Journal of Bacteriology最新文献

{"title":"Environmental context defines the physiological contribution of the Tol-Pal system to cell envelope integrity in <i>Acinetobacter baumannii</i>.","authors":"Roberto Jhonatan Olea-Ozuna, Berenice Furlan, Suman Tiwari, Hanling Gong, Augusto C Hunt-Serracin, Michael B Whalen, Orietta Massidda, Nicholas Dillon, Joseph M Boll","doi":"10.1128/jb.00289-26","DOIUrl":"10.1128/jb.00289-26","url":null,"abstract":"<p><p>The gram-negative cell envelope requires coordinated remodeling of the peptidoglycan layer and outer membrane to preserve envelope integrity during growth and division. The conserved Tol-Pal system contributes to envelope maintenance, although the physiological consequences of its loss vary across environmental contexts and among gram-negative bacteria. Here, we examined the contribution of Tol-Pal across diverse growth environments in <i>Acinetobacter baumannii</i>. Loss of Tol-Pal did not cause a substantial population growth defect, and septal peptidoglycan incorporation remained largely preserved under standard laboratory conditions. In contrast, nutrient-rich media, conditions that alter osmotic balance, and a host-like environment exposed defects in cell division organization and cell morphology. Tol-Pal-deficient cells also exhibited modest but reproducible reductions in outer membrane barrier robustness, and disruption of the Mla phospholipid transport system further exacerbated these defects. Consistent with these phenotypes, loss of Tol-Pal reduced bacterial fitness under environmental stress and host-associated models. Together, these findings indicate that Tol-Pal contributes to outer membrane barrier robustness and that additional consequences of its loss become apparent under conditions that challenge the cell envelope.IMPORTANCEThe physiological consequences of disrupting conserved envelope systems can vary with the conditions in which bacteria grow. In <i>Acinetobacter baumannii</i>, loss of Tol-Pal has little effect on population growth under routine laboratory conditions but modestly compromises outer membrane barrier robustness, whereas specific environmental and host-associated conditions reveal additional defects in cell division organization and bacterial fitness. These findings highlight how environmental context shapes the physiological consequences of Tol-Pal deficiency and provide a framework for understanding why the contribution of this conserved envelope system differs among gram-negative bacteria.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0028926"},"PeriodicalIF":3.8,"publicationDate":"2026-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149168963","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":"EndD mediates butyrate-dependent toxin release and sporulation in <i>Clostridioides difficile</i>.","authors":"Horia A Dobrila, Henrieta Licha, Andrew J Hryckowian","doi":"10.1128/jb.00341-26","DOIUrl":"10.1128/jb.00341-26","url":null,"abstract":"<p><p><i>Clostridioides difficile</i> is an urgent threat to human health. Current treatments for <i>C. difficile</i> infections (CDIs) are antibiotics and microbiome restoration therapy (MRT) for recurrent cases. However, antibiotics contribute to antibiotic resistance and recurrent CDIs, and the long-term sustainability and accessibility of MRTs remain to be determined. Since a dysbiotic gut microbiome is the primary risk factor for CDI, a better understanding of the interactions between <i>C. difficile</i>, the microbiome, and the host will aid development of treatments with improved precision. Emerging evidence supports that butyrate, a prominent end product of gut microbiome metabolism, is a key determinant of <i>C. difficile</i> pathogenesis. Notably, <i>C. difficile</i> releases more of its toxins (TcdA and TcdB) in butyrate-rich environments. Here, we demonstrate that butyrate-dependent toxin release is not driven by two previously characterized modes of toxin release (e.g., TcdE-dependent secretion or Cwp19-dependent autolysis). Instead, butyrate enhances the expression of a broadly conserved endolysin (EndD), which is responsible for butyrate-dependent toxin release. We additionally demonstrate that <i>endD</i>-dependent toxin release does not universally occur under all growth conditions, that its expression is dependent on the late-stage sporulation sigma factor SigK, and that <i>endD</i> enhances butyrate-dependent sporulation. Overall, our findings provide deeper insight into butyrate-dependent effects on <i>C. difficile</i> pathogenesis and set the stage for future work to better understand the molecular and genetic underpinnings of <i>endD</i> regulation.IMPORTANCE<i>Clostridioides difficile</i> is a leading cause of infectious diarrhea. The gut microbiome-derived short-chain fatty acid butyrate triggers <i>C. difficile</i> to release its major virulence factors, toxins TcdA and TcdB. Here, we show that butyrate-dependent toxin release is independent of classical secretion or autolytic pathways and is instead mediated by EndD, an endolysin broadly conserved among <i>C. difficile</i> clinical isolates. We also demonstrate that <i>endD</i> expression is governed by the sporulation factor SigK and enhances sporulation, directly linking transmission and virulence. Uncovering how <i>C. difficile</i> couples metabolic sensing to EndD-mediated toxin release and sporulation advances our understanding of pathogen-microbiome interactions and highlights potential targets for non-antibiotic therapeutics.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0034126"},"PeriodicalIF":3.8,"publicationDate":"2026-10-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149109923","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":"Activation of the MprBA two-component system in <i>Mycobacterium smegmatis</i> under acidic and respiration-inhibitory conditions and crosstalk between MprA and KdpD.","authors":"Yun-Kyung Kim, Ye-Jin Lee, Jeong-Il Oh","doi":"10.1128/jb.00361-26","DOIUrl":"https://doi.org/10.1128/jb.00361-26","url":null,"abstract":"<p><p>The MprBA two-component system (TCS) plays a critical role in <i>Mycobacterium tuberculosis</i> persistence and forms a signaling pathway with the alternative sigma factors SigE and SigB. Here, we demonstrate that the MprBA-SigE-SigB signaling pathway is activated in <i>Mycobacterium smegmatis</i> under multiple stress conditions associated with respiratory inhibition, including genetic inactivation of the <i>aa</i>₃ cytochrome <i>c</i> oxidase, treatment with the <i>bcc</i>₁ complex inhibitor Q203, hypoxia, high ionic strength, and acidic pH. Strikingly, acidic pH elicited the strongest activation of MprA-dependent <i>sigE</i> expression, suggesting that MprB integrates multiple stress signals beyond respiratory dysfunction. Deletion of <i>mprB</i> resulted in constitutive activation of MprA rather than inactivation, as evidenced by elevated <i>sigE</i> expression, increased MprA phosphorylation, and enhanced rifampicin resistance in an <i>mprB</i> mutant. Using CRISPRi-mediated repression and genetic deletion, we identified the KdpD histidine kinase, a component of the potassium homeostasis KdpDE TCS, as required for phosphorylating and activating MprA in the absence of MprB. These findings reveal unexpected crosstalk between KdpD and MprA. Expression of a truncated MprB lacking the N-terminal sensory domain abolished <i>sigE</i> expression under both neutral and acidic conditions, indicating that this domain is essential for sensing environmental signals and that the truncated protein behaves as a phosphatase-dominant form under the conditions tested. Growth analysis revealed that MprA, SigE, and SigB are required for optimal growth under acidic conditions, demonstrating the importance of the MprBA-SigE-SigB pathway for survival of <i>M. smegmatis</i> under acidic stress.IMPORTANCEThe MprBA TCS contributes to mycobacterial stress adaptation and persistence by regulating SigE- and SigB-mediated stress response pathways. Here, we show that the MprBA TCS is activated under respiration-inhibitory and acidic conditions in <i>Mycobacterium smegmatis</i>, suggesting that this pathway responds to environmental cues relevant to host infection. We also identify an unexpected regulatory relationship between the MprBA and KdpDE systems: in the absence of MprB, MprA can be phosphorylated and activated by the noncognate histidine kinase KdpD. These findings suggest that MprB phosphatase activity is critical for maintaining low basal MprA activity and preventing inappropriate KdpD-mediated activation under non-stress conditions.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0036126"},"PeriodicalIF":3.8,"publicationDate":"2026-10-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149110101","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":"Acquisition of novel arrays via horizontal gene transfer rewires CRISPR-mediated defense in <i>Pseudomonas aeruginosa</i>.","authors":"Robbie Paul P Malaluan, Ron Leonard V Dy","doi":"10.1128/jb.00339-26","DOIUrl":"10.1128/jb.00339-26","url":null,"abstract":"&lt;p&gt;&lt;p&gt;Clustered regularly interspaced short palindromic repeat (CRISPR)-associated (Cas) systems form the adaptive immunity of prokaryotes, conferring sequence-specific protection against genetic parasites. Here, we functionally characterized the type I-F CRISPR-Cas system of &lt;i&gt;Pseudomonas aeruginosa&lt;/i&gt; ATCC 10145 (PA10145), which led us to discover the existence of an isolated CRISPR array unique to this system. Its core CRISPR-Cas system is composed of a &lt;i&gt;cas&lt;/i&gt; operon flanked by two divergently organized arrays: CRISPR2 and CRISPR1. Meanwhile, the isolated CRISPR array, CRISPR3, was found ~1.3 million bp away from &lt;i&gt;cas&lt;/i&gt;. The &lt;i&gt;cas&lt;/i&gt; and three CRISPR arrays together function toward adaptive immunity, eliminating plasmids engineered with protospacer targets. If plasmids possessed an intact protospacer adjacent motif (PAM), hyperactive adaptation was stimulated in all CRISPR arrays of PA10145, whereas minimal to no adaptation was observed when the PAM was mutated. Spacer acquisition via interference-driven adaptation proceeds through strand-biased priming in PA10145. Interestingly, the isolated CRISPR3 and &lt;i&gt;cas&lt;/i&gt;-adjacent CRISPR2 have nearly identical leader sequences, with only 3 bp mismatches. Of the 1,196 &lt;i&gt;P. aeruginosa&lt;/i&gt; genomes analyzed, all 281 isolated arrays only occur as type I-F with similarly matching leaders to CRISPR2. Integrative conjugative elements and prophages only associate with CRISPR2 and CRISPR3, suggesting that isolated arrays might have originated from recombination events involving CRISPR2 as facilitated by these highly transmissible mobile genetic elements. Tracing evolutionary trajectories of the isolated CRISPR3 relative to &lt;i&gt;cas&lt;/i&gt;-adjacent arrays revealed that CRISPR3 is horizontally transferred across &lt;i&gt;P. aeruginosa&lt;/i&gt; genomes. Taken together, these results implicate the role of horizontally acquired isolated arrays in CRISPR-mediated pan-immunity as gateways to mobilize genetic memories.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Importance: &lt;/strong&gt;Clustered regularly interspaced short palindromic repeat (CRISPR) arrays are typically located adjacent to &lt;i&gt;cas&lt;/i&gt; genes, constituting the adaptive immune system. However, a substantial subset of CRISPR arrays, called isolated arrays, is found distantly located from their cognate &lt;i&gt;cas&lt;/i&gt; operons. Despite their prevalence, the functional significance and evolutionary implications of isolated arrays have remained poorly understood. Here, we show that isolated arrays are active components of type I-F CRISPR-Cas systems in &lt;i&gt;Pseudomonas aeruginosa&lt;/i&gt;. These arrays are continuously updated through hyperactive strand-biased primed adaptation and are transferred horizontally across &lt;i&gt;P. aeruginosa&lt;/i&gt;, acting as conduits of immunological memory and proponents of CRISPR-mediated pan-immunity. We posit that bacterial populations mobilize these isolated arrays to maintain transferable memory in the pangenome while remaining compatible with ongoing horizontal gene transfer.","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0033926"},"PeriodicalIF":3.8,"publicationDate":"2026-10-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149110076","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":"Efficient septum formation is essential for chromosome segregation in <i>Bacillus subtilis</i> when SMC function is impaired.","authors":"Ngoc Khanh Lai, Laura C Lastra, Kehinde O Adebiyi, David Z Rudner, Stephen C Jacobson, Daniel B Kearns, Xindan Wang","doi":"10.1128/jb.00345-26","DOIUrl":"10.1128/jb.00345-26","url":null,"abstract":"<p><p>Structural maintenance of chromosomes (SMC) complexes play conserved roles in chromosome organization, segregation, and repair in all domains of life. In <i>Bacillus subtilis</i>, SMC is required for the segregation of newly replicated origins. To investigate whether other proteins function with SMC in this process, we performed a synthetic lethal screen with an <i>smc</i> hypomorphic allele (<i>smc</i>*) that is mildly defective in chromosome segregation. In addition to recovering previously reported genetic interactions of <i>smc</i> with <i>parB</i> and <i>spoIIIE</i>, our screen identified <i>minJ</i> and <i>divIVA</i> as essential in the <i>smc*</i> background. We show that the synthetic lethality between <i>smc*</i> and <i>∆minJ</i> or <i>∆divIVA</i> arises from defects in segregating the replication terminus. Importantly, deletion of <i>minD</i>, which suppresses the cell division defects of <i>∆minJ</i> and <i>∆divIVA</i>, restored terminus segregation and viability in the <i>smc*</i> background. These findings support a model in which proper septum formation promotes chromosome terminus resolution and segregation by enabling SpoIIIE-mediated DNA clearance from the division septum during cytokinesis. These findings highlight the interdependence between chromosome segregation and cell division.IMPORTANCEThe SMC complex plays a central role in chromosome organization and segregation in <i>Bacillus subtilis</i>, but the cellular functions that become important when SMC activity is reduced are not well understood. Using a hypomorphic <i>smc</i> allele, we discovered that mutations affecting cell division become essential when chromosome organization and segregation are impaired. Our findings support a model in which efficient septum formation enables proper localization of the SpoIIIE DNA translocase, which in turn resolves and segregates the chromosome terminus region. These results highlight the critical role of cell division in supporting chromosome segregation.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0034526"},"PeriodicalIF":3.8,"publicationDate":"2026-10-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149109845","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":"Effects of sporulation in an extremely poor medium on <i>Bacillus subtilis</i> spore resistance, germination, and physical properties.","authors":"Caroline Burkott, Ayoni Chakraborty, William J Bannon Iv, Jane Setlow Anetsky, James Wicander, George Korza, Holly L Maschenik, Yongqing Li, Peter Setlow","doi":"10.1128/jb.00383-26","DOIUrl":"https://doi.org/10.1128/jb.00383-26","url":null,"abstract":"<p><p>Spores of <i>Bacillus</i> species are metabolically dormant and resistant to many agents but can come back to life in germination triggered by a variety of small molecules; these spore properties vary depending on the conditions and media for spore formation. In the current work, we have compared the properties of <i>Bacillus subtilis</i> spores made in a rich medium and an extremely poor medium. Notably, spores made in the poor liquid medium had lowered resistance to wet heat and somewhat lowered resistance to hydrogen peroxide and formaldehyde. Spores made in the poor liquid medium also have an inner membrane (IM) that is more permeable and fluid compared to the IM in spores made in a rich medium. The poor liquid medium spores also germinated slower than the rich medium spores with several germinant receptor (GR) germinants but faster with the non-GR-dependent germinant dodecylamine. While the reasons for the latter differences are likely the more fluid and permeable IM in the poor medium spores, there were minimal, if any, differences between rich and poor medium spores in their levels of core water or CaDPA, two compounds that alone have major effects on spore resistance properties. These findings provide new information on the resistance and germination properties of spores of <i>B. subtilis</i>.IMPORTANCESpores of various <i>Bacillus</i> species can cause adverse effects such as food spoilage and some human diseases due to their resistance properties and ability to \"come back to life\" in spore germination. The reason for these effects has been commonly studied using spores prepared in relatively rich media, and there is a large body of literature on this. However, there have been minimal, if any, studies using spores prepared in an extremely poor medium, as was done in the current work. We believe that the findings in this work provide new insight into mechanisms of spore resistance and their germination.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0038326"},"PeriodicalIF":3.8,"publicationDate":"2026-10-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149109505","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":"Loss of RafE impairs raffinose utilization and increases early pneumococcal burden in mice.","authors":"Kate P Whyte, Mark van der Linden, James C Paton, Claudia Trappetti, Anna E Sheppard, Erin B Brazel","doi":"10.1128/jb.00330-26","DOIUrl":"https://doi.org/10.1128/jb.00330-26","url":null,"abstract":"<p><p><i>Streptococcus pneumoniae</i> (the pneumococcus) is one of the most common bacterial causes of middle ear infections (otitis media) in children. These infections are highly prevalent but can be persistent and challenging to treat. The pneumococcus is a highly genetically diverse organism, but the precise molecular factors that drive infection of the ear are not fully understood. Bacterial metabolic capacity is known to play an important role in infection. Here, we explored the metabolic capacity of two serotype 3 isolates of <i>S. pneumoniae</i> obtained from the middle ear of children with otitis media. Serotype 3 is a clinically relevant serotype of concern due to its inadequate control despite its inclusion in pneumococcal conjugate vaccines. We identified one strain as unable to metabolize raffinose, and by coupling genomic and phenotypic methods, we showed that this metabolic defect was likely due to a premature stop codon in the gene encoding the raffinose-family oligosaccharide utilization system ABC transporter substrate-binding protein (<i>rafE</i>). Using a <i>S. pneumoniae</i> D39 serotype 2 strain as a model, we showed that construction of a <i>rafE</i> deletion or introduction of the variant gene resulted in an increase in the number of pneumococci in the ears of mice, suggesting that this may promote transit to, or survival at, this site. This work provides further evidence of variation at the raffinose utilization locus in pneumococci and an association with distinct virulence phenotypes. Together, this aids our understanding of these infections and may have implications for the design of new therapies and vaccines.IMPORTANCE<i>Streptococcus pneumoniae</i> is a bacterium that lives in the nose of healthy people but can cause a range of infections in the lungs, ears, brain, and blood. In this study, we explore how <i>S. pneumoniae</i> acquires nutrients and proliferates inside different sites of the body. We found that nutrient uptake pathways can differ between strains, and this changes how they infect different sites. The significance of our research is in understanding how these bacteria survive in different parts of the body, which is important for developing new ways of preventing or treating disease.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0033026"},"PeriodicalIF":3.8,"publicationDate":"2026-10-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149110039","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":"Protein secretion by the type IV pilus machinery in <i>Francisella tularensis</i>.","authors":"Angela DeRosa, P Todd Benziger, Vinaya Sampath, Erik J Kopping, Huiyeon Kim, David G Thanassi","doi":"10.1128/jb.00253-26","DOIUrl":"10.1128/jb.00253-26","url":null,"abstract":"<p><p><i>Francisella tularensis</i> is a highly virulent, gram-negative bacterial pathogen that causes the zoonotic disease tularemia. <i>F. tularensis</i> infects a variety of host cells and replicates intracellularly while evading and interfering with host immune responses. The molecular mechanisms that facilitate the intracellular replication and virulence of <i>F. tularensis</i> are poorly understood. The <i>Francisella</i> genome contains a set of <i>pil</i> genes that code for the assembly of surface fibers termed type IV pili (T4P). T4P are major bacterial virulence determinants, but the function of the <i>pil</i> system during <i>F. tularensis</i> infection and intracellular growth is unclear. T4P are closely related to the type II secretion pathway, and the <i>pil</i> system of a related <i>Francisella</i> species, <i>F. novicida</i>, was shown to function in protein secretion as well as pilus assembly. To identify proteins secreted by <i>F. tularensis</i>, we analyzed the <i>F. tularensis</i> Live Vaccine Strain (LVS) using bio-orthogonal noncanonical amino acid tagging (BONCAT). Using BONCAT in conjunction with proteomics, we identified candidate proteins secreted by the wild-type LVS, as well as candidate proteins whose extracellular abundance decreased in the absence of the PilF ATPase or the PilE4 pilus subunit. Using epitope tagging of selected candidates, we validated T4P-mediated secretion of the ChiA and ChiD chitinases and the KatG catalase by the LVS. These results further our understanding of the <i>pil</i> system and protein secretion pathways in <i>F. tularensis</i>.IMPORTANCE<i>Francisella tularensis</i> is a highly virulent gram-negative bacterial pathogen and the causative agent of tularemia. <i>F. tularensis</i> lacks secretion systems utilized by other intracellular bacterial pathogens but contains <i>pil</i> genes that encode for type IV pili (T4P) and may also function in protein secretion. T4P are observed on the surface of all <i>Francisella</i> spp., but <i>pil</i>-mediated protein secretion has only been reported for <i>F. novicida</i>, which is not normally pathogenic in humans. In this study, we used bio-orthogonal noncanonical amino acid tagging to identify proteins secreted by <i>F. tularensis</i>, for which there is limited information. We demonstrate that the <i>F. tularensis pil</i> system is capable of protein secretion and validate T4P-mediated secretion of the ChiA and ChiD chitinases and the KatG catalase. These results will facilitate investigation of <i>Francisella</i> virulence mechanisms and may provide targets for therapeutic intervention.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0025326"},"PeriodicalIF":3.8,"publicationDate":"2026-10-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149110026","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 lysine acetyltransferase Rv0998 coordinates transcriptional and metabolic adaptation of <i>Mycobacterium tuberculosis</i> to acidic pH.","authors":"Yi Liu, Nadia Fernandes, Valwynne Faulkner, Richard Williams, Eachan Johnson, Sandhya Visweswariah, Brian D Robertson, Gerald Larrouy-Maumus","doi":"10.1128/jb.00408-26","DOIUrl":"https://doi.org/10.1128/jb.00408-26","url":null,"abstract":"<p><p><i>Mycobacterium tuberculosis</i> (Mtb) survives host defenses by adapting to host conditions, including acid stress, during infection. A critical survival strategy involves pH homeostasis, mediated by complex signaling systems that regulate metabolic reprogramming and stress responses. While the lysine acetyltransferase Rv0998 is known to support Mtb hypoxia adaptation and metabolic flexibility, its role in acid stress remains unexplored. Here, we investigated the consequences of <i>rv0998</i> deletion in 7H9 with glucose as the major carbon source. RNA-seq analysis showed that loss of Rv0998 altered the transcriptional response to acidic pH, including changes in the DosR regulon and <i>pfkB</i>/Rv2029c. Stable isotope tracing with [U-¹³C₆]-glucose also showed reduced fractional ¹³C labeling across central carbon metabolites in the <i>rv0998</i> mutant, with the largest decrease at acidic pH observed in upper glycolytic and connected hexose-phosphate intermediates. Growth and glucose-labeling phenotypes of <i>dosR</i> and <i>pfkB</i> mutants provided focused examples of stress-responsive and carbon-metabolic processes associated with the broader Rv0998 response. These findings indicate that Rv0998 contributes to coordinated transcriptional and metabolic adaptation of Mtb to acidic pH, and support further investigation of how stress-responsive regulatory programs are coupled to carbon metabolism during acid adaptation.IMPORTANCE<i>Mycobacterium tuberculosis</i> (Mtb) persists in host environments that are both acidic and nutritionally variable, but the regulatory processes that connect these stresses to metabolism remain incompletely understood. We show that loss of the lysine acetyltransferase Rv0998 impairs growth at acidic pH when glucose is the major carbon source, and is accompanied by broad changes in gene expression and incorporation of glucose-derived carbon into central metabolites. The phenotype is not apparent when glycerol is also present, indicating that the response depends on carbon-source context. These findings identify Rv0998 as a contributor to the coordination of acid-stress adaptation and central carbon metabolism in Mtb, the bacterium that causes tuberculosis.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0040826"},"PeriodicalIF":3.8,"publicationDate":"2026-10-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149110033","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 role of toxin-antitoxin systems in <i>Helicobacter pylori</i> adaptability.","authors":"Juan D Romero-Carpio, Luis D Chacón-Loría, Silvia Molina-Castro, Bradd Mendoza-Guido","doi":"10.1128/jb.00166-26","DOIUrl":"10.1128/jb.00166-26","url":null,"abstract":"<p><p>Toxin-antitoxin (TA) systems are genetic modules widely distributed across bacterial chromosomes and mobile genetic elements. Initially described as plasmid addiction systems that ensure vertical inheritance through post-segregational killing, they are now recognized as versatile regulators of bacterial adaptability. In <i>Helicobacter pylori</i>, a gastric pathogen infecting nearly half of the global population, multiple TA systems have been experimentally validated, including type I RNA-RNA modules and type II protein-protein pairs. These systems contribute to growth arrest, morphological transition from spiral to coccoid forms, biofilm formation, intracellular survival, and responses to environmental stressors, such as oxidative stress, metal availability, and antibiotic exposure. Type I AapA/IsoA modules have been linked to membrane targeting and dormancy induction, whereas certain Vap-like type II toxins act as ribonucleases and likely contribute to colonization and persistence during infection. Although hundreds of putative TA loci have been identified through bioinformatic analyses, only a small fraction has been functionally characterized, highlighting substantial knowledge gaps. This minireview summarizes experimentally validated TA systems in <i>H. pylori</i>, discusses predicted candidates, and examines their potential roles in pathogen adaptability, emphasizing their relevance to <i>H. pylori</i> persistence and pathogenicity.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0016626"},"PeriodicalIF":3.8,"publicationDate":"2026-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13584709/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148712601","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}