Reading between the Lines: Utilizing RNA-Seq Data for Global Analysis of sRNAs in Staphylococcus aureus

Area of Science:

• Microbiology
• Genomics
• Molecular Biology

Background:

• Regulatory small RNAs (sRNAs) are crucial for bacterial gene regulation but are often missing from standard genome annotations.
• This omission leads to the underestimation of sRNA roles in pathogens like *Staphylococcus aureus*.
• Previous work established an updated *S. aureus* USA300 genome annotation file including 303 known sRNAs.

Purpose of the Study:

• To re-evaluate publicly available RNA-Seq datasets using an updated *S. aureus* genome annotation.
• To recover and analyze previously overlooked data on sRNA expression, stability, and potential peptide-encoding capabilities.
• To identify sRNAs with potential roles in *in vivo* conditions, such as cystic fibrosis lung and vaginal colonization.

Main Methods:

• Utilized an updated *S. aureus* genome annotation file with 303 sRNAs.
• Reanalyzed transcriptomic data from 22 studies across 64 conditions to assess sRNA expression.
• Applied RNA stability assays and ribosome profiling (Ribo-seq) to determine sRNA stability and peptide-encoding potential.
• Examined *in vivo* RNA-Seq data from cystic fibrosis lung and murine vaginal colonization models.

Main Results:

• Expression profiles of 303 sRNAs were characterized across diverse experimental conditions.
• Identified highly stable and unstable sRNAs.
• Discovered sRNAs with the potential to encode peptides, experimentally confirming three such peptides, including one at the *tsr37* locus influencing autoaggregation.
• Identified 29 sRNAs potentially active *in vivo* in CF lung and vaginal colonization models.

Conclusions:

• Reanalysis of existing data with updated annotations significantly enhances understanding of *S. aureus* sRNAs.
• Highlights the functional importance of specific sRNAs, including the *tsr37*-encoded peptide in autoaggregation.
• Underscores the necessity for continuous curation and updating of bacterial genome annotation files for comprehensive analysis.
• Identified novel sRNAs with potential roles in *in vivo* pathogenesis.