Fernanda Cristina Petersen

• Ercoli, Jimstan; Ercoli, Giuseppe; Pollard, Tracey; Chimalapati, Suneeta; Camberlein, Emilie; Szylar, Gabriella; Hyams, Catherine; Tomlinson, Gillian; Petersen, Fernanda Cristina; Andres Floto, R; Noursadeghi, Mahdad & Browna, Jeremy S (2019). Relative contributions of extracellular and internalized bacteria to early macrophage proinflammatory responses to streptococcus pneumoniae. mBio.  ISSN 2161-2129.  10(5) . doi: 10.1128/mBio.02144-19
• 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.

• Geissler, Sebastian; Gomez-Florit, Manuel; Wiedmer, David; Barrantes Bautista, Alejandro; Petersen, Fernanda Cristina & Tiainen, Hanna (2019). In vitro performance of bioinspired phenolic nanocoatings for endosseous implant applications. ACS Biomaterials Science and Engineering.  ISSN 2373-9878.  5(7), s 3340- 3351 . doi: 10.1021/acsbiomaterials.9b00566 Full text in Research Archive.
• Junges, Roger; Maienschein-Cline, Mark; Morrison, Donald A. & Petersen, Fernanda Cristina (2019). Complete Genome Sequence of Streptococcus pneumoniae Serotype 19F Strain EF3030. Microbiology Resource Announcements (MRA).  ISSN 2169-8287.  8(19), s 1- 3 . doi: 10.1128/MRA.00198-19
• Junges, Roger; Salvadori, Gabriela; Chen, Tsute; Morrison, Donald A. & Petersen, Fernanda Cristina (2019). Hidden Gems in the Transcriptome Maps of Competent Streptococci. Frontiers in Molecular Biosciences.  ISSN 2296-889X.  5, s 1- 7 . doi: 10.3389/fmolb.2018.00116 Full text in Research Archive.
• 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
• Khan, Rabia; Petersen, Fernanda Cristina & Shekhar, Sudhanshu (2019). Commensal bacteria: An emerging player in defense against respiratory pathogens. Frontiers in Immunology.  ISSN 1664-3224.  10:1203(MAY), s 1- 9 . doi: 10.3389/fimmu.2019.01203 Full text in Research Archive.
• Salvadori, Gabriela; Junges, Roger; Morrison, Donald A. & Petersen, Fernanda Cristina (2019). Competence in Streptococcus pneumoniae and Close Commensal Relatives: Mechanisms and Implications. Frontiers in Cellular and Infection Microbiology.  ISSN 2235-2988.  9:94, s 1- 8 . doi: 10.3389/fcimb.2019.00094 Full text in Research Archive.
• Shekhar, Sudhanshu; Khan, Rabia; Khan, Ata Ul Razzaq & Petersen, Fernanda Cristina (2019). Mouse IgG2a Antibodies Specific for the Commensal Streptococcus mitis Show Stronger Cross-Reactivity with Streptococcus pneumoniae than IgG1 Antibodies. Journal of Immunology Research.  ISSN 2314-8861.  2019 . doi: 10.1155/2019/7906724 Full text in Research Archive.
• Shekhar, Sudhanshu; Khan, Rabia; Schenck, Karl & Petersen, Fernanda Cristina (2019). Intranasal Immunization with the Commensal Streptococcus mitis Confers Protective Immunity against Pneumococcal Lung Infection. Applied and Environmental Microbiology.  ISSN 0099-2240.  85(6) . doi: 10.1128/AEM.02235-18
• Sturød, Kjersti; Dhariwal, Achal; Dahle, Ulf R; Vestrheim, Didrik Frimann & Petersen, Fernanda Cristina (2019). Impact of narrow-spectrum penicillin V on the oral and faecal resistome in a young child treated for otitis media. Journal of Global Antimicrobial Resistance.  ISSN 2213-7165.  20, s 290- 297 . doi: https://doi.org/10.1016/j.jgar.2019.08.004 Full text in Research Archive.
• Lauren A., Cowley; Petersen, Fernanda Cristina; Junges, Roger; Jimenez, M; Morrison, Donald A. & Hanage, WP (2018). Evolution via recombination: Cell-to-cell contact facilitates larger recombination events in Streptococcus pneumoniae. PLoS Genetics.  ISSN 1553-7390.  14(6) . doi: 10.1371/journal.pgen.1007410 Full text in Research Archive.
• Reglinski, Mark; Ercoli, Giuseppe; Plumptre, Charlie; Kay, Emily; Petersen, Fernanda Cristina; Paton, James C; Wren, Brendan W. & Brown, Jeremy (2018). A recombinant conjugated pneumococcal vaccine that protects against murine infections with a similar efficacy to Prevnar-13. npj Vaccines.  ISSN 2059-0105.  3, s 1- 11 . doi: 10.1038/s41541-018-0090-4 Full text in Research Archive.
• 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.
• Shekhar, Sudhanshu; Khan, Rabia; Ferreira, Daniela M.; Mitsi, Elena; German, Esther; Rørvik, Gro Herredsvela; Berild, Dag; Schenck, Karl; Kwon, Keehwan & Petersen, Fernanda Cristina (2018). Antibodies reactive to commensal Streptococcus mitis show cross-reactivity with virulent Streptococcus pneumoniae serotypes. Frontiers in Immunology.  ISSN 1664-3224.  9:747, s 1- 10 . doi: 10.3389/fimmu.2018.00747 Full text in Research Archive. Show summary

  Current vaccines against Streptococcus pneumoniae, a bacterial species that afflicts people by causing a wide spectrum of diseases, do not protect against all pneumococcal serotypes. Thus, alternative vaccines to fight pneumococcal infections that target common proteins are under investigation. One promising strategy is to take advantage of immune cross-reactivity between commensal and pathogenic microbes for cross-protection. In this study, we examined the antibody-mediated cross-reactivity between S. pneumoniae and Streptococcus mitis, a commensal species closely related to S. pneumoniae. Western blot analysis showed that rabbit antisera raised against S. mitis reacted with multiple proteins of virulent S. pneumoniae strains (6B, TIGR4, and D39). Rabbit anti-S. pneumoniae IgG antibodies also showed binding to S. mitis antigens. Incubation of rabbit antisera raised against S. mitis with heterologous or homologous bacterial lysates resulted in marked inhibition of the developments of bands in the Western blots. Furthermore, plasma IgG antibodies from adult human volunteers intranasally inoculated with S. pneumoniae 6B revealed enhanced S. mitis-specific IgG titers compared with the pre-inoculation samples. Using an on-chip protein microarray representing a number of selected membrane and extracellular S. pneumoniae proteins, we identified choline-binding protein D (CbpD), cell division protein (FtsH), and manganese ABC transporter or manganese-binding adhesion lipoprotein (PsaA) as common targets of the rabbit IgG antibodies raised against S. mitis or S. pneumoniae. Cumulatively, these findings provide evidence on the antibody-mediated cross-reactivity of proteins from S. mitis and S. pneumoniae, which may have implications for development of effective and wide-range pneumococcal vaccines.

• Shekhar, Sudhanshu; Schenck, Karl & Petersen, Fernanda Cristina (2018). Exploring Host–Commensal Interactions in the Respiratory Tract. Frontiers in Immunology.  ISSN 1664-3224.  8, s 1- 7 . doi: 10.3389/fimmu.2017.01971 Full text in Research Archive. Show summary

  Commensal microbes are currently in the limelight in biomedical research because they play an important role in health and disease. Humans harbor an enormous diversity of commensals in various parts of the body, including the gastrointestinal and respiratory tracts. Advancement in metagenomic and other omic approaches, and development of suitable animal models have provided an unprecedented appreciation into the diversity of commensals, and the intricacies of their intimate communication with the host immune system. Most studies have focused on the host–commensal interaction in the gut, while less is known on this relationship in other sites of the body, such as the respiratory tract. In this article, we review emerging data from human and animal studies on the host responses to respiratory commensals, immune cross-reactivity between commensals and pathogens, and use of commensals as a vaccine delivery system. A better understanding of the delicate interplay between commensals and host may aid in efforts to develop effective vaccines and therapeutics.

• Sturød, Kjersti; Salvadori, Gabriela; Junges, Roger & Petersen, Fernanda Cristina (2018). Antibiotics alter the window of competence for natural transformation in streptococci. Molecular Oral Microbiology.  ISSN 2041-1006.  33(5), s 378- 387 . doi: 10.1111/omi.12240
• Wiedmer, David; Cui, Chen; Weber, Florian; Petersen, Fernanda Cristina & Tiainen, Hanna (2018). Antibacterial Surface Coating for Bone Scaffolds Based on the Dark Catalytic Effect of Titanium Dioxide. ACS Applied Materials & Interfaces.  ISSN 1944-8244.  10(42), s 35784- 35793 . doi: 10.1021/acsami.8b12623 Full text in Research Archive.
• Engen, Stian André; Schreurs, Olaf Joseph Franciscus; Petersen, Fernanda Cristina; Blix, Inger Johanne S.; Bækkevold, Espen Sønderaal & Schenck, Karl (2017). The Regulatory Role of the Oral Commensal Streptococcus mitis on Human Monocytes. Scandinavian Journal of Immunology.  ISSN 0300-9475.  87(2), s 80- 87 . doi: 10.1111/sji.12636
• 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.
• Rukke, Håkon Valen; Scheie, Anne Aamdal & Petersen, Fernanda Cristina (2017). Oral mikroflora - et reservoar av antibiotikaresistensgener. Aktuell Nordisk odontologi.  ISSN 1902-3545.  s 43- 59 . doi: 10.18261 Show summary

  Et av de store fremskrittene innen medisinen i det forrige århundre var oppdagelsen av antibiotika. Kort tid etter introduksjonen av ulike antibiotika oppdaget man at bakteriene kunne bli resistente. Resistens mot antibiotika er en global trussel og utfordring. Bare innen Den europeiske union, Island og Norge var det estimert at infeksjoner med antibiotikaresistente bakterier kostet 25.000 mennesker livet i 2007. Bakterier kan bli resistente enten ved spontane mutasjoner eller ved opptak av DNA fra miljøet, en prosess kjent som horisontal genoverføring. Gener som gir opphav til resistens, finnes i miljøet rundt oss og i den humane normalflora, inkludert den orale mikrobiota. Normalfloraen utgjør et reservoar av resistensgener, som kan overføres til mer patogene bakterier. Bruk av antibiotika selekterer for resistente bakterier og kan stimulere til horisontal genoverføring. Økningen av resistente bakterier krever en bevisst holdning til forskrivelse og bruk av antibiotika. Bruk bør forbeholdes og være basert på evidensbasert kunnskap, der det er til nytte for pasienten.

• 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.

View all works in Cristin

• Bergersen, Linda Hildegard; Bjorvand Bjørkøy, Aasta Marie; Fei Fang, Evandro; Gjelsvik, Olav; Hystad Hove, Lene; Liaaen Jensen, Janicke; Markussen, Simen; Melberg, Hans Olav; Loge Nilsen, Hilde; Petersen, Fernanda Cristina; Pettersen, Tove & Storm-Mathisen, Jon (2020). Vi må kunne tenke nytt om alderdom.
• Petersen, Fernanda Cristina (2020). Metagenomic approaches for analysis of AMR in microbiomes.
• Petersen, Fernanda Cristina (2020). Towards epi-omic approaches in the study of microbiomes.
• Rajar, Polona & Petersen, Fernanda Cristina (2020). Born in the twilight of antibiotics: Implications of antibiotic use to the preterm infant respiratory microbiome and resistome development.
• Baker, Jonathon & Petersen, Fernanda Cristina (2019). Exploiting the oral microbiome to prevent tooth decay: has evolution already provided the best tools?.
• Baker, Jonathon & Petersen, Fernanda Cristina (2019). Klebsiella and Providencia emerge as lone survivors following long-term starvation of oral microbiota. Show summary

  Abstract: It is well-understood that many bacteria have evolved to survive catastrophic events using a variety of mechanisms, which include expression of stress-response genes, quiescence, necrotrophy, and metabolic advantages obtained through mutation. However, the dynamics of individuals leveraging these abilities to gain a competitive advantage in an ecologically complex setting remain unstudied. In this study, we observed the saliva microbiome throughout the ecological perturbation of long-term starvation, allowing only the species best equipped to access and use the limited resources to survive. During the first several days, the community underwent a death phase that resulted in a ∼50–100-fold reduction in the number of viable cells. Interestingly, after this death phase, only three species, Klebsiella pneumoniae, Klebsiella oxytoca, and Providencia alcalifaciens, all members of the family Enterobacteriaceae, appeared to be transcriptionally active and recoverable. Klebsiella are significant human pathogens, frequently resistant to multiple antibiotics, and recently, ectopic colonization of the gut by oral Klebsiella was documented to induce dysbiosis and inflammation. MetaOmics analyses provided several leads for further investigation regarding the ecological success of the Enterobacteriaceae. The isolates accumulated single nucleotide polymorphisms in known growth advantage in stationary phase alleles and produced natural products closely resembling antimicrobial cyclic depsipeptides. The results presented in this study suggest that pathogenic Enterobacteriaceae persist much longer than their more benign neighbors in the salivary microbiome when faced with starvation. This is particularly significant, given that hospital surfaces contaminated with oral fluids, especially sinks and drains, are well-established sources of outbreaks of drug-resistant Enterobacteriaceae.

• Barbara, E Costa-Oliveira & Petersen, Fernanda Cristina (2019). New insights on Intracellular polysaccharides in Streptococcus mutans. Show summary

  Abstract: The cariogenic biofilm is formed under a dynamic condition of exposing to high carbohydrate concentration (abundance), followed by long periods of nutrients lack (starvation). Under abundance, S. mutans is able to produce acids and also convert the excess of carbohydrates into Intracellular polysaccharides (IPS), a glycogen-like molecule formed by repeated glucose units. Despite unclear, it is believed that IPS could play an important role on energy storage, once S. mutans enzymes can break IPS and generate free glucose for metabolization when extracellular carbohydrate sources deplete. Thus, IPS would contribute on bacterial survival, enhancing bacterial persistence. Additionally, IPS degradation during starvation would be important for keeping acid production, increasing tooth demineralization even when no carbohydrate is available, an important issue that needs more attention. According to RNAseq data, genes responsible to regulate IPS synthesis and degradation are encoded in glg operon and includes glgA (synthase), glgB (branching enzyme), glgC&D (ADP-Glc pyrophosphorylase), and glgP/phsG (phosphorylase). Recent studies have demonstrated that glg operon expression increased under glucose-limiting conditions and downgraded its transcription by the presence of sucrose (Zeng and Burne, 2015). On the other hand, when IPS production was assessed, higher amounts of IPS were formed when cariogenic biofilms were exposed to sucrose (Costa Oliveira et al., 2017). These findings highlight that the mechanisms regulating IPS gene expression and its impact on IPS synthesis and degradation are not well understood. Moreover, the higher amounts of IPS formed in the presence of sucrose and why sucrose was source for increased IPS formation need further investigation. We believe that dissecting the molecular basis for the alterations in these metabolic properties and virulence-related traits (e.g. carbohydrate metabolism, persistence, acid tolerance) will lead to a better understanding of pathogenesis by S. mutans. Also, evaluate IPS metabolism in the presence of sucrose (gene regulation, enzymatic activities, and effects on virulence) would help us to find out if the cariogenicity of sucrose would go beyond extracellular polysaccharide synthesis and acid production.

• Campos Vieira, Juliana & Petersen, Fernanda Cristina (2019). Cariogenicity of lactose in a Streptococcus mutans biofilm exposed to sucrose. Show summary

  Abstract: Breastfeeding is recognized for several benefits in health, physical, and mental development of infants (Victora et al., 2016). Despite of breastfeeding benefits, dental caries has been pointed out as the only negative result for infants' health (Tham et al., 2015; Victora et al., 2016). Although breastfeeding has been associated to dental caries, this relationship is not well understood, mainly because that the incidence of dental caries usually occurs with prolonged breastfeeding. Additionally, it occurs especially in children with nocturnal breastfeeding habit (Victora et al., 2016; Peres et al., 2017) that includes fermentable carbohydrates, mainly sucrose, present in the diet. However, lactose present in human milk is considered low cariogenic because it is not rapidly fermented by bacteria when compared sucrose (Rugg-Gunn et al., 1985; Birkhed et al., 1993), which is considered the most cariogenic carbohydrate in the diet. The sucrose is the only substrate for extracellular polysaccharide synthesis (Rölla, 1989; Cury et al., 2000). Thus, the increased risk of caries in children with prolonged breastfeeding could be explained by the interaction of a sucrose source in food, associated with continuous exposure to lactose, in which source could be the breast milk during a night breastfeeding. Therefore, evaluating the association of these carbohydrates is important to understand the main cause of increased dental caries in prolonged breastfeeding.

• Casarin, Renato & Petersen, Fernanda Cristina (2019). From colonization to biofilm behavior: a look on severe periodontitis affecting young population.
• Chen, Tsute & Petersen, Fernanda Cristina (2019). The Human Oral Microbiome Database: now extended to comprise the aerodigestive tract.
• Dhariwal, Achal & Petersen, Fernanda Cristina (2019). Visual exploration and network-based analysis of resistome data.
• Federle, Michael & Petersen, Fernanda Cristina (2019). Identifying and exploiting bacterial communication networks to manipulate bacterial pathogens.
• Herredsvela Rørvik, Gro & Petersen, Fernanda Cristina (2019). C-di-AMP signaling in the oral commensal Streptococcus mitis. Show summary

  Abstract: Streptococcus mitis (S. mitis) is an oral commensal that normally lives in harmony with the human host and mainly causes disease in immunocompromised individuals. Cyclic di adenosine monophosphate (c-di-AMP) is a second messenger, relaying environmental signals into cellular responses. C-di-AMP is produced by diadenylate cyclases and broken down by phosphodiesterases. It controls a multitude of traits in different bacteria, for example potassium homeostasis, biofilm formation and sensitivity to antibiotics. This signaling system has been studied in several streptococci, but never in S. mitis. In this project, we characterize this signaling system, and investigate any possible effect that changes in the concentration of c-di-AMP has in S. mitis. Knock out mutants of each of the three genes hypothesised to be involved in c-di-AMP turnover (dacA, pde1 and pde2) were made. Effect of possible roles of c-di-AMP in the control of antibiotic susceptibility, survival under stress, growth under different conditions, metabolism and ability to cause disease are investigated in this project.

• Hu, Duoyi & Petersen, Fernanda Cristina (2019). Strategies for unveiling upstream regulators controlling Streptococcus pneumoniae quorum-sensing. Show summary

  Abstract: Drug-resistant Streptococcus pneumoniae (S. pneumoniae) is still listed as a major threat by Centers for Disease Control and Prevention (CDC) despite vaccine usages. Studies have shown that the Rgg/pheromone quorum sensing system is involved in S. pneumoniae pathogenesis. Finding signals or pathways that control the Rgg quorum-sensing provides us hints to design potential treatments. There are at least eight Rgg paralogs in this species, but most of their functions are unclear. We hypothesize that each of those Rgg paralogs controls a distinct gene regulon and behavior. Using a saturation chromosomal mutagenesis strategy combined with a reporter read-out tool, we hope to identify genes or environmental signals that play a role in controlling Rgg quorum-sensing

• Junges, Roger; Salvadori, Gabriela; Chen, Tsute & Petersen, Fernanda Cristina (2019). Identification of a ComRS-like regulator system in the mitis group of streptococci.
• Laczkovich, Irina & Petersen, Fernanda Cristina (2019). Identification of unannotated pheromone genes by ribosome profiling. Show summary

  Abstract: S. pneumoniae D39 is an opportunistic pathogen found in the human upper respiratory tract. Through a process known as quorum sensing, D39 regulates natural competence, biofilm formation, and production of antimicrobial peptides. Quorum sensing is enacted through the production of small extracellular signaling peptides which bind directly to membrane-located or cytoplasmic receptors. Examples of the latter receptor type (cytoplasmic) are members of the family of proteins called Rgg. To date, eight Rgg paralogs have been identified in D39 but little is understood about their regulatory activities or the behaviors they control. A considerable barrier to understanding Rgg regulation in S. pneumoniae, or any bacterium containing peptide-dependent quorum sensing system, is the lack of appropriate techniques to identify signaling peptides. Peptide pheromones are encoded by small open reading frames (sORFs) that are typically overlooked in annotations of genomes due to their small size. We have performed Retapamulin-enhanced Ribosome profiling (Ribo-RET) to screen genome-wide translation events to identify sORFs and the subset therein that encode pheromones.

• Lam, Trinh & Petersen, Fernanda Cristina (2019). Droplet Confinement of Streptococcus pneumoniae for Studies of Bacterial Genetic Transformation. Show summary

  Abstract: Streptococcus pneumoniae (pneumococcus), a deadly bacterial human pathogen, uses genetic transformation to gain antibiotic resistance. Genetic transformation begins when a pneumococcal strain in a transient specialized physiological state called competence, attacks and lyses another strain, releasing DNA, taking up fragments of the liberated DNA, and integrating divergent genes into its genome. While many steps of the process are known and generally understood, the precise mechanism of this natural genetic transformation is not yet fully understood and current standard strategies to study genetic transformation, which usually employ bulk cultures, fail to identify the donor cells or to capture all descendants from a single productive interaction. To overcome these limitations, we have developed a droplet microfluidic system for isolating individual episodes of bacterial transformation between two confined cells of pneumococcus in 10-m diameter droplets, then recovered all descendants of the interacting competent cell (the survivor) and mapped all resulting recombination events (gene replacements) by whole genome sequencing (WGS). By encapsulating the cells in a 10-μm diameter aqueous droplet, we provide an improved experimental model of genetic transformation, as both participating cells can be identified, and the released DNA is spatially restricted near the attacking strain, allowing characterization of natural genetic transformation during a strictly defined interaction between two confined cells.

• Libardi Pagotto, Leonardo & Petersen, Fernanda Cristina (2019). Inhibition of Streptococcus mutans competence by chlorhexidine gluconate. Show summary

  Abstract: Natural competence is a state that allows Streptococcus mutans to genetically transform by capturing DNA from the environment and incorporating it into its genome. The required machinery depends on the expression of the sigX factor sigma, which can be induced by the competence stimulating peptide (CSP) or the sigX inducing peptide (XIP). Chlorhexidine digluconate (CHX) is commonly used as a mouthwash and could interfere with S. mutans sigX expression, making bacteria more or less able to incorporate DNA from the environment, thus contributing to horizontal gene transfer and acquisition. of bacterial resistance. Therefore, the objective of this study was to evaluate the effect of chlorhexidine digluconate (CHX) on competence activation and genetic transformation of S. mutans. S. mutans isogenic mutants containing luciferase reporter were used in the cipB (CSP activation), sigX and comS (XIP activation) gene promoter, with or without deletion of the comS and comC genes. Cultures were prepared and frozen at optical density (OD600) of 0.5. The cultures were diluted (1:10) and distributed into 96-well plates, followed by the addition of 1 mM D-luciferin, 250 nM CSP or 1μM XIP, and increasing CHX concentrations of 0, 0.25, 0.50 or 1.0 µg/mL. The plates were incubated at 37° C for 12 h in a microplate reader, during which growth (OD600) and cipB or sigX (luminescence) expression were measured every 30 min. Luminescence data were normalized by OD600 values and area under the curve (AUC) calculated. The bacterial transformation test was performed using kanamycin resistance amplicon (aRJ02) which was added after 150, 270 or 390 min of growth. After incubation for 1 h, the suspensions were plated on non-selective (TSB) and selective (TSB + kanamycin at 500 µg/mL) agar medium. Data were analyzed by One-way ANOVA and Tukey Test (α = 5%). Chlorhexidine was able to reduce cipB, sigX and comS expression at all concentrations tested and this was also reflected in the decrease of transformation efficiency in all analyzed times. Under the conditions tested, it can be concluded that chlorhexidine digluconate when used at sub-inhibitory concentrations decreases S. mutans ability to capture exogenous DNA and incorporate it into its genome.

• Martorano Fernandes, Loyse & Petersen, Fernanda Cristina (2019). The role of adhesins of Candida albicans in virulence and pathogenicity of duo-species biofilms with Streptococcus mutans. Show summary

  Abstract: Denture Stomatitis is a biofilm-dependent disease, in which Candida albicans microorganism is prevalent. The interaction between C. albicans and Streptococcus mutans establishes synergistic relationships that contribute to the development of denture stomatitis. The cellular adhesion of C. albicans and S. mutans is physically mediated by cell wall surface adhesins from both organisms. However, the role of C. albicans adhesins in the interaction with S. mutans and the pathogenic potential of this interaction has not been investigated yet. Therefore, this study aims to evaluate the role of C. albicans cell wall adhesins (ALS1 and ALS3) and hyphal wall protein (HWP1) on the formation of C. albicans and S. mutans duo-species biofilms, and to analyze their virulence in contact with, the in vitro model, of oral epithelium. Duo-species biofilms of C. albicans wild-type SC5314 or C. albicans isogenic mutants (ΔALS1, ΔALS3, and ΔHWP1) along with S. mutans UA159 will be grown on surfaces of poly (methyl) methacrylate (PMMA): G1- C. albicans and S. mutans (control group); G2 - C. albicans ΔALS1 and S. mutans; G3 - C. albicans ΔALS3 and S. mutans; G4 - C. albicans ΔHWP1 and S. mutans. After 48h, the biofilms will be collected for the analysis: colony-forming units (CFU)/mL counting, biofilm dry weight quantification, cell metabolism analysis (XTT), biofilm structural analysis by laser confocal microscopy, and analysis of the interaction between the cells by transmission electron microscopy. For the analysis of the virulence/ pathogenicity of biofilms in tissue invasion, cells of C. albicans and S. mutans will be placed in contact with the in vitro model of oral epithelium. The analysis for the tissue invasion will be a. the detection of lactate dehydrogenase (LDH); b. the release of proinflammatory cytokines; c. histological sections stained with hematoxylin and eosin, d. protein blotting analysis, e. gene expression analysis (PCR), and f. visualization of the biofilm on the tissue by confocal microscopy.

• Melo Leite Filho, Ademir & Petersen, Fernanda Cristina (2019). Cariogenic potential of a duo-species biofilm of Streptococcus mutans and Lactobacillus fermentum exposed to lactose. Show summary

  Abstract: Prolonged breastfeeding has been associated to an increased risk of children developing dental caries (Moyniha et al., 2019). That association relies on lactose content in human milk, which can be fermented to acids and could provoke tooth demineralization. However, lactose is not rapidly fermented by most lactic acid bacteria (LAB) present in the biofilm as other carbohydrates present in human diet, due to this, the pH cannot fall until it reaches the critical level. Nonetheless L. fermentum can rapidly ferment lactose due to its constitutive production of β-galactosidases which could increase biofilm cariogenicity (Arukha et al. 2015), and studies have shown that Lactobacillus spp. are prevalent in the biofilm of children with severe early childhood caries (S-ECC), being L. fermentum one of the most frequently isolated species (Caufield et al. 2017). Therefore, the aim of this study is to evaluate the cariogenic potential of a duo-species biofilm of Streptococcus mutans and Lactobacillus fermentum when exposed to lactose.

• Morais Dornelas Figueira, Louise & Petersen, Fernanda Cristina (2019). Streptococcus mitis regulation and genomic sequencing during interaction with Candida albicans. Show summary

  Abstract: Candida spp. are commensal and opportunistic fungus that under predisposing conditions can become pathogenic, leading to the clinical manifestation known as candidiasis. Candida albicans is the most prevalent and pathogenic species among oropharyngeal fungal infections. Studies demonstrated that C. albicans interacts with oral bacteria, mainly from the Streptococcus group, and alters the biofilm composition and virulence. Among the Streptococcus species, it was already showed that Streptococcus mitis can modulate C. albicans biofilm development by inhibiting the fungus filamentation and limiting their growth. Also, S. mitis increased virulence factors of C. albicans by upregulating the expression of important pathogenic-associated fungal genes. It is important to highlight that little is known about C. albicans and S. mitis interaction during cocultures. As biological pathways are structured in a complex genetic network of interactions, elucidating these networks can provide valuable information, such as how microorganisms cause disease and interact with each other, or interspecies. In this context, a recent method determined by the transposon mutagenesis technique associated with next generation RNA sequencing (Tn-seq) has been applied to accurately determine quantitative genetic interactions at genomic scale in microorganisms. Using this methodology in cocultures of S. mitis and C. albicans, it is expected to determine regions of the S. mitis and C. albicans genome that are important for their interaction.

• Morrison, Donald & Petersen, Fernanda Cristina (2019). The oral microbiome: a work in progress.
• Pagotto, LL; Junges, Roger; Salvadori, Gabriela; Petersen, Fernanda Cristina & Ricomoni Filho, Antonio Pedro (2019). Inhibition of Streptococcus mutans competence by chlorhexidine gluconate.
• Pandey, Sushma; Follin-Arbelet, Benoit; Pun, Chin Babadur; Gautam, Dej K.; Johannessen, Anne C.; Petersen, Fernanda Cristina; Costea, Daniela Elena & Sapkota, Dipak (2019). Helicobacter pylori is not present in oral squamous cell carcinomas from cohorts of Norwegian and Nepalese patients.
• Petersen, Fernanda Cristina (2019). Aging in the twilight of antibiotics.
• Petersen, Fernanda Cristina (2019). Mikrobiom og antibiotikaresistens.
• Petersen, Fernanda Cristina (2019). No time to wait: living in the twilight of antibiotics.
• Petersen, Fernanda Cristina (2019). No time to wait: oral research in the twilight of antibiotics.
• Petersen, Fernanda Cristina (2019). Resistance after long term antibiotic treatment.
• Petersen, Fernanda Cristina (2019). Symposium and RESISPART partnership: Norway - Brazil - USA.
• Petersen, Fernanda Cristina & Kolstad, Hilde Zwaig (ed.) (2019). - Har aldri sett så mye snø!.
• Petersen, Fernanda Cristina & Kolstad, Hilde Zwaig (red.) (2019). Gratulerer til Roger Junges som i dag mottok Den norske tannlegeforening sin pris for undervisning og forskning!.
• Petersen, Fernanda Cristina & størseth, inger (ed.) (2019). Resistance after long-term antibiotic treatment.
• Petersen, Fernanda Cristina & størseth, inger (red.) (2019). Utvekslingsopphold i Brasil.
• Petersen, Fernanda Cristina; Torheim, Norunn Kristin & Vistnes, Torunn (red.) (2019). Lysvandring i Botanisk hage: Kommunikasjon mellom bakterier.
• Petersen, Fernanda Cristina & Torwick, Anna (ed.) (2019). Born in the twilight of antibiotics.
• Petersen, Fernanda Cristina & Torwick, Anna (ed.) (2019). Enhancing world-class research and education in biofilm and antibiotic resistance by strengthening cooperation between Norway-Brazil-USA.
• Ricomini, Pedro & Petersen, Fernanda Cristina (2019). Biofilms: a challenging target.
• Rösing, Cassiano Kuchenbecker & Petersen, Fernanda Cristina (2019). Mouthwashes: resistance against oral anti-septics: myth and reality.
• Rued, Britta & Petersen, Fernanda Cristina (2019). Quorum sensing regulates expression of a post-translationally modified peptide in Streptococcus mutans.. Show summary

  Abstract: Streptococcus mutans, an etiological agent of dental caries, is an important human pathogen that can cause systemic diseases such as endocarditis. As such, understanding how it regulates virulence factors is of utmost importance. We are investigating a Rgg quorum sensing system in S. mutans that regulates a small biosynthetic operon. This operon produces a small, ribosomally produced and post-translationally modified peptide (RiPP) molecule termed “WGK” for the unusual Trp-Gly-Lys linkage generated by a radical SAM enzyme. The biological implications of WGK production and its regulation by the Rgg system will be discussed.

• Salvadori, Gabriela & Petersen, Fernanda Cristina (2019). Functional Metagenomics: A Tool to Study Antimicrobial Resistance in Saliva.
• Shekhar, Sudhanshu; Khan, Rabia; Schenck, Karl & Petersen, Fernanda Cristina (2019). Intranasal immunization with the oral commensal Streptococcus mitis induces protection against Streptococcus pneumoniae infection.
• Shekhar, Sudhanshu; Petersen, Fernanda Cristina & Yang, Xi (2019). Editorial: Understanding and Exploiting Host-Commensal Interactions to Combat Pathogens. Frontiers in Immunology.  ISSN 1664-3224. . doi: 10.3389/fimmu.2019.02645
• Tabchoury, Cinthia; Ricomini, Pedro & Petersen, Fernanda Cristina (2019). Welcome to RESISPART symposium.
• Dhariwal, Achal & Petersen, Fernanda Cristina (2018). Network-based analysis of Resistome data.
• Junges, Roger & Petersen, Fernanda Cristina (2018). Eavesdropping on bacterial conversations: what are they doing and do they understand each other?.
• Junges, Roger & Petersen, Fernanda Cristina (2018). Interspecies cell-to-cell communication in the mitis group of streptococci.
• Junges, Roger & Petersen, Fernanda Cristina (2018). Rgg/SHP cross-communication in the mitis group of streptococci.
• Junges, Roger; Petersen, Fernanda Cristina; Egija, Zaura; Lemos, José A. & Merritt, Justin (2018). Environmental and antibiotic stress on oral bacteria: a target for new therapies.
• 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.
• Morrison, Donald A.; Jimenez, Med; Cowley, Lauren A.; Junges, Roger; Petersen, Fernanda Cristina & Hanage, William P. (2018). Genomic signature of natural genetic transformation shared by S. pneumoniae and S. pyogenes.
• Petersen, Fernanda Cristina (2018). Antibiotic stress and bacterial cell-to-cell communication.
• Petersen, Fernanda Cristina (2018). Born in the Twilight of Antibiotics.
• Petersen, Fernanda Cristina (2018, 01. april). Fikk Thon-penger. [Fagblad].  Den Norske Tannlegeforenings Tidende.
• Petersen, Fernanda Cristina (2018, 08. februar). Life Science: Antibiotikaresistens.  Aftenposten.
• Petersen, Fernanda Cristina (2018). Massive Open Online Courses and antimicrobial resistance.
• Petersen, Fernanda Cristina (2018). Projects by the Oslo Group: an overview.
• Petersen, Fernanda Cristina (2018). RESISPART- Inaugural Remarks.
• Petersen, Fernanda Cristina (2018). Streptococcal life.
• Petersen, Fernanda Cristina (2018). The INDNOR project.
• Petersen, Fernanda Cristina (2018). The Oslo group: expertise and tools.
• 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.
• Sturød, Kjersti; Salvadori, Gabriela; Junges, Roger & Petersen, Fernanda Cristina (2018). Antibiotic Induced Streptococcal Competence Not Always Correlate with Transformability.
• Tiainen, Hanna; Wiedmer, David & Petersen, Fernanda Cristina (2018). Biofilm formation and planktonic growth of S. epidermidis in the presence of phenolic compounds tannic acid and pyrogallol.
• Wiedmer, David; Cui, Chen; Petersen, Fernanda Cristina & Tiainen, Hanna (2018). Antibacterial sol-gel coating for bone scaffolds based on the dark catalytic effect of titanium dioxide.
• Cowley, Lauren A.; Petersen, Fernanda Cristina; Junges, Roger; Hanage, William P & Morrison, Donald A. (2017). Co-culture of S. pneumoniae strains fosters large recombination events.
• Cowley, Lauren A.; Petersen, Fernanda Cristina; Junges, Roger; Hanage, William P & Morrison, Donald A. (2017). Large recombination events readily occurring in biofilm cultures of Streptococcus pneumoniae.
• Engen, Stian; Schreurs, Olaf Joseph Franciscus; Petersen, Fernanda Cristina; Blix, Inger Johanne S.; Bækkevold, Espen Sønderaal & Schenck, Karl (2017). Regulation of human monocytes by the oral commensal Streptococcus mitis: a role for PGE2?.
• Gomez-Florit, Manuel; Geissler, Sebastian; Wiedmer, David; Petersen, Fernanda Cristina & Tiainen, Hanna (2017). Multifunctional polyphenol nanocoatings for improved tissue integration of dental implants.
• Junges, Roger; Salvadori, Gabriela; Chen, Tsute; Åmdal, Heidi A.; Jimstan N., Periselneris; Jeremy S., Brown & Petersen, Fernanda Cristina (2017). A bacterial pheromone system regulates biofilm formation and colonization..
• Junges, Roger; Salvadori, Gabriela; Sudhanshu, Shekhar; Åmdal, Heidi A.; Jimstan N., Periselneris; Chen, Tsute; Jeremy S., Brown & Petersen, Fernanda Cristina (2017). An Rgg/SHP quorum sensing system reduces virulence and fitness in Streptococcus pneumoniae.
• Rørvik, Gro Herredsvela; Schreurs, Olaf Joseph Franciscus; Engen, Stian; Blix, Inger Johanne S.; Petersen, Fernanda Cristina & Schenck, Karl (2017). Antibody reactivity to the oral commensal Streptococcus mitis in serum and saliva.
• Salvadori, Gabriela; Junges, Roger & Petersen, Fernanda Cristina (2017). A Competence-Induced Bacteriocin Reduces Growth of Oral Pathogenic Bacteria.
• Salvadori, Gabriela; Junges, Roger; Chen, Tsute & Petersen, Fernanda Cristina (2017). A Competence-Induced Bacteriocin Reduces Growth of Oral Pathogenic Bacteria..
• Salvadori, Gabriela; Junges, Roger; Morrison, Donald A. & Petersen, Fernanda Cristina (2017). High efficiency genetic transformation in encapsulated pneumococcus.

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