The role of uspE in virulence and biofilm formation by Histophilus somni.

ABSTRACT

UspE is a global regulator in Escherichia coli. To study the function of Histophilus somni uspE, strain 2336TnuspE was identified from a bank of mutants generated with EZTn5™ Tnp Transposome™ that were biofilm deficient. The 2336TnuspE mutant was highly attenuated in mice, the electrophoretic profile of its lipooligosaccharide (LOS) indicated the LOS was truncated, and the mutant was significantly more serum-sensitive compared to the wildtype strain. In addition to forming a deficient biofilm, exopolysaccharide (EPS) production was also compromised, but the electrophoretic profile of outer membrane proteins was not altered. RNA sequence analysis revealed that the transcription levels of some stress response chaperones, transport proteins, and a large number of ribosomal protein genes in 2336TnuspE were significantly differentially regulated compared to strain 2336. Therefore, uspE may differentially function in direct and indirect expression of H. somni genes, but its attenuation may be linked to poor biofilm formation and rapid clearance of the bacteria resulting from a compromised LOS structure. Our results support that uspE is a global stress regulatory gene in H. somni.