RNA-mediated gene regulation in Neisseria meningitidis and other nasopharyngeal pathogens
Author: Eichner, Hannes
Date: 2021-06-04
Location: BioClinicum, Room J3:12 Nanna Svartz, Solnavägen 30, Nya Karolinska Sjukhuset, Solna
Time: 09.00
Department: Inst för mikrobiologi, tumör- och cellbiologi / Dept of Microbiology, Tumor and Cell Biology
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Thesis (5.489Mb)
Abstract
Neisseria meningitidis is a transient commensal bacterium of the upper respiratory tract and spreads through respiratory secretions produced by the carrier. While mostly harmless, the bacterium can cause invasive meningococcal disease by entering the circulatory system, leading to septicaemia and/or meningitis. It is widely theorised that the disease is the result of accidental dysfunctional gene regulation based on its genome plasticity. High mutation rates, genome re-arrangement and horizontal gene transfer may lead to a phenotype that is more immune evasive, more invasive, or better adapted to survive in the nasopharynx for an extended amount of time. Differential gene regulation is suggested to play a role in the ability of N. meningitidis to cause disease. This thesis presents several aspects of RNA-mediated gene regulation in N. meningitidis as an energy efficient mode of gene expression control. It is further demonstrated that Streptococcus pneumoniae and Haemophilus influenzae have developed a similar strategy to evade the immune system by sensing temperature.
The temperature in the nasopharynx is slightly cooler than body temperature, which leads to adaption of colonising bacteria. Inflammation through immune responses can lead to higher temperature in that niche, serving as a warning signal for bacteria. Studies in this thesis unveiled, that S. pneumoniae and H. influenzae control production of their immune evasive polysaccharide capsule und factor H binding proteins by RNA thermosensors. Identifying the same ability in clinical isolates of S. pneumoniae suggests that the mode of temperature-based gene regulation is of advantage for nasopharyngeal bacteria and dysregulation may lead to invasive disease. In N. meningitidis, analysis of disease and carrier isolates uncovered a tandem repeat configuration in the RNA thermosensor that regulates its polysaccharide capsule production. Specific tandem repeat configurations induced higher capsulated phenotypes which were more associated with isolates that cause invasive disease.
Other work in this thesis explored the ability of N meningitidis to scavenge nutrients in the nasopharynx. Two thiamine pyrophosphate dependent riboswitches were identified and linked to nutrient acquisition from dead bacteria. Salvaging thiamine from the environment and turning off de novo biosynthesis via the riboswitch can conserve energy and may facilitate colonisation. Furthermore, a novel cis-encoded RNA element has been identified to contain the Correia Repeat Enclosed Element (CREE), a repetitive sequence of the Neisseria genus genome. The work demonstrates that a CREE can be transcribed as the regulatory RNA Crrp. It interacts with other CREEs located on 5′-untranslated regions of mRNAs involved in type IV pilus biosynthesis, therefore influencing the natural competence and cell adhesion ability of N. meningitidis. In summary, this thesis demonstrates similarities in immune evasion control of nasopharyngeal pathogens and expands the knowledge about regulation of gene expression in N. meningitidis.
The temperature in the nasopharynx is slightly cooler than body temperature, which leads to adaption of colonising bacteria. Inflammation through immune responses can lead to higher temperature in that niche, serving as a warning signal for bacteria. Studies in this thesis unveiled, that S. pneumoniae and H. influenzae control production of their immune evasive polysaccharide capsule und factor H binding proteins by RNA thermosensors. Identifying the same ability in clinical isolates of S. pneumoniae suggests that the mode of temperature-based gene regulation is of advantage for nasopharyngeal bacteria and dysregulation may lead to invasive disease. In N. meningitidis, analysis of disease and carrier isolates uncovered a tandem repeat configuration in the RNA thermosensor that regulates its polysaccharide capsule production. Specific tandem repeat configurations induced higher capsulated phenotypes which were more associated with isolates that cause invasive disease.
Other work in this thesis explored the ability of N meningitidis to scavenge nutrients in the nasopharynx. Two thiamine pyrophosphate dependent riboswitches were identified and linked to nutrient acquisition from dead bacteria. Salvaging thiamine from the environment and turning off de novo biosynthesis via the riboswitch can conserve energy and may facilitate colonisation. Furthermore, a novel cis-encoded RNA element has been identified to contain the Correia Repeat Enclosed Element (CREE), a repetitive sequence of the Neisseria genus genome. The work demonstrates that a CREE can be transcribed as the regulatory RNA Crrp. It interacts with other CREEs located on 5′-untranslated regions of mRNAs involved in type IV pilus biosynthesis, therefore influencing the natural competence and cell adhesion ability of N. meningitidis. In summary, this thesis demonstrates similarities in immune evasion control of nasopharyngeal pathogens and expands the knowledge about regulation of gene expression in N. meningitidis.
List of papers:
I. Hannes Eichner, Jens Karlsson, Laura Spelmink, Anuj Pathak, Lok-To Sham, Birgitta Henriques-Normark*, Edmund Loh*. RNA thermosensors facilitate Streptococcus pneumoniae and Haemophilus influenzae immune evasion. PLoS Pathogens. 2021, 17(4), e1009513. *Joint last authors.
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II. Jens Karlsson, Hannes Eichner, Cecilia Andersson, Susanne Jacobsson, Edmund Loh. Novel hypercapsulation RNA thermosensor variants in Neisseria meningitidis and their association with invasive meningococcal disease: a genetic and phenotypic investigation and molecular epidemiological study. Lancet Microbe. 2020; 1: e319–27.
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III. Francesco Righetti, Solange Lise Materne, John Boss, Hannes Eichner, Emmanuelle Charpentier, Edmund Loh. Characterization of a transcriptional TPP riboswitch in the human pathogen Neisseria meningitidis. RNA Biology. 2020, Vol. 17, No. 5, 718-730.
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IV. Christian Spoerry#, Hannes Eichner#, Francesco Righetti#, Jens Karlsson, John Boss, Edmund Loh. A novel non-coding RNA containing a Correia Repeat Enclosed Element influences piliation in Neisseria meningitidis. #Joint first authors. [Manuscript]
I. Hannes Eichner, Jens Karlsson, Laura Spelmink, Anuj Pathak, Lok-To Sham, Birgitta Henriques-Normark*, Edmund Loh*. RNA thermosensors facilitate Streptococcus pneumoniae and Haemophilus influenzae immune evasion. PLoS Pathogens. 2021, 17(4), e1009513. *Joint last authors.
Fulltext (DOI)
Pubmed
View record in Web of Science®
II. Jens Karlsson, Hannes Eichner, Cecilia Andersson, Susanne Jacobsson, Edmund Loh. Novel hypercapsulation RNA thermosensor variants in Neisseria meningitidis and their association with invasive meningococcal disease: a genetic and phenotypic investigation and molecular epidemiological study. Lancet Microbe. 2020; 1: e319–27.
Fulltext (DOI)
View record in Web of Science®
III. Francesco Righetti, Solange Lise Materne, John Boss, Hannes Eichner, Emmanuelle Charpentier, Edmund Loh. Characterization of a transcriptional TPP riboswitch in the human pathogen Neisseria meningitidis. RNA Biology. 2020, Vol. 17, No. 5, 718-730.
Fulltext (DOI)
Pubmed
View record in Web of Science®
IV. Christian Spoerry#, Hannes Eichner#, Francesco Righetti#, Jens Karlsson, John Boss, Edmund Loh. A novel non-coding RNA containing a Correia Repeat Enclosed Element influences piliation in Neisseria meningitidis. #Joint first authors. [Manuscript]
Supervisor: Loh, Edmund
Co-supervisor: Henriques-Normark, Birgitta; Normark, Staffan
Issue date: 2021-05-07
Rights:
Publication year: 2021
ISBN: 978-91-8016-169-5
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