Journal of Bacteriology最新文献

{"title":"Genome-wide analysis of <i>Enterococcus faecalis</i> genes that facilitate interspecies competition with <i>Lactobacillus crispatus</i>.","authors":"Ling Ning Lam, Kathryn E Savage, Camille N Shakir, José A Lemos","doi":"10.1128/jb.00438-24","DOIUrl":"10.1128/jb.00438-24","url":null,"abstract":"<p><p>Enterococci are opportunistic pathogens notorious for causing a variety of infections. While both <i>Enterococcus faecalis</i> and <i>Lactobacillus crispatus</i> are commensal residents of the vaginal tract, the molecular mechanisms that enable <i>E. faecalis</i> to take advantage of a vaginal biome with lower counts of lactobacilli to colonize the vaginal tract and induce aerobic vaginitis remain unknown. Here, we show that <i>L. crispatus</i> eradicates <i>E. faecalis</i> in a contact-independent manner. Using transposon sequencing to identify <i>E. faecalis</i> OG1RF transposon (Tn) mutants that are either under-represented or over-represented when co-cultured with <i>L. crispatus</i>, we found that Tn mutants with disruption in the <i>dltABCD</i> operon, that encodes the proteins responsible for the D-alanylation of teichoic acids, and <i>OG1RF_11697</i> encoding for an uncharacterized hypothetical protein are more susceptible to killing by <i>L. crispatus</i>. Inversely, Tn mutants with disruption in <i>ldh1,</i> which encodes for L-lactate dehydrogenase, are more resistant to <i>L. crispatu</i>s killing. Using the <i>Galleria mellonella</i> infection model, we show that co-injection of <i>L. crispatus</i> with <i>E. faecalis</i> OG1RF enhances larvae survival while this <i>L. crispatus</i>-mediated protection was lost in larvae co-infected with either <i>L. crispatus</i> and <i>E. faecalis</i>Δ<i>ldh1</i> or Δ<i>ldh1</i>Δ<i>ldh2</i> strains. Last, using RNA sequencing to identify <i>E. faecalis</i> genes that are differently expressed in the presence of <i>L. crispatus</i>, we found major changes in the expression of genes associated with glycerophospholipid metabolism, central metabolism, and general stress responses. The findings in this study provide insights into how <i>E. faecalis</i> mitigate assaults by <i>L. crispatus</i>.IMPORTANCE<i>Enterococcus faecalis</i> is an opportunistic pathogen notorious for causing a multitude of infections. As vaginal commensals, <i>E. faecalis</i> must interact with <i>Lactobacillus crispatus</i>, but how <i>E. faecalis</i> overcomes or mitigate assaults by <i>L. crispatus</i> killing remains unknown. We show that <i>L. crispatus</i> eradicates <i>E. faecalis</i> temporally in a contact-independent manner. Using high-throughput molecular approaches, we identified genetic determinants that enable <i>E. faecalis</i> to compete with <i>L. crispatus</i>. This study represents an important first step for the identification of adaptive genetic traits required for enterococci to tolerate assaults by lactobacilli.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0043824"},"PeriodicalIF":2.7,"publicationDate":"2025-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11925238/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143189394","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}

{"title":"On the role of the sorting platform in hierarchical type III secretion regulation in enteropathogenic <i>Escherichia coli</i>.","authors":"Arely Marcos-Vilchis, Norma Espinosa, Adrián F Alvarez, José L Puente, J Eduardo Soto, Bertha González-Pedrajo","doi":"10.1128/jb.00446-24","DOIUrl":"10.1128/jb.00446-24","url":null,"abstract":"<p><p>The virulence of enteropathogenic <i>Escherichia coli</i> (EPEC) depends on a type III secretion system (T3SS), a membrane-spanning apparatus that injects effector proteins into the cytoplasm of target enterocytes. The T3SS, or injectisome, is a self-assembled nanomachine whose biogenesis and function rely on the ordered secretion of three distinct categories of proteins: early, middle, and late type III substrates. In EPEC, this hierarchical secretion is assisted by several cytosolic protein complexes at the base of the injectisome. Among these, the sorting platform is involved in the recognition and sequential loading of the different classes of T3-substrates. In addition, a heterotrimeric gatekeeper complex, also known as a molecular switch, operates in concert with components of the T3SS export apparatus to guarantee the delivery of middle substrates prior to late substrate secretion. In this study, we showed that the sorting platform is differentially required for the secretion of distinct categories of substrates. Moreover, we demonstrated a cooperative interplay and protein-protein interactions between the sorting platform and the gatekeeper complex for proper middle and late substrate docking and secretion. Overall, our results provide new insights into the intricate molecular mechanisms that regulate protein secretion hierarchy during T3SS assembly.IMPORTANCEEnteropathogenic <i>Escherichia coli</i> employs a type III secretion system to deliver virulence proteins directly into host cells, disrupting multiple cellular processes to promote infection. This multiprotein system assembles in a precise stepwise manner, with specific proteins being recruited and secreted at distinct stages. The sorting platform and the gatekeeper complex play critical roles in regulating this process, but their cooperative mechanism has not been fully elucidated. Here, we reveal a novel functional interaction between these two components, which is critical for hierarchical substrate recognition and secretion. These findings advance our understanding of the molecular mechanisms underlying bacterial virulence and suggest new potential targets for antimicrobial strategies aimed at disrupting T3SS function.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0044624"},"PeriodicalIF":2.7,"publicationDate":"2025-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11925242/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143542075","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}

{"title":"Characterization of a cytokinin-binding protein locus in <i>Mycobacterium tuberculosis</i>.","authors":"Jin Hee Yoo, Cristina Santarossa, Audrey Thomas, Damian Ekiert, K Heran Darwin","doi":"10.1128/jb.00003-25","DOIUrl":"10.1128/jb.00003-25","url":null,"abstract":"<p><p>Cytokinins are adenine-based hormones that have been well-characterized in plants but are also made by bacteria, including the human-exclusive pathogen <i>Mycobacterium tuberculosis</i>. Like plants, <i>M. tuberculosis</i> uses cytokinins to regulate gene expression. We previously established that cytokinin overaccumulation in <i>M. tuberculosis</i> results in a buildup of aldehydes produced during cytokinin breakdown. In plants, dedicated enzymes called cytokinin oxidases convert cytokinins into adenine and various aldehydes. Proteasome degradation-deficient <i>M. tuberculosis</i>, which cannot degrade the cytokinin-producing enzyme Log, accumulates several cytokinins and at least one cytokinin-associated aldehyde, resulting in increased sensitivity to nitric oxide and copper. We therefore hypothesized that <i>M. tuberculosis</i> encodes one or more cytokinin oxidases, and disruption of this enzyme might restore resistance to nitric oxide and copper in a proteasome-defective strain. Using a homology-based search, we identified Rv3719 as a protein with high similarity to a plant cytokinin oxidase. Deletion of this gene, however, did not restore nitric oxide or copper resistance to a degradation-defective mutant. Instead, we observed increased copper sensitivity when Rv3719 was deleted from either wild-type or proteasome-defective strains. Finally, we characterized Rv3718c, a protein encoded adjacent to Rv3719, and found that it bound a cytokinin with high specificity. Collectively, these data support a role for cytokinin activity in <i>M. tuberculosis</i> physiology that remains to be further elucidated.IMPORTANCENumerous bacterial species encode cytokinin-producing enzymes, the functions of which are almost completely unknown. This work contributes new knowledge to the cytokinin field for bacteria and reveals further conservation of cytokinin-associated proteins between plants and prokaryotes.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0000325"},"PeriodicalIF":2.7,"publicationDate":"2025-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11925245/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143515572","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}

{"title":"The <i>Salmonella</i> pathogenicity island 1-encoded small RNA InvR mediates post-transcriptional feedback control of the activator HilA in <i>Salmonella</i>.","authors":"Yutong Hou, Kyungsub Kim, Fatih Cakar, Yekaterina A Golubeva, James M Slauch, Carin K Vanderpool","doi":"10.1128/jb.00491-24","DOIUrl":"10.1128/jb.00491-24","url":null,"abstract":"<p><p><i>Salmonella</i> Pathogenicity Island 1 (SPI1) encodes a Type-3 secretion system (T3SS) essential for <i>Salmonella</i> invasion of intestinal epithelial cells. Many environmental and regulatory signals control SPI1 gene expression, but in most cases, the molecular mechanisms remain unclear. Many regulatory signals control SPI1 at a post-transcriptional level, and we have identified a number of small RNAs (sRNAs) that control the SPI1 regulatory circuit. The transcriptional regulator HilA activates the expression of the genes encoding the SPI1 T3SS structural and primary effector proteins. Transcription of <i>hilA</i> is controlled by the AraC-like proteins HilD, HilC, and RtsA. The <i>hilA</i> mRNA 5' untranslated region (UTR) is ~350 nucleotides in length and binds the RNA chaperone Hfq, suggesting it is a likely target for sRNA-mediated regulation. We used rGRIL-seq (reverse global sRNA target identification by ligation and sequencing) to identify sRNAs that bind to the <i>hilA</i> 5' UTR. The rGRIL-seq data, along with genetic analyses, demonstrate the SPI1-encoded sRNA <u>inv</u>asion gene-associated <u>R</u>NA (InvR) base pairs at a site overlapping the <i>hilA</i> ribosome binding site. HilD and HilC activate both <i>invR</i> and <i>hilA</i>. InvR, in turn, negatively regulates the translation of the <i>hilA</i> mRNA. Thus, the SPI1-encoded sRNA InvR acts as a negative feedback regulator of SPI1 expression. Our results suggest that InvR acts to fine-tune SPI1 expression and prevents overactivation of <i>hilA</i> expression, highlighting the complexity of sRNA regulatory inputs controlling SPI1 and <i>Salmonella</i> virulence.</p><p><strong>Importance: </strong><i>Salmonella</i> Typhimurium infections pose a significant public health concern, leading to illnesses that range from mild gastroenteritis to severe systemic infection. Infection requires a complex apparatus that the bacterium uses to invade the intestinal epithelium. Understanding how <i>Salmonella</i> regulates this system is essential for addressing these infections effectively. Here, we show that the small RNA (sRNA) InvR imposes a negative feedback regulation on the expression of the invasion system. This work underscores the role of sRNAs in <i>Salmonella</i>'s complex regulatory network, offering new insights into how these molecules contribute to bacterial adaptation and pathogenesis.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0049124"},"PeriodicalIF":2.7,"publicationDate":"2025-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11925239/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143515661","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}

{"title":"<i>Clostridioides difficile</i> infection study models and prospectives for probing the microbe-host interface.","authors":"Tatiana Zvonareva, David S Courson, Erin B Purcell","doi":"10.1128/jb.00407-24","DOIUrl":"10.1128/jb.00407-24","url":null,"abstract":"<p><p><i>Clostridioides difficile</i> infection (CDI) is an urgent public health threat with a high rate of recurrence and limited treatment options. <i>In vivo</i> models have been indispensable in understanding CDI pathophysiology and establishing treatment protocols and continue to be essential in pre-clinal testing. More importantly, <i>in vivo</i> models offer the opportunity to probe the complex systemic host response to the microbe, which is impossible to recapitulate <i>in vitro</i>. Nonetheless, constraints related to the availability of animal models, cost, ethical considerations, and regulatory control limit their accessibility for basic research. Furthermore, physiological and habitual divergences between animal models and humans often result in poor translatability to human patients. In addition to being more accessible, <i>in vitro</i> CDI models offer more control over experimental parameters and allow dynamic analysis of early infection. <i>In vitro</i> fermentation offers models for probing microbe-microbe and microbe-microbiome interactions, while continuous multi-stage platforms allow opportunities to study <i>C. difficile</i> pathophysiology and treatment in context with human-derived microbiota. However, these platforms are not suitable for probing the host-pathogen interface, leaving the challenge of modeling early CDI unanswered. As a result, alternative <i>in vitro</i> co-culture platforms are being developed. This review evaluates the strengths and weaknesses of each approach, as well as future directions for <i>C. difficile</i> research.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0040724"},"PeriodicalIF":2.7,"publicationDate":"2025-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11925243/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143255681","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}

{"title":"Not just passengers: effectors contribute to the assembly of the type VI secretion system as structural building blocks.","authors":"Sherina Dyrma, Tong-Tong Pei, Xiaoye Liang, Tao Dong","doi":"10.1128/jb.00455-24","DOIUrl":"10.1128/jb.00455-24","url":null,"abstract":"<p><p>Protein secretion systems are critical macromolecular machines employed by bacteria to interact with diverse environments and hosts during their life cycle. Cytosolically produced protein effectors are translocated across at least one membrane to the outside of the cells or directly into target cells. In most secretion systems, these effectors are mere passengers in unfolded or folded states. However, the type VI secretion system (T6SS) stands out as a powerful contractile device that requires some of its effectors as structural components. This review aims to provide an updated view of the diverse functions of effectors, especially focusing on their roles in T6SS assembly, the implications for T6SS engineering, and the potential of recently developed T6SS models to study effector-T6SS association.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0045524"},"PeriodicalIF":2.7,"publicationDate":"2025-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11925235/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143189467","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}

{"title":"<i>Borrelia burgdorferi</i> loses essential genetic elements and cell proliferative potential during stationary phase in culture but not in the tick vector.","authors":"Jessica Zhang, Constantin N Takacs, Joshua W McCausland, Elizabeth A Mueller, Jeline Buron, Yashna Thappeta, Jenny Wachter, Patricia A Rosa, Christine Jacobs-Wagner","doi":"10.1128/jb.00457-24","DOIUrl":"10.1128/jb.00457-24","url":null,"abstract":"<p><p>The Lyme disease agent <i>Borrelia burgdorferi</i> is a polyploid bacterium with a segmented genome in which both the chromosome and over 20 distinct plasmids are present in multiple copies per cell. This pathogen can survive for at least 9 months in its tick vector in an apparent dormant state between blood meals, without losing cell proliferative capability when re-exposed to nutrients. Cultivated <i>B. burgdorferi</i> cells grown to stationary phase or resuspended in nutrient-limited media are often used to study the effects of nutrient deprivation. However, a thorough assessment of the spirochete's ability to recover from nutrient depletion has been lacking. Our study shows that starved <i>B. burgdorferi</i> cultures rapidly lose cell proliferative ability. Loss of genetic elements essential for cell proliferation contributes to the observed proliferative defect in stationary phase. The gradual decline in copies of genetic elements is not perfectly synchronized between chromosomes and plasmids, generating cells that harbor one or more copies of the essential chromosome but lack all copies of one or more non-essential plasmids. This phenomenon likely contributes to the well-documented issue of plasmid loss during <i>in vitro</i> cultivation of <i>B. burgdorferi</i>. In contrast, <i>B. burgdorferi</i> cells from ticks starved for 14 months showed no evidence of reduced cell proliferative ability or plasmid loss. Beyond their practical implications for studying <i>B. burgdorferi</i>, these findings suggest that the midgut of the tick vector offers a unique environment that supports the maintenance of <i>B. burgdorferi</i>'s segmented genome and cell proliferative potential during periods of tick fasting.IMPORTANCE<i>Borrelia burgdorferi</i> causes Lyme disease, a prevalent tick-borne illness. <i>B. burgdorferi</i> must survive long periods (months to a year) of apparent dormancy in the midgut of the tick vector between blood meals. Resilience to starvation is a common trait among bacteria. However, this study reveals that, in laboratory cultures, <i>B. burgdorferi</i> poorly endures starvation and rapidly loses viability. This decline is linked to a gradual loss of genetic elements required for cell proliferation. These results suggest that the persistence of <i>B. burgdorferi</i> in nature is likely shaped more by unique environmental conditions in the midgut of the tick vector than by an innate ability of this bacterium to endure nutrient deprivation.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0045724"},"PeriodicalIF":2.7,"publicationDate":"2025-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11925233/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143414277","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}

{"title":"A novel regulation on the developmental checkpoint protein Sda that controls sporulation and biofilm formation in <i>Bacillus subtilis</i>.","authors":"Yinghao He, Yuxuan Qin, Jennifer Greenwich, Samantha Balaban, Migue Van Louis Darcera, Kevin Gozzi, Yunrong Chai","doi":"10.1128/jb.00210-24","DOIUrl":"10.1128/jb.00210-24","url":null,"abstract":"<p><p>Biofilm formation by <i>Bacillus subtilis</i> is triggered by an unusually simple environmental sensing mechanism. Certain serine codons, the four TCN codons (N for A, T, C, or G), in the gene for the biofilm repressor SinR caused lowered SinR translation and subsequent biofilm induction during transition from exponential to stationary growth. Global ribosome profiling showed that ribosomes pause when translating the four UCN (U for T on the mRNA) serine codons on mRNA, but not the two AGC/AGU serine codons. We proposed a serine codon hierarchy (AGC/AGT vs TCN) in that genes enriched in the TCN serine codons may experience reduced translation efficiency when serine is limited. In this study, we designed an algorithm to score all protein-coding genes in <i>B. subtilis</i> NCIB3610 based on the serine codon hierarchy. We generated a short list of 50 genes that could be subject to regulation by this novel mechanism. We further investigated one such gene from the list, <i>sda</i>, which encodes a developmental checkpoint protein regulating both sporulation and biofilm formation. We showed that synonymously switching the TCN serine codons to AGC in <i>sda</i> led to delayed biofilm formation and sporulation. This engineered strain also outgrew strains with other synonymously substituted <i>sda</i> alleles (TCN) in competition assays for biofilm formation and sporulation. Finally, we showed that the AGC serine codon substitutions in <i>sda</i> elevated the Sda protein levels. This serine codon hierarchy-based novel signaling mechanism could be exploited by bacteria in adapting to stationary phase and regulating important biological processes.</p><p><strong>Importance: </strong>Genome-wide ribosome profiling in <i>Bacillus subtilis</i> shows that under serine limitation, ribosomes pause on the four TCN (N for A, C, G, and T), but not AGC/AGT serine codons, during translation at a global scale. This serine codon hierarchy (AGC/T vs TCN) differentially influences the translation efficiency of genes enriched in certain serine codons. In this study, we designed an algorithm to score all 4,000+ genes in the <i>B. subtilis</i> genome and generated a list of 50 genes that could be subject to this novel serine codon hierarchy-mediated regulation. We further investigated one such gene, <i>sda</i>, encoding a developmental checkpoint protein. We show that <i>sda</i> and cell developments controlled by Sda are also regulated by this novel mechanism.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0021024"},"PeriodicalIF":2.7,"publicationDate":"2025-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11925247/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143390963","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}

{"title":"Quorum sensing LuxR proteins VjbR and BabR jointly regulate <i>Brucella abortus</i> survival during infection.","authors":"Mitchell T Caudill, S Tristan Stoyanof, Clayton C Caswell","doi":"10.1128/jb.00527-24","DOIUrl":"10.1128/jb.00527-24","url":null,"abstract":"<p><p><i>Brucella abortus</i> maintains an <i>N</i>-acetyl homoserine lactone quorum sensing system that consists of two LuxR proteins, VjbR and BabR, as well as two signals, dodecanoyl (C12 AHL) and 3-oxododecanoyl (3-OXO-C12 AHL) homoserine lactone. This system regulates major virulence factors that influence the bacteria's survival during infection. We generated the first strain that lacks both LuxR proteins and found a synergistic interaction for survival in the chronic infection C57BL/6 mouse model. Transcriptomic analyses of the <i>∆vjbR∆babR</i> double-deletion strain, as well as the cognate single-deletion strains, in a rich medium with vehicle control or supplemented with an AHL signal revealed large-scale genetic dysregulation in all conditions. Moreover, the double mutant maintained a limited response to AHL, even in the absence of the LuxR proteins. We additionally found that quorum sensing regulates the denitrification pathway but found no <i>in vitro</i> differences in the ability of quorum sensing deletion strains to clear nitric oxide stress or grow under anoxic denitrifying conditions. Finally, we confirmed that BabR autoregulates its own expression, and that VjbR mildly represses BabR expression. Altogether, these experiments help further characterize the <i>Brucella</i> quorum sensing systems and indicate that further attention should be given to the joint interactions between VjbR and BabR in controlling virulence.IMPORTANCE<i>Brucella abortus</i> is a zoonotic bacterial pathogen that uses its quorum sensing to survive within hosts. This study further characterizes that system and indicates important future lines of inquiry. We found that both quorum sensing proteins, VjbR and BabR, coordinate to maintain survival, as well as document that both quorum sensing systems appear physiologically active.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0052724"},"PeriodicalIF":2.7,"publicationDate":"2025-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11925318/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143515637","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}

{"title":"Sucrose and malic acid in the tobacco plant induce <i>hrp</i> regulon in a phytopathogen <i>Ralstonia pseudosolanacearum</i>.","authors":"Yuzhu Cao, Masayuki Tsuzuki, Akinori Kiba, Yasufumi Hikichi, Yong Zhang, Kouhei Ohnishi","doi":"10.1128/jb.00273-24","DOIUrl":"10.1128/jb.00273-24","url":null,"abstract":"<p><p>Genes encoding a type III secretion system in <i>Ralstonia pseudosolanacearum</i> are regulated by HrpB as an <i>hrp</i> regulon and induced only in plants. This study aimed to identify the plant signals that induce the <i>hrp</i> regulon and confirm the signal recognition mechanism. Signaling molecules that induce <i>hrpB</i> expression were screened using resting cells of the <i>hrpB-lacZ</i> reporter strain. Only the soluble fraction of smashed tobacco seedlings induced <i>hrpB</i> expression. The heated soluble fraction retained its <i>hrpB</i>-inducing activity, indicating that the signaling molecules were not proteins. When the soluble fraction was fractionated into acidic, neutral, and basic components, both the acidic and neutral fractions induced <i>hrpB</i> expression. As neutral compounds, sucrose, glucose, and fructose have been found to induce <i>hrpB</i> expression. Sucrose-induced <i>hrpB</i> expression was greatly reduced in the <i>prhA</i> mutant, indicating that the TonB-dependent receptor PrhA perceives sugars. Among the organic acids found in the acidic fractions, malic acid most efficiently induced <i>hrpB</i> expression, which was reduced by the mutation of a hybrid histidine kinase gene of a two-component system, <i>rsc1598</i>, indicating that Rsc1598 may sense malic acid. We demonstrated direct binding of Rsc1598 to malic acid using isothermal titration calorimetry.IMPORTANCESimilar to other Gram-negative plant pathogens, the type III secretion system (T3SS) is the most important virulence factor in <i>Ralstonia pseudosolanacearum</i>. The genes for the T3SS are regulated as an <i>hrp</i> regulon, activated only when the pathogen encounters the plants, indicating that the pathogen must sense plant signals. For the first time, we identified two signaling compounds, sucrose and malic acid, that are abundantly found in tobacco roots. The <i>hrp</i> operon was induced even in non-host plants, possibly because sucrose and malic acid are common in plants. We also found that <i>R. pseudosolanacearum</i> membrane proteins received sucrose and malic acid independently. As a next step, antagonists of signaling molecules can be screened.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0027324"},"PeriodicalIF":2.7,"publicationDate":"2025-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11925246/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143189405","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}