Many putative sRNAs have been characterized using bioinformatic analysis and high-throughput sequencing in Gram-positive Bacillus strains, but there are only a few functional studies on the sRNAs involved in the spore formation developmental process. In particular, there is no sRNA confirmed experimentally to regulate the late stages of sporulation. Bvs196 is an sRNA with a length of 294 nucleotides that is abundantly expressed in the stationary phase of several media and independently transcribed in Bacillus velezensis strain PEBA20, as validated by RNA-seq and Northern blot,. It is also confirmed, by qRT-PCR, that Bvs196 is transcribed abundantly throughout the intermediate and late stages of sporulation. Using the gfpmut3a gene transcriptional reporter demonstrates that Bvs196 is expressed specifically in the forespore during sporulation and controlled by σ^F and σ^G (mainly by σ^G). This was observed by fluorescence microscopy and multi-function microplate reader. Further evolutionary conservation analysis found that Bvs196 is widely present in Bacillus with a strongly conserved and stable secondary structure. Resistance phenotypic assays of spores formed from the Bvs196 deletion mutant, the overexpressed Bvs196 mutant, and the wild-type strain revealed that the absence of Bvs196 led to reduced heat and UV resistance and enhanced formaldehyde resistance. We determined, by MST analysis, that Bvs196 can directly interact with spo0A and sspN-tlp mRNAs in vitro, and that short incomplete complementary paired bases affect the binding affinity of Bvs196 to target mRNAs. Our results suggest that Bvs196 is a novel sporulation-specific sRNA of B. velezensis, 294 nt in length, independently transcribed under the control of σ^F and σ^G in the forespore during sporulation, and that it affects spore resistance, and is able to directly interact with spo0A and sspN-tlp mRNAs. The remarkable conservation and impressive expression level of Bvs196 imply that it acts as an important conservative regulator, presumably by interacting with many other unknown targets in the forespore, and therefore contributing to spore properties. This work provides new clues for further understanding of the spore formation regulatory network.

During their growth, bacteria respond to complex environmental changes through equally com-plex and orderly regulatory mechanisms. sRNA has an important role as a post-transcriptional regulator in the environmental adaptation of Bacillus. In this study, we identified an sRNA Bvs091 located in the intergenic region of the Bacillus velezensis, which is widely present in the genus Bacillus and whose expression is upregulated by salt treatment. The deletion of bvs091 in B. ve-lezensis PEBA20 led to a reduced growth rate and a change in the phenotypes, with simple colony structures and low and easily degradable biofilm. Salt tolerance tests indicated that the deletion of bvs091 results in a reduced salt tolerance. galT2 mRNA is supposed to be a direct target of Bvs091 according to results obtained by using the bioinformatic method and performing qRT-PCR analysis. The microscale thermophoresis (MST) analysis showed that Bvs091 could directly bind 28‒51 bases in front of the promoter of galT2. Subsequently, the deletion of galT2 in B. velezensis resulted in increased salt tolerance. Based on the techniques of double plasmids and a half-life period, sRNA Bvs091 is confirmed as a trans-encoded sRNA that negatively regulates the mRNA expression of galT2. In brief, the trans-encoded sRNA Bvs091 acts by pairing the incomplete complementary bases of galT2 mRNA, reducing galT2 mRNA’s stability and affecting the trans-lation efficiency.