Transcriptional Response of Enterococcus faecalis to Oxygen and Nutrient Availability in Mucus-Relevant Conditions

This RNA-seq study investigates the transcriptional response of Enterococcus faecalis ATCC 19433 to varying oxygen and nutrient conditions relevant to mucosal environments. Cultures were grown in YCFA basal broth (pH 6.8-7) under four conditions: no sugars, mucus (1 mg per mL), mucus plus 0.5% glucose, and 0.5% glucose, under both anaerobic and aerobic environments, with biological triplicates. RNA was extracted using the RNeasy PowerMicrobiome Kit (Qiagen), and RNA integrity was confirmed by fragment analysis. Sequencing libraries were prepared and sequenced by Novogene. Reads were aligned to the E. faecalis ATCC 19433 genome using Bowtie2, and differential expression was analyzed with DESeq2 (padj < 0.05). Functional annotation was performed using UniRef90 and UniProt databases. GO enrichment analysis excluded housekeeping pathways and used the ATCC 19433 genome as the background.Results revealed oxygen exposure induced mucus degradation and upregulation of gelatinase, matrixin, and serine proteases. In anaerobic, mucus-only conditions, E. faecalis upregulated surface adhesion proteins, including collagen- and fibrinogen-binding proteins. Under anaerobic conditions with both mucus and glucose, glycosyltransferases and biofilm-associated pili were upregulated, coinciding with preserved mucus integrity. These findings highlight E. faecalis's metabolic adaptability and its regulation of virulence in response to nutrient and oxygen availability.