sRNA molecules participate in hyperosmotic stress response regulation in Sphingomonas melonis TY.

Drought and salinity are ubiquitous environmental factors that pose hyperosmotic threats to microorganisms and impair their efficiency in performing environmental functions. However, bacteria have developed various responses and regulatory systems to cope with these abiotic challenges. Posttranscriptional regulation plays vital roles in regulating gene expression and cellular homeostasis, as hyperosmotic stress conditions can lead to the induction of specific small RNA molecules (sRNAs) that participate in stress response regulation. Here, we report a candidate functional sRNA landscape of Sphingomonas melonis TY under hyperosmotic stress, and 18 sRNAs were found with a clear response to hyperosmotic stress. These findings will help in the comprehensive analysis of sRNA regulation in Sphingomonas species. Weighted correlation network analysis revealed a 263 nucleotide sRNA, SNC251, which was transcribed from its own promoter and showed the most significant correlation with hyperosmotic response factors. Deletion of snc251 affected biofilm formation and multiple cellular processes, including ribosome-related pathways, aromatic compound degradation, and the nicotine degradation capacity of S. melonis TY, while overexpression of SNC251 facilitated biofilm formation by TY under hyperosmotic stress. Two genes involved in the TonB system were further verified to be activated by SNC251, which also indicated that SNC251 is a trans -acting sRNA. Briefly, this research reports a landscape of sRNAs participating in the hyperosmotic stress response in S. melonis and reveals a novel sRNA, SNC251, which contributes to the S. melonis TY biofilm formation and thus enhances its hyperosmotic stress response ability.IMPORTANCE Sphingomonas species play a vital role in plant defense and pollutant degradation and survive extensively under drought or salinity. Previous studies have focused on the transcriptional and translational responses of Sphingomonas under hyperosmotic stress, but the posttranscriptional regulation of small RNA molecules (sRNAs) is also crucial for quickly modulating cellular processes to adapt dynamically to osmotic environments. In addition, the current knowledge of sRNAs in Sphingomonas is extremely scarce. This research revealed a novel sRNA landscape of Sphingomonas melonis and will greatly enhance our understanding of sRNAs' acting mechanisms in the hyperosmotic stress response.