title: Genome-wide identification of genes essential for the survival of Streptococcus pneumoniae in human saliva.
abstract: Since Streptococcus pneumoniae transmits through droplet spread, this respiratory tract pathogen may be able to survive in saliva. Here, we show that saliva supports survival of clinically relevant S. pneumoniae strains for more than 24 h in a capsule-independent manner. Moreover, saliva induced growth of S. pneumoniae in growth-permissive conditions, suggesting that S. pneumoniae is well adapted for uptake of nutrients from this bodily fluid. By using Tn-seq, a method for genome-wide negative selection screening, we identified 147 genes potentially required for growth and survival of S. pneumoniae in saliva, among which genes predicted to be involved in cell envelope biosynthesis, cell transport, amino acid metabolism, and stress response predominated. The Tn-seq findings were validated by testing a panel of directed gene deletion mutants for their ability to survive in saliva under two testing conditions: at room temperature without CO2, representing transmission, and at 37 °C with CO2, representing in-host carriage. These validation experiments confirmed that the plsX gene and the amiACDEF and aroDEBC operons, involved in respectively fatty acid metabolism, oligopeptide transport, and biosynthesis of aromatic amino acids play an important role in the growth and survival of S. pneumoniae in saliva at 37 °C. In conclusion, this study shows that S. pneumoniae is well-adapted for growth and survival in human saliva and provides a genome-wide list of genes potentially involved in adaptation. This notion supports earlier evidence that S. pneumoniae can use human saliva as a vector for transmission.
authors.affiliation: Laboratory of Pediatric Infectious Diseases, Department of Pediatrics, Radboud University Medical Centre, Nijmegen, the Netherlands.
authors.forename: Lilly M
authors.initials: LM
authors.lastname: Verhagen
authors.affiliation: Laboratory of Pediatric Infectious Diseases, Department of Pediatrics, Radboud University Medical Centre, Nijmegen, the Netherlands.
authors.forename: Marien I
authors.initials: MI
authors.lastname: de Jonge
authors.affiliation: Laboratory of Pediatric Infectious Diseases, Department of Pediatrics, Radboud University Medical Centre, Nijmegen, the Netherlands.
authors.forename: Peter
authors.initials: P
authors.lastname: Burghout
authors.affiliation: Laboratory of Pediatric Infectious Diseases, Department of Pediatrics, Radboud University Medical Centre, Nijmegen, the Netherlands.
authors.forename: Kiki
authors.initials: K
authors.lastname: Schraa
authors.affiliation: Laboratory of Pediatric Infectious Diseases, Department of Pediatrics, Radboud University Medical Centre, Nijmegen, the Netherlands.
authors.forename: Lorenza
authors.initials: L
authors.lastname: Spagnuolo
authors.affiliation: Laboratory of Pediatric Infectious Diseases, Department of Pediatrics, Radboud University Medical Centre, Nijmegen, the Netherlands.
authors.forename: Svenja
authors.initials: S
authors.lastname: Mennens
authors.affiliation: Laboratory of Pediatric Infectious Diseases, Department of Pediatrics, Radboud University Medical Centre, Nijmegen, the Netherlands.
authors.forename: Marc J
authors.initials: MJ
authors.lastname: Eleveld
authors.affiliation: Laboratory of Pediatric Infectious Diseases, Department of Pediatrics, Radboud University Medical Centre, Nijmegen, the Netherlands.
authors.forename: Christa E
authors.initials: CE
authors.lastname: van der Gaast-de Jongh
authors.affiliation: Laboratory of Pediatric Infectious Diseases, Department of Pediatrics, Radboud University Medical Centre, Nijmegen, the Netherlands ; Centre for Molecular and Biomolecular Informatics, Nijmegen Centre for Molecular Life Sciences, Radboud University Medical Centre, Nijmegen, the Netherlands.
authors.forename: Aldert
authors.initials: A
authors.lastname: Zomer
authors.affiliation: Laboratory of Pediatric Infectious Diseases, Department of Pediatrics, Radboud University Medical Centre, Nijmegen, the Netherlands.
authors.forename: Peter W M
authors.initials: PW
authors.lastname: Hermans
authors.affiliation: Laboratory of Pediatric Infectious Diseases, Department of Pediatrics, Radboud University Medical Centre, Nijmegen, the Netherlands.
authors.forename: Hester J
authors.initials: HJ
authors.lastname: Bootsma
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial; D016680:Genome, Bacterial / Q000235:genetics*; D006801:Humans; D011008:Pneumococcal Infections / Q000235:genetics* / Q000382:microbiology / Q000401:mortality*; D012463:Saliva / Q000382:microbiology*; D013296:Streptococcus pneumoniae / Q000235:genetics / Q000254:growth & development* / Q000472:pathogenicity; D015996:Survival Rate
chemical_list: D001426:Bacterial Proteins