AUTHOR=Bastakoti Srijana , Pesonen Maiju , Ajayi Clement , Julin Kjersti , Corander Jukka , Johannessen Mona , Hanssen Anne-Merethe 

TITLE=Co-culturing with Streptococcus anginosus alters Staphylococcus aureus transcriptome when exposed to tonsillar cells

JOURNAL=Frontiers in Cellular and Infection Microbiology

VOLUME=14

YEAR=2024

URL=https://www.frontiersin.org/journals/cellular-and-infection-microbiology/articles/10.3389/fcimb.2024.1326730

DOI=10.3389/fcimb.2024.1326730

ISSN=2235-2988

ABSTRACT=<sec><title>Introduction</title><p>Improved understanding of <italic>Staphylococcus aureus</italic> throat colonization in the presence of other co-existing microbes is important for mapping <italic>S. aureus</italic> adaptation to the human throat, and recurrence of infection. Here, we explore the responses triggered by the encounter between two common throat bacteria, <italic>S. aureus</italic> and <italic>Streptococcus anginosus</italic>, to identify genes in <italic>S. aureus</italic> that are important for colonization in the presence of human tonsillar epithelial cells and <italic>S. anginosus</italic>, and further compare this transcriptome with the genes expressed in <italic>S. aureus</italic> as only bacterium.</p></sec><sec><title>Methods</title><p>We performed an <italic>in vitro</italic> co-culture experiment followed by RNA sequencing to identify interaction-induced transcriptional alterations and differentially expressed genes (DEGs), followed by gene enrichment analysis.</p></sec><sec><title>Results and discussion</title><p>A total of 332 and 279 significantly differentially expressed genes with p-value &lt; 0.05 and log<sub>2</sub> FoldChange (log<sub>2</sub>FC) ≥ |2| were identified in <italic>S. aureus</italic> after 1 h and 3 h co-culturing, respectively. Alterations in expression of various <italic>S. aureus</italic> survival factors were observed when co-cultured with <italic>S. anginosus</italic> and tonsillar cells. The serine-aspartate repeat-containing protein D (<italic>sdrD</italic>) involved in adhesion, was for example highly upregulated in <italic>S. aureus</italic> during co-culturing with <italic>S. anginosus</italic> compared to <italic>S. aureus</italic> grown in the absence of <italic>S. anginosus</italic>, especially at 3 h. Several virulence genes encoding secreted proteins were also highly upregulated only when <italic>S. aureus</italic> was co-cultured with <italic>S. anginosus</italic> and tonsillar cells, and iron does not appear to be a limiting factor in this environment. These findings may be useful for the development of interventions against <italic>S. aureus</italic> throat colonization and could be further investigated to decipher the roles of the identified genes in the host immune response in context of a throat commensal landscape.</p></sec>