The effects of PstR, a PadR family transcriptional regulatory factor, in Plesiomonas shigelloides are revealed by transcriptomics

Background: Plesiomonas shigelloides is a gram-negative opportunistic pathogen associated with gastrointestinal and extraintestinal diseases in humans. There have been reports of specific functional genes in the study of P. shigelloides , but there are also many unknown genes that may play a role in P. shigelloides pathogenesis as global regulatory proteins or virulence factors. Results: In this study, we found a transcriptional regulator of the PadR family in P. shigelloides and named it PstR (GenBank accession number: EON87311.1), which is present in various pathogenic bacteria but whose function has rarely been reported. RNA sequencing (RNA-Seq) was used to analyze the effects of PstR on P. shigelloides , and the results indicated that PstR regulates approximately 9.83% of the transcriptome, which includes impacts on motility, virulence, and physiological metabolism. RNA-seq results showed that PstR positively regulated the expression of the flagella gene cluster, which was also confirmed by quantitative Real-Time Polymerase Chain Reaction (qRT-PCR) and lux assays. Meanwhile, the Δ pstR mutant strains lacked flagella and were non-motile, as confirmed by motility assays and transmission electron microscopy (TEM). Additionally, RNA-seq, qRT-PCR, and lux assays demonstrated that PstR also positively regulates T3SS expression, which aids in P. shigelloides ' capacity to infect Caco-2 cells. Meanwhile, we also revealed that PstR negatively regulates fatty acid degradation and metabolism, as well as the regulatory relationship between PsrA, a regulator of fatty acid degradation and metabolism, and its downstream genes in P. shigelloides . Conclusions: Overall, we revealed the effects of PstR on motility, virulence, and physiological metabolism in P. shigelloides , which will serve as a foundation for future research into the intricate regulatory network of PstR in bacteria.