Heidi Aarø Åmdal

• Filho, Antonio Pedro Ricomini; Khan, Rabia; Åmdal, Heidi Aarø & Petersen, Fernanda Cristina (2019). Conserved Pheromone Production, Response and Degradation by Streptococcus mutans. Frontiers in Microbiology.  ISSN 1664-302X.  10 . doi: 10.3389/fmicb.2019.02140 Full text in Research Archive. Show summary

  Streptococcus mutans, a bacterium with high cariogenic potential, coordinates competence for natural transformation and bacteriocin production via the XIP and CSP pheromones. CSP is effective in inducing bacteriocin responses but not competence in chemically defined media (CDM). This is in contrast to XIP, which is a strong inducer of competence in CDM but can also stimulate bacteriocin genes as a late response. Interconnections between the pathways activated by the two pheromones have been characterized in certain detail in S. mutans UA159, but it is mostly unknown whether such findings are representative for the species. In this study, we used bioassays based on luciferase reporters for the bacteriocin gene cipB and the alternative sigma factor sigX to investigate various S. mutans isolates for production and response to CSP and XIP pheromones in CDM. Similar to S. mutans UA159, endogenous CSP was undetectable in the culture supernatants of all tested strains. During optimization of the bioassay using the cipB reporter, we discovered that the activity of exogenous CSP used as a standard was reduced over time during S. mutans growth. Using a FRET-CSP reporter peptide, we found that S. mutans UA159 was able to degrade CSP, and that such activity was not significantly different in isogenic mutants with deletion of the protease gene htrA or the competence genes sigX, oppD, and comR. CSP cleavage was also detected in all the wild type strains, indicating that this is a conserved feature in S. mutans. For the XIP pheromone, endogenous production was observed in the supernatants of all 34 tested strains at peak concentrations in culture supernatants that varied between 200 and 26000 nM. Transformation in the presence of exogenous XIP was detected in all but one of the isolates. The efficiency of transformation varied, however, among the different strains, and for those with the highest transformation rates, endogenous XIP peak concentrations in the supernatants were above 2000 nM XIP. We conclude that XIP production and inducing effect on transformation, as well as the ability to degrade CSP, are conserved functions among different S. mutans isolates. Understanding the functionality and conservation of pheromone systems in S. mutans may lead to novel strategies to prevent or treat unbalances in oral microbiomes that may favor diseases.

• Junges, Roger; Sturød, Kjersti; Salvadori, Gabriela; Åmdal, Heidi Aarø; Chen, Tsute & Petersen, Fernanda Cristina (2019). Characterization of a Signaling System in Streptococcus mitis That Mediates Interspecies Communication with Streptococcus pneumoniae. Applied and Environmental Microbiology.  ISSN 0099-2240.  85(2) . doi: 10.1128/AEM.02297-18
• Salvadori, Gabriela; Junges, Roger; Åmdal, Heidi Aarø; Chen, T.; Morrison, D.A. & Petersen, Fernanda Cristina (2018). High-resolution profiles of the Streptococcus mitis CSP signaling pathway reveal core and strain-specific regulated genes. BMC Genomics.  ISSN 1471-2164.  19(1) . doi: 10.1186/s12864-018-4802-y Full text in Research Archive.
• Junges, Roger; Khan, Rabia; Tovpeko, Yanina; Åmdal, Heidi Aarø; Petersen, Fernanda Cristina & Morrison, Donald (2017). Markerless genome editing in competent streptococci. Methods in molecular biology.  ISSN 1064-3745.  1537, s 233- 247 . doi: 10.1007/978-1-4939-6685-1_14 Full text in Research Archive.
• Junges, Roger; Salvadori, Gabriela; Shekhar, Sudhanshu; Åmdal, Heidi Aarø; Periselneris, Jimstan; Chen, Tsute; Brown, Jeremy S. & Petersen, Fernanda Cristina (2017). A quorum-sensing system that regulates Streptococcus pneumoniae biofilm formation and surface polysaccharide production. mSphere.  ISSN 2379-5042.  2(5), s 1- 18 . doi: 10.1128/mSphere.00324-17 Full text in Research Archive.
• Khan, Rabia; Junges, Roger; Åmdal, Heidi Aarø; Chen, Tsute; Morrison, Donald A & Petersen, Fernanda Cristina (2017). A positive feedback loop mediated by Sigma X enhances expression of the streptococcal regulator ComR. Scientific Reports.  ISSN 2045-2322.  7(1) . doi: 10.1038/s41598-017-04768-5 Full text in Research Archive.
• Salvadori, Gabriela; Junges, Roger; Khan, Rabia; Åmdal, Heidi Aarø; Morrison, Donald A. & Petersen, Fernanda Cristina (2017). Natural transformation of oral streptococci by use of synthetic pheromones. Methods in molecular biology.  ISSN 1064-3745.  s 219- 232 . doi: 10.1007/978-1-4939-6685-1_13 Full text in Research Archive.
• Khan, Rabia; Rukke, Håkon Valen; Høvik, Hedda; Åmdal, Heidi Aarø; Chen, T.; Morrison, Donald A. & Petersen, Fernanda Cristina (2016). Comprehensive Transcriptome Profiles of Streptococcus mutans UA159 Map Core Streptococcal Competence Genes. mSystems.  ISSN 2379-5077.  1(2) . doi: 10.1128/mSystems.00038-15 Full text in Research Archive. Show summary

  In Streptococcus mutans, an oral colonizer associated with dental caries, development of competence for natural genetic transformation is triggered by either of two types of peptide pheromones, competence-stimulating peptides (CSPs) (18 amino acids [aa]) or SigX-inducing peptides (XIPs) (7 aa). Competence induced by CSP is a late response to the pheromone that requires the response regulator ComE and the XIP-encoding gene comS. XIP binds to ComR to allow expression of the alternative sigma factor SigX and the effector genes it controls. While these regulatory links are established, the precise set of effectors controlled by each regulator is poorly defined. To improve the definition of all three regulons, we used a high-resolution tiling array to map global changes in gene expression in the early and late phases of the CSP response. The early phase of the CSP response was limited to increased gene expression at four loci associated with bacteriocin production and immunity. In the late phase, upregulated regions expanded to a total of 29 loci, including comS and genes required for DNA uptake and recombination. The results indicate that the entire late response to CSP depends on the expression of comS and that the immediate transcriptional response to CSP, mediated by ComE, is restricted to just four bacteriocin-related loci. Comparison of the new data with published transcriptome data permitted the identification of all of the operons in each regulon: 4 for ComE, 2 for ComR, and 21 for SigX. Finally, a core set of 27 panstreptococcal competence genes was identified within the SigX regulon by comparison of transcriptome data from diverse streptococcal species.

• Morrison, D.A.; Khan, Rabia; Junges, Roger; Åmdal, Heidi Aarø & Petersen, Fernanda Cristina (2015). Genome editing by natural genetic transformation in Streptococcus mutans. Journal of Microbiological Methods.  ISSN 0167-7012.  119, s 134- 141 . doi: 10.1016/j.mimet.2015.09.023

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• Junges, Roger; Sturød, Kjersti; Salvadori, Gabriela; Åmdal, Heidi Aarø; Chen, Tsute & Petersen, Fernanda Cristina (2018). Interspecies activation of a virulent pathway by an oral commensal.
• Salvadori, Gabriela; Junges, Roger; Åmdal, Heidi Aarø; Chen, Tsute; Morrison, Donald A & Petersen, Fernanda Cristina (2018). Insights into regulatory pathways of competence development in Streptococcus mitis type strain and SK321.
• Salvadori, Gabriela; Junges, Roger; Åmdal, Heidi Aarø; Chen, Tsute; Morrison, Donald A & Petersen, Fernanda Cristina (2018). Molecular Characterization of Genetic Competence in Streptococcus mitis.
• Junges, Roger; Khan, Rabia; Åmdal, Heidi Aarø; Morrison, Donald A. & Petersen, Fernanda Cristina (2015). A new link between two Streptococcus mutans pheromones.
• Junges, Roger; Khan, Rabia; Åmdal, Heidi Aarø; Morrison, Donald A. & Petersen, Fernanda Cristina (2015). Transcriptome response of Streptoccocus mutans to the sigX-inducing peptide (XIP).
• Junges, Roger; Åmdal, Heidi Aarø; Chen, Tsute & Petersen, Fernanda Cristina (2015). A New Pheromone in Streptococcus mitis Enhances Biofilm Formation.
• Junges, Roger; Åmdal, Heidi Aarø; Chen, Tsute & Petersen, Fernanda Cristina (2015). Characterization of an Rgg/SHP system in Streptococcus mitis that allows communication with Streptococcus pneumoniae.
• Petersen, Fernanda Cristina; Khan, Rabia; Junges, Roger; Åmdal, Heidi Aarø; Chen, Tsute & Morrison, Donald A. (2015). A new link between the Streptococcus mutans XIP and CSP pheromone pathways revealed by directional RNA-sequencing.
• Salvadori, Gabriela; Junges, Roger; Åmdal, Heidi Aarø; Chen, Tsute & Petersen, Fernanda Cristina (2015). Identification of Streptococcus mitis competence pheromone responsive genes by transcriptome analysis.
• Salvadori, Gabriela; Junges, Roger; Åmdal, Heidi Aarø; Chen, Tsute & Petersen, Fernanda Cristina (2015). Transcriptome response of Streptococcus mitis to the competence pheromone.
• Silva, Gabriela Salvadori; Junges, Roger; Åmdal, Heidi Aarø; Chen, Tsute & Petersen, Fernanda Cristina (2015). Streptococcus mitis response to the competence pheromone.
• Silva, Gabriela Salvadori; Junges, Roger; Åmdal, Heidi Aarø; Chen, Tsute & Petersen, Fernanda Cristina (2015). Transcriptome analysis of Streptococcus mitis response to the competence pheromone.

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