Journal of Bacteriology最新文献

{"title":"Robust and highly efficient transformation method for a minimal mycoplasma cell.","authors":"Masaki Mizutani, John I Glass, Takema Fukatsu, Yo Suzuki, Shigeyuki Kakizawa","doi":"10.1128/jb.00415-24","DOIUrl":"10.1128/jb.00415-24","url":null,"abstract":"<p><p>Mycoplasmas have been widely investigated for their pathogenicity, as well as for genomics and synthetic biology. Conventionally, transformation of mycoplasmas was not highly efficient, and due to the low transformation efficiency, large amounts of DNA and recipient cells were required for that purpose. Here, we report a robust and highly efficient transformation method for the minimal cell JCVI-syn3B, which was created through streamlining the genome of <i>Mycoplasma mycoides</i>. When the growth states of JCVI-syn3B were examined in detail by focusing on such factors as pH, color, absorbance, colony forming unit, and transformation efficiency, it was found that the growth phase after the lag phase can be divided into three distinct phases, of which the highest transformation efficiency was observed during the early exponential growth phase. Notably, the transformation efficiency of up to 4.4 × 10^-2 transformants per cell per microgram of plasmid DNA was obtained. A method to obtain several hundred to several thousand transformants with less than 0.2 mL of culture with approximately 1 × 10⁷-10⁸ cells and 10 ng of plasmid DNA was developed. Moreover, a transformation method using a frozen stock of transformation-ready cells was established. These procedures and information could simplify and enhance the transformation process of minimal cells, facilitating advanced genetic engineering and biological research using minimal cells.</p><p><strong>Importance: </strong>Mycoplasmas are parasitic and pathogenic bacteria for many animals. They are also useful bacteria to understand the cellular process of life and for bioengineering because of their simple metabolism, small genomes, and cultivability. Genetic manipulation is crucial for these purposes, but transformation efficiency in mycoplasmas is typically quite low. Here, we report a highly efficient transformation method for the minimal genome mycoplasma JCVI-syn3B. Using this method, transformants can be obtained with only 10 ng of plasmid DNA, which is around one-thousandth of the amount required for traditional mycoplasma transformations. Moreover, a convenient method using frozen stocks of transformation-ready cells was established. These improved methods play a crucial role in further studies using minimal cells.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0041524"},"PeriodicalIF":2.7,"publicationDate":"2025-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11925241/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143189470","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 and DNA methylation play active roles in clinical <i>Burkholderia</i> phase variation.","authors":"Pauline M L Coulon, Marie-Christine Groleau, Abderrahman Hachani, Matthew P Padula, Timothy P Stinear, Eric Déziel","doi":"10.1128/jb.00531-24","DOIUrl":"10.1128/jb.00531-24","url":null,"abstract":"<p><p>Phenotypic diversity in bacteria often results from adaptation to changing environmental conditions, exemplified by variable colony morphotypes. In <i>Burkholderia pseudomallei</i>, discrete genomic alterations and modulation of gene expression facilitate adaptation. Adapted variants of species within the <i>Burkholderia cepacia</i> complex (Bcc) often lose the pC3 virulence megaplasmid, impacting their colony morphology and their production of virulence factors. In this study, we characterize variants arising in <i>Burkholderia ambifaria</i> clinical isolates using proteomics and phenotypic tests and show that some of them have retained the pC3, indicating a distinct phase variation mechanism at play in this Bcc species. Interestingly, variants of <i>B. ambifaria</i> strains CEP0996 (pC3-null) and HSJ1 (pC3-positive) still share similarities in phenotypes controlled by the Cep quorum-sensing (QS) system. We further investigated the role of QS in <i>B. ambifaria</i> HSJ1 phase variation and confirmed that the Cep QS system is important for the emergence of variants. Given that DNA methylation is a key epigenetic factor regulating virulence factors in <i>Burkholderia cenocepacia</i>, we hypothesized that adenosine DNA methylation also governs phase variation in <i>B. ambifaria</i> HSJ1. By deleting the genes encoding putative adenosine DNA methyltransferases, we discovered that an orphan type II DNA methyltransferase inhibits the emergence of phase variants. This study is the first to demonstrate that quorum sensing and adenosine DNA methylation are two antagonistic systems independently controlling phase variation in <i>B. ambifaria</i>.IMPORTANCESome <i>Burkholderia</i> species are pathogenic to plants, animals, or humans. In immunocompromised individuals, and people suffering from cystic fibrosis, infection from the <i>Burkholderia cepacia</i> complex (Bcc) can lead to \"<i>cepacia</i> syndrome.\" In northern Australia and southeast Asia, melioidosis caused by <i>Burkholderia pseudomallei</i> is prevalent among native population, particularly among people with diabetes, chronic lung or kidney disease or alcoholism. <i>Burkholderia</i>'s phenotypic plasticity, including colony morphotype variation (CMV), enables rapid adaptation to diverse environments, enhancing its survival and pathogenicity. This study reveals phase variation as a new CMV mechanism within the Bcc group and is the first to report that quorum sensing and DNA methylation are involved in phase variation. Understanding the underlying mechanisms of CMV could lead to the development of targeted therapies against these highly antibiotic-tolerant bacteria.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0053124"},"PeriodicalIF":2.7,"publicationDate":"2025-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11925244/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143414283","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":"Germination of <i>Bacillus</i> spores by LiCl.","authors":"James Wicander, John Gorsuch, Longjiao Chen, Rebecca Caldbeck, George Korza, Stanley Brul, Graham Christie, Peter Setlow","doi":"10.1128/jb.00510-24","DOIUrl":"10.1128/jb.00510-24","url":null,"abstract":"<p><p>Spores of <i>Bacillus subtilis</i> have been found to germinate when incubated with LiCl, but not with other monovalent or divalent metal cations. <i>Bacillus megaterium</i> spores also germinated with LiCl, but <i>B. cereus</i> spores did not. In <i>B. subtilis</i>, the LiCl germination was via the activation of spores' GerA germinant receptor (GR), and in <i>B. megaterium,</i> it was the GerU GR. Notably, LiCl germination was much slower than normal physiological germinant triggered GR germination. In <i>B. subtilis</i> spores, rates of LiCl germination were increased in spores with a more fluid IM and decreased in spores with a less fluid IM. Analyses of the GerA germinant binding site suggested that Li⁺ could bind in a specific site in the <i>B. subtilis</i> GerAB subunit where normally a Na⁺ likely binds. Importantly, NaCl strongly inhibited LiCl germination of <i>B. subtilis</i> spores, much more so than the larger cation in KCl, although neither salt inhibited L-alanine germination via the GerA GR. These findings increase the understanding of features of mechanisms of germination of <i>Bacillus</i> spores.IMPORTANCEThe ability of some bacteria to form spores upon nutrient starvation confers properties of metabolic dormancy and enhanced resistance to environmental stressors that would otherwise kill vegetative cells. Since spore-forming bacteria include several notable pathogens and economically significant spoilage organisms, insight into how spores are stimulated to germinate and form new vegetative cells is important. Here, we reveal that relatively high concentrations of the inorganic salt lithium chloride trigger the germination of <i>Bacillus subtilis</i> and <i>Bacillus megaterium</i> spores by stimulating one of the spores of each species cohort of nutrient germinant receptors. This is significant since novel germinants and increased knowledge of the germination process should provide opportunities for improved control of spores in healthcare, food, and environmental sectors.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0051024"},"PeriodicalIF":2.7,"publicationDate":"2025-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11925240/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143515502","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":"Broken beyond repair: TA system ParE toxins mediate effective gyrase inhibition without driving resistance.","authors":"Chih-Han Tu, Shengfeng Ruan, Michelle Holt, Christina R Bourne","doi":"10.1128/jb.00416-24","DOIUrl":"10.1128/jb.00416-24","url":null,"abstract":"<p><p>DNA gyrase is an essential bacterial-specific type IIA topoisomerase that corrects DNA overwinding during transcription and replication. Compounds capable of stabilizing gyrase-mediated double-strand DNA breaks are valuable antibacterials; however, these can trigger error-prone repair, potentially inducing DNA mutations leading to antimicrobial resistance. ParE toxin proteins, which belong to a family of type II toxin-antitoxin systems, inhibit DNA gyrase and promote the persistence of double-strand DNA breaks. However, it is unclear if the ParE-induced gyrase inhibition is equivalent for all ParE family members, or if any mutations arise and can accumulate to cause antibiotic resistance. Selected chromosomal ParE toxins were examined for toxicity to their native bacterial hosts, and the frequency of mutations and impact on susceptibility to selected antibiotics were assessed. Our results show that ParE toxins from <i>Burkholderia cenocepacia</i>, <i>Mycobacterium tuberculosis</i>, <i>Pseudomonas aeruginosa</i>, and <i>Vibrio cholerae</i> exert potent toxicities toward the native cells, whereas one tested ParE toxin from <i>P. aeruginosa</i> was not toxic. The contribution to toxicity of the ParE toxin C-terminal amino acid sequences was examined using two lab-generated chimeric ParE toxins; our results demonstrate that this region did not impact the toxicity level. Our study finds that the relative potency of individual ParE toxins correlates with increases in mutation frequency. While some ParE toxins induced limited collateral sensitivity to selected antibiotics, no increases in MIC values were found. Overall, this study demonstrates the relative toxicity of different ParE toxins. Importantly, the toxicity appears to result in loss of viability before productive resistance-inducing mutations can accumulate.</p><p><strong>Importance: </strong>Toxin-antitoxin (TA) systems can halt growth or kill cells when the toxin protein engages with the host cell target. In the ParDE TA system, the toxin ParE inhibits DNA gyrase, resulting in loss of viability that phenocopies fluoroquinolone antibiotics. Our study demonstrates that ParE toxins increase the frequency of mutations, presumably by a mechanism similar to fluoroquinolone antibiotics. These increases scale to the resulting toxicity, and importantly, these mutations do not accumulate into productive antibacterial resistance. This suggests that ParE toxins are not intrinsic drivers of resistance and, if the molecular mechanism can be harnessed, could generate a new class of gyrase inhibitors.</p>","PeriodicalId":15107,"journal":{"name":"Journal of Bacteriology","volume":" ","pages":"e0041624"},"PeriodicalIF":2.7,"publicationDate":"2025-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11925232/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143542072","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":"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":"<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":"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":"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}