiology, we determined the NmpR regulon by combining <i>in silico</i> predictions of the NmpR consensus binding sequence with <i>in vitro</i> electromobility shift assays (EMSAs) and <i>in vivo</i> transcriptional reporters. We identified several NmpR-dependent, upregulated genes likely to be important in oxygen utilization. Additionally, we demonstrate NmpRSTU plays a role in fruiting body development, suggesting a role for oxygen sensing in this behavior. We propose that NmpRSTU senses oxygen-limiting conditions, and NmpR upregulates genes associated with optimal utilization of that oxygen. This may be necessary for <i>M. xanthus</i> physiology and behaviors in the highly dynamic soil where oxygen concentrations vary dramatically.</p><p><strong>Importance: </strong>Bacteria use two-component signaling systems (TCSs) to respond to a multitude of environmental signals and subsequently regulate complex cellular physiology and behaviors. <i>Myxococcus xanthus</i> is a ubiquitous soil bacterium that encodes numerous two-component systems to respond to the conditions of its soil environment and coordinate multicellular behaviors such as coordinated motility, microbial predation, fruiting body development, and sporulation. To better understand how this bacterium uses a two-component system that has been linked to the sensing of oxygen concentrations, NmpRSTU, we determined the gene regulatory network of this system. We identified several genes regulated by NmpR that are likely important in oxygen utilization and for the <i>M. xanthus</i> response to varied oxygen concentrations in the dynamic soil environment.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0028024"},"PeriodicalIF":2.7,"publicationDate":"2025-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143046877","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Gut phages and their interactions with bacterial and mammalian hosts.","authors":"Marshall Godsil, Nathaniel L Ritz, Siddarth Venkatesh, Alexander J Meeske","doi":"10.1128/jb.00428-24","DOIUrl":"https://doi.org/10.1128/jb.00428-24","url":null,"abstract":"<p><p>The mammalian gut microbiome is a dense and diverse community of microorganisms that reside in the distal gastrointestinal tract. In recent decades, the bacterial members of the gut microbiome have been the subject of intense research. Less well studied is the large community of bacteriophages that reside in the gut, which number in the billions of viral particles per gram of feces, and consist of considerable unknown viral \"dark matter.\" This community of gut-residing bacteriophages, called the gut \"phageome,\" plays a central role in the gut microbiome through predation and transformation of native gut bacteria, and through interactions with their mammalian hosts. In this review, we will summarize what is known about the composition and origins of the gut phageome, as well as its role in microbiome homeostasis and host health. Furthermore, we will outline the interactions of gut phages with their bacterial and mammalian hosts, and plot a course for the mechanistic study of these systems.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0042824"},"PeriodicalIF":2.7,"publicationDate":"2025-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143023438","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"LD-transpeptidase-mediated cell envelope remodeling enables developmental transitions and survival in <i>Coxiella burnetii</i> and <i>Legionella pneumophila</i>.","authors":"Dipak Kathayat, Yujia Huang, Joee Denis, Benjamin Rudoy, Hana Schwarz, Jacob Szlechter","doi":"10.1128/jb.00247-24","DOIUrl":"https://doi.org/10.1128/jb.00247-24","url":null,"abstract":"&lt;p&gt;&lt;p&gt;&lt;i&gt;Coxiella burnetii&lt;/i&gt; and &lt;i&gt;Legionella pneumophila&lt;/i&gt; are two phylogenetically related bacterial pathogens that exhibit extreme intrinsic resistance when they enter into a dormancy-like state. This enables both pathogens to survive extended periods in growth-limited environments. Survival is dependent upon their ability to undergo developmental transitions into two phenotypically distinct variants, one specialized for intracellular replication and another for prolonged survival in the environment and host. We currently lack an understanding of the mechanisms that mediate these developmental transitions. Here, we performed peptidoglycan (PG) glycoproteome analysis and showed significant enrichment of PG structures catalyzed by LD-transpeptidases (LDTs) in the survival variants of &lt;i&gt;C. burnetii&lt;/i&gt; and &lt;i&gt;L. pneumophila&lt;/i&gt;. This is supported by the upregulation of LDTs, resulting in susceptibility to carbapenem antibiotics. Furthermore, deletion of the most upregulated LDT, &lt;i&gt;lpg&lt;/i&gt;1386, in &lt;i&gt;L. pneumophila&lt;/i&gt; significantly changes PG architecture, survival, and susceptibility to antibiotics. Significantly regulated by RpoS, a stationary-phase sigma factor, LDT-dependent PG remodeling is differentially activated by the host intracellular growth environment compared to axenic culture. In addition, β-barrel tethering, a newly discovered mechanism of LDT-mediated cell envelope stabilization, seems not to be specific to the survival variants. Interestingly, an outer membrane (OM) long-chain fatty acid transporter (Lpg1810) is tethered to PG in &lt;i&gt;L. pneumophila&lt;/i&gt;. Collectively, these findings show that LDT-mediated PG remodeling is a major determinant of developmental transitions and survival in &lt;i&gt;C. burnetii&lt;/i&gt; and &lt;i&gt;L. pneumophila&lt;/i&gt;. Understanding this mechanism might inform new therapeutic approaches for treating chronic infections caused by these pathogens, as well as suggest new methods to decontaminate environmental reservoirs during outbreaks.IMPORTANCE&lt;i&gt;Coxiella burnetii&lt;/i&gt; and &lt;i&gt;L. pneumophila&lt;/i&gt; cause Q Fever and Legionnaire's disease in humans, respectively. There is a lack of effective treatments for fatal chronic infections caused by these pathogens, particularly chronic Q Fever. These bacteria survive long term in nutrient-limited environments by differentiating into phenotypically distinct survival variants. Our study revealed that LDTs, a group of PG remodeling enzymes, play a prominent role in the phenotypic differentiations of these bacteria. We show that LDT-targeting carbapenems are effective against the survival variants, thus demanding the exploration of carbapenems for treating chronic infections caused by these pathogens. We report the tethering of a unique OM fatty acid transporter to PG in &lt;i&gt;L. pneumophila&lt;/i&gt; that could indicate a novel function of tethering, that is, the uptake of nutrient substrates. Homologs of this transporter are widely present in the Methylobacteriaceae family of bacteria kn","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0024724"},"PeriodicalIF":2.7,"publicationDate":"2025-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143023388","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The GacS/GacA two-component system strongly regulates antimicrobial competition mechanisms of <i>Pseudomonas fluorescens</i> MFE01 strain.","authors":"Charly A Dupont, Yvann Bourigault, Héloïse Biziere-Maco, Amine M Boukerb, Xavier Latour, Corinne Barbey, Julien Verdon, Annabelle Merieau","doi":"10.1128/jb.00388-24","DOIUrl":"https://doi.org/10.1128/jb.00388-24","url":null,"abstract":"<p><p><i>Pseudomonas fluorescens</i> MFE01 is an environmental bacterium characterized by an hyperactive type 6 secretion system (T6SS) and a strong emission of volatile organic compounds (VOCs). In a previous study, a transposition mutant, 3H5, exhibited an inactive T6SS and altered VOC emission. In 3H5, the interruption of <i>trpE</i> gene by the transposon was insufficient to explain these phenotypes. To determine the actual impact of this insertion, a comparative transcriptomic analysis was performed on the two-component system GacS/GacA, known to influence numerous phenotypes in <i>Pseudomonas</i>. The results demonstrated that the <i>gacS</i> gene is less expressed in 3H5 than in MFE01. Phenotypic analysis of a <i>gacS</i> deletion mutant, Δ<i>gacS</i>, confirmed many similarities between Δ<i>gacS</i> and 3H5. Indeed, Δ<i>gacS</i> exhibited an inactive T6SS and an altered VOC emission profile. In-depth analysis of volatilomes and phenotypes correlated with the decrease in <i>gacS</i> transcription, highlighting that the emission of 1-undecene is under the strict control of GacS/GacA. This study confirms that 1-undecene is not the sole volatile molecule responsible for MFE01's inhibition of <i>Legionella</i>. Moreover, MFE01 has antimicrobial activity against the phytopathogenic oomycetes <i>Phytophthora infestans</i> via hydrogen cyanide (HCN) emission, which is also controlled by GacS. In MFE01, GacS/GacA is also a partial positive regulator of other VOC emission, whose reduced emission in 3H5 coincides with the decrease in <i>gacS</i> transcription.</p><p><strong>Importance: </strong>Our model strain <i>Pseudomonas fluorescens</i> MFE01 uses an active type VI secretion system (T6SS) and volatile compounds (VCs) to outcompete other microorganisms in the natural environment. By investigating the cellular mechanism regulating the production of these weapons, we identified the two-component system GacS/GacA. Indeed, GacS cellular membrane sensor plays a crucial role in regulating T6SS activity and VC emission. Among the latter, 1-undecene and hydrogen cyanide are strong aerial inhibitors of the <i>Legionella</i> human pathogen and the <i>Phytophtora infestans</i> major plant pest, respectively. The aim is to improve the understanding of the regulation of these volatile molecule emission and the critical role of a global regulator in both plant and human health.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0038824"},"PeriodicalIF":2.7,"publicationDate":"2025-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143023463","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"<i>Francisella tularensis</i> universal stress protein contributes to persistence during growth arrest and paraquat-induced superoxide stress.","authors":"Benjamin Girardo, Yinshi Yue, Oksana Lockridge, Amanda M Bartling, Lawrence M Schopfer, Leonardo Augusto, Marilynn A Larson","doi":"10.1128/jb.00377-24","DOIUrl":"https://doi.org/10.1128/jb.00377-24","url":null,"abstract":"<p><p><i>Francisella tularensis</i> is one of the most virulent bacterial pathogens known and causes the disease tularemia, which can be fatal if untreated. This zoonotic and intracellular pathogen is exposed to diverse environmental and host stress factors that require an appropriate response to survive. However, the stress tolerance mechanisms used by <i>F. tularensis</i> to persist are not fully understood. To address this aspect, we evaluated the highly conserved <u>u</u>niversal <u>s</u>tress <u>p</u>rotein (Usp) that is encoded by a single-copy gene in <i>F. tularensis</i>, unlike the majority of other bacterial pathogens that produce several to many Usp homologs. We determined that the <i>F. tularensis</i> Usp transcript is unusually stable with a half-life of over 30 minutes, and that <i>usp</i> transcript and protein levels remained abundant when exposed to low pH, nutrient deprivation, hydrogen peroxide, and paraquat. Of these and other stress conditions evaluated, the <i>F. tularensis</i> Δ<i>usp</i> mutant only exhibited reduced survival relative to the wild type during stationary phase and exposure to paraquat, a highly toxic compound that generates superoxide anions and other free radicals. Comparison of transcript levels in untreated and paraquat-treated <i>F. tularensis</i> wild type and Δ<i>usp</i> indicated that Usp contributes to enhanced expression of antioxidant defense genes, <i>oxyR</i> and <i>katG</i>. In summary, the high abundance and stability of Usp provide prompt protection during extended periods of growth arrest and free radical exposure, promoting <i>F. tularensis</i> persistence. We propose that <i>F. tularensis</i> Usp contributes to an adaptive response that prolongs viability and increases the longevity of this zoonotic pathogen in the environment.</p><p><strong>Importance: </strong><i>Francisella tularensis</i> is classified as a Tier 1 select agent due to the low infectious dose, ease of transmission, and potential use as a bioweapon. To better understand the stress defense mechanisms that contribute to the ability of this highly virulent pathogen to persist, we evaluated the conserved <i>F. tularensis</i> <u>u</u>niversal <u>s</u>tress <u>p</u>rotein (Usp). We show that <i>F. tularensis</i> Usp is unusually stable and remains abundant, regardless of the stress conditions tested, differing from other bacterial Usp homologs. We also determined that <i>F. tularensis</i> Usp enhances the expression of several critical antioxidant defense genes and increases survival during paraquat exposure and growth arrest. Determining the factors that promote <i>F. tularensis</i> persistence in the environment is needed to prevent tularemia transmission.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0037724"},"PeriodicalIF":2.7,"publicationDate":"2025-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143023359","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A rhamnose-rich O-antigen of <i>Paraburkholderia phymatum</i> MP20 is required for symbiosis with <i>Mimosa pudica</i>.","authors":"Shashini U Welmillage, Euan K James, Nisha Tak, Sonali Shedge, Lei Huang, Artur Muszyński, Parastoo Azadi, Prasad Gyaneshwar","doi":"10.1128/jb.00422-24","DOIUrl":"https://doi.org/10.1128/jb.00422-24","url":null,"abstract":"<p><p><i>Paraburkholderia phymatum,</i> a β-proteobacterium, forms a nitrogen-fixing symbiosis with many species of the large legume genus <i>Mimosa</i> as well as with common bean (<i>Phaseolus vulgaris</i> L.). <i>Paraburkholderia</i> are considered to have evolved nodulation independently from the well-studied α-proteobacteria symbionts of legumes. However, the detailed mechanisms important for β-rhizobia-legume symbiosis have not yet been determined. In this manuscript, we have sequenced the genome of <i>P. phymatum</i> MP20, a strain isolated from <i>Mimosa pudica</i> nodules, and utilized transposon mutagenesis to identify a mutant that showed delayed and ineffective nodulation of <i>M. pudica</i>. Further analysis revealed that the mutant strain produced an altered lipopolysaccharide lacking rhamnose containing O-antigen. Complementation with the wild-type gene restored the symbiosis. Microscopic analysis of the ineffective nodules showed that the mutant strain did not infect the cortical cells but was restricted to the endodermis. The results suggest that the O-antigen of <i>P. phymatum</i> is important for the bacterial infection of cortical cells and for nodule maturation. Further research will unveil the specific involvement of the glycosyltransferase gene in LPS biosynthesis and its impact on successful nodule formation by <i>P. phymatum</i>.IMPORTANCEThe nitrogen-fixing symbiosis between legumes and rhizobia is important for agricultural and environmental sustainability. The mechanisms of the symbiotic interactions are extensively studied using α-rhizobia. In contrast, mechanisms of symbiotic interactions important for β-rhizobia and their Caesalpinioid (mimosoid) legume hosts are not well known. Here, we describe the genome sequence of <i>P. phymatum</i> MP20<i>,</i> a β-rhizobia isolated from the nodules of <i>M. pudica,</i> and isolation and characterization of a transposon mutant defective in symbiosis. We demonstrate that the O-antigen of the LPS is required for nodulation and symbiotic nitrogen fixation. This study broadens our knowledge of symbiotic interactions in β-rhizobia and will lead to a better understanding of the wider rhizobial-legume symbiosis apart from the α-rhizobia.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0042224"},"PeriodicalIF":2.7,"publicationDate":"2025-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143023416","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}