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Basta DW, Campbell IW, Sullivan EJ, Hotinger JA, Hullahalli K, Waldor MK. Inducible transposon mutagenesis for genome-scale forward genetics. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.05.21.595064. [PMID: 38826325 PMCID: PMC11142078 DOI: 10.1101/2024.05.21.595064] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2024]
Abstract
Transposon insertion sequencing (Tn-seq) is a powerful method for genome-scale functional genetics in bacteria. However, its effectiveness is often limited by a lack of mutant diversity, caused by either inefficient transposon delivery or stochastic loss of mutants due to population bottlenecks. Here, we introduce "InducTn-seq", which leverages inducible mutagenesis for temporal control of transposition. InducTn-seq generates millions of transposon mutants from a single colony, enabling the sensitive detection of subtle fitness defects and transforming binary classifications of gene essentiality into a quantitative fitness measurement across both essential and non-essential genes. Using a mouse model of infectious colitis, we show that InducTn-seq bypasses a highly restrictive host bottleneck to generate a diverse transposon mutant population from the few cells that initiate infection, revealing the role of oxygen-related metabolic plasticity in pathogenesis. Overall, InducTn-seq overcomes the limitations of traditional Tn-seq, unlocking new possibilities for genome-scale forward genetic screens in bacteria.
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Affiliation(s)
- David W. Basta
- Department of Pathology, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, USA
| | - Ian W. Campbell
- Division of Infectious Diseases, Brigham and Women’s Hospital, Boston, MA, USA
- Department of Microbiology, Harvard Medical School, Boston, MA, USA
| | - Emily J. Sullivan
- Division of Infectious Diseases, Brigham and Women’s Hospital, Boston, MA, USA
- Department of Microbiology, Harvard Medical School, Boston, MA, USA
| | - Julia A Hotinger
- Division of Infectious Diseases, Brigham and Women’s Hospital, Boston, MA, USA
- Department of Microbiology, Harvard Medical School, Boston, MA, USA
| | - Karthik Hullahalli
- Division of Infectious Diseases, Brigham and Women’s Hospital, Boston, MA, USA
- Department of Microbiology, Harvard Medical School, Boston, MA, USA
| | - Matthew K. Waldor
- Division of Infectious Diseases, Brigham and Women’s Hospital, Boston, MA, USA
- Department of Microbiology, Harvard Medical School, Boston, MA, USA
- Howard Hughes Medical Institute, Boston, MA, USA
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Lokken-Toyli KL, Aggarwal SD, Bee GCW, de Steenhuijsen Piters WAA, Wu C, Chen KZM, Loomis C, Bogaert D, Weiser JN. Impaired upper respiratory tract barrier function during postnatal development predisposes to invasive pneumococcal disease. PLoS Pathog 2024; 20:e1012111. [PMID: 38718049 PMCID: PMC11078396 DOI: 10.1371/journal.ppat.1012111] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2023] [Accepted: 03/10/2024] [Indexed: 05/12/2024] Open
Abstract
Infants are highly susceptible to invasive respiratory and gastrointestinal infections. To elucidate the age-dependent mechanism(s) that drive bacterial spread from the mucosa, we developed an infant mouse model using the prevalent pediatric respiratory pathogen, Streptococcus pneumoniae (Spn). Despite similar upper respiratory tract (URT) colonization levels, the survival rate of Spn-infected infant mice was significantly decreased compared to adults and corresponded with Spn dissemination to the bloodstream. An increased rate of pneumococcal bacteremia in early life beyond the newborn period was attributed to increased bacterial translocation across the URT barrier. Bacterial dissemination in infant mice was independent of URT monocyte or neutrophil infiltration, phagocyte-derived ROS or RNS, inflammation mediated by toll-like receptor 2 or interleukin 1 receptor signaling, or the pore-forming toxin pneumolysin. Using molecular barcoding of Spn, we found that only a minority of bacterial clones in the nasopharynx disseminated to the blood in infant mice, indicating the absence of robust URT barrier breakdown. Rather, transcriptional profiling of the URT epithelium revealed a failure of infant mice to upregulate genes involved in the tight junction pathway. Expression of many such genes was also decreased in early life in humans. Infant mice also showed increased URT barrier permeability and delayed mucociliary clearance during the first two weeks of life, which corresponded with tighter attachment of bacteria to the respiratory epithelium. Together, these results demonstrate a window of vulnerability during postnatal development when altered mucosal barrier function facilitates bacterial dissemination.
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Affiliation(s)
- Kristen L. Lokken-Toyli
- Department of Microbiology, New York University School of Medicine, New York, New York, United States of America
| | - Surya D. Aggarwal
- Department of Microbiology, New York University School of Medicine, New York, New York, United States of America
| | - Gavyn Chern Wei Bee
- Department of Microbiology, New York University School of Medicine, New York, New York, United States of America
| | - Wouter A. A. de Steenhuijsen Piters
- Department of Paediatric Immunology and Infectious Diseases, Wilhelmina Children’s Hospital/University Medical Center Utrecht, Utrecht, the Netherlands
- National Institute for Public Health and the Environment, Bilthoven, the Netherlands; Department of Parasitology, Leiden University Medical Center, Leiden, the Netherlands
| | - Cindy Wu
- Department of Microbiology, New York University School of Medicine, New York, New York, United States of America
| | - Kenny Zhi Ming Chen
- Department of Microbiology, New York University School of Medicine, New York, New York, United States of America
| | - Cynthia Loomis
- Department of Pathology, New York University School of Medicine, New York, New York, United States of America
| | - Debby Bogaert
- Department of Paediatric Immunology and Infectious Diseases, Wilhelmina Children’s Hospital/University Medical Center Utrecht, Utrecht, the Netherlands
- Centre for Inflammation Research, Institute for Regeneration and Repair, Queen’s Medical Research Institute, University of Edinburgh, Edinburgh, United Kingdom
| | - Jeffrey N. Weiser
- Department of Microbiology, New York University School of Medicine, New York, New York, United States of America
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McAnulty MJ, Guron GK, Oest AM, Miller AL, Renye JA. The quorum sensing peptide BlpC regulates the transcription of genes outside its associated gene cluster and impacts the growth of Streptococcus thermophilus. Front Microbiol 2024; 14:1304136. [PMID: 38293552 PMCID: PMC10826417 DOI: 10.3389/fmicb.2023.1304136] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2023] [Accepted: 12/08/2023] [Indexed: 02/01/2024] Open
Abstract
Bacteriocin production in Streptococcus thermophilus is regulated by cell density-dependent signaling molecules, including BlpC, which regulates transcription from within the bacteriocin-like peptide (blp) gene cluster. In some strains, such as S. thermophilus ST106, this signaling system does not function properly, and BlpC must be supplied exogenously to induce bacteriocin production. In other strains, such as S. thermophilus B59671, bacteriocin (thermophilin 110 in strain B59671) production occurs naturally. Here, transcriptomic analyses were used to compare global gene expression within ST106 in the presence or absence of synthetic BlpC and within B59671 to determine if BlpC regulates the expression of genes outside the blp cluster. Real-time semi-quantitative PCR was used to find genes differentially expressed in the absence of chromosomal blpC in the B59671 background. Growth curve experiments and bacteriocin activity assays were performed with knockout mutants and BlpC supplementation to identify effects on growth and bacteriocin production. In addition to the genes involved in bacteriocin production, BlpC affected the expression of several transcription regulators outside the blp gene cluster, including a putative YtrA-subfamily transcriptional repressor. In strain B59671, BlpC not only regulated the expression of thermophilin 110 but also suppressed the production of another bacteriocin, thermophilin 13, and induced the same YtrA-subfamily transcriptional repressor identified in ST106. Additionally, it was shown that the broad-spectrum antimicrobial activity associated with strain B59671 was due to the production of thermophilin 110, while thermophilin 13 appears to be a redundant system for suppressing intraspecies growth. BlpC production or induction negatively affected the growth of strains B59671 and ST106, revealing selective pressure to not produce bacteriocins that may explain bacteriocin production phenotype differences between S. thermophilus strains. This study identifies additional genes regulated by BlpC and assists in defining conditions to optimize the production of bacteriocins for applications in agriculture or human and animal health.
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Affiliation(s)
- Michael J. McAnulty
- Dairy and Functional Foods Research Unit, Eastern Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, Wyndmoor, PA, United States
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Bisaro F, Shuman HA, Feldman MF, Gebhardt MJ, Pukatzki S. Acinetobacter baumannii ATCC 17978 encodes a microcin system with antimicrobial properties for contact-independent competition. MICROBIOLOGY (READING, ENGLAND) 2023; 169:001346. [PMID: 37289493 PMCID: PMC10333792 DOI: 10.1099/mic.0.001346] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2023] [Accepted: 05/25/2023] [Indexed: 06/09/2023]
Abstract
Acinetobacter baumannii is a multidrug-resistant opportunistic pathogen that persists in the hospital environment and causes various clinical infections, primarily affecting immunocompromised patients. A. baumannii has evolved a wide range of mechanisms to compete with neighbouring bacteria. One such competition strategy depends on small secreted peptides called microcins, which exert antimicrobial effects in a contact-independent manner. Here, we report that A. baumannii ATCC 17978 (AB17978) encodes the class II microcin 17 978 (Mcc17978) with antimicrobial activity against closely related Acinetobacter, and surprisingly, also Escherichia coli strains. We identified the genetic locus encoding the Mcc17978 system in AB17978. Using classical bacterial genetic approaches, we determined that the molecular receptor of Mcc17978 in E. coli is the iron-catecholate transporter Fiu, and in Acinetobacter is Fiu's homolog, PiuA. In bacteria, the Ferric uptake regulator (Fur) positively regulates siderophore systems and microcin systems under iron-deprived environments. We found that the Mcc17978 system is upregulated under low-iron conditions commonly found in the host environment and identified a putative Fur binding site upstream of the mcc17978 gene. When we tested the antimicrobial activity of Mcc17978 under different levels of iron availability, we observed that low iron levels not only triggered transcriptional induction of the microcin, but also led to enhanced microcin activity. Taken together, our findings suggest that A. baumannii may utilize microcins to compete with other microbes for resources during infection.
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Affiliation(s)
- Fabiana Bisaro
- Department of Biology, The City College, City University of New York, New York, NY 10031, USA
- Department of Molecular Microbiology, Washington University School of Medicine in St. Louis, St. Louis MO 63110, USA
| | - Howard A. Shuman
- Department of Microbiology, The University of Chicago, Chicago, IL 60637, USA
- Present address: P.O. Box 1088, Sheffield, MA 01257, USA
| | - Mario F. Feldman
- Department of Molecular Microbiology, Washington University School of Medicine in St. Louis, St. Louis MO 63110, USA
| | - Michael J. Gebhardt
- Department of Microbiology and Immunology, University of Iowa, Iowa City, Iowa 52242, USA
| | - Stefan Pukatzki
- Department of Biology, The City College, City University of New York, New York, NY 10031, USA
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A selfish bacteriocin dictates pneumococcal domination. Cell Host Microbe 2023; 31:7-8. [PMID: 36634623 DOI: 10.1016/j.chom.2022.12.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Efficient colonization of new hosts is critical for survival of Streptococcus pneumoniae. In this issue of Cell Host & Microbe, Aggarwal et al. investigate the population dynamics of this process, demonstrating how a quorum-sensing bacteriocin locus promotes survival of individual clonal lineages, providing a population bottleneck and restricting genetic diversity.
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