Co-culturing with alters transcriptome when exposed to tonsillar cells.

Introduction: Improved understanding of throat colonization in the presence of other co-existing microbes is important for mapping adaptation to the human throat, and recurrence of infection. Here, we explore the responses triggered by the encounter between two common throat bacteria, and , to identify genes in that are important for colonization in the presence of human tonsillar epithelial cells and , and further compare this transcriptome with the genes expressed in as only bacterium.

Methods: We performed an co-culture experiment followed by RNA sequencing to identify interaction-induced transcriptional alterations and differentially expressed genes (DEGs), followed by gene enrichment analysis.

Results And Discussion: A total of 332 and 279 significantly differentially expressed genes with p-value < 0.05 and log FoldChange (logFC) ≥ |2| were identified in after 1 h and 3 h co-culturing, respectively. Alterations in expression of various survival factors were observed when co-cultured with and tonsillar cells. The serine-aspartate repeat-containing protein D () involved in adhesion, was for example highly upregulated in during co-culturing with compared to grown in the absence of , especially at 3 h. Several virulence genes encoding secreted proteins were also highly upregulated only when was co-cultured with 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 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.