Expression of fljB: z66 on a linear plasmid of Salmonella enterica serovar typhi is dependent on FliA and FlhDC and regulated by OmpR

• Main Authors: Shungao Xu, Xin Zou, Xiumei Sheng, Haifang Zhang, Lingxiang Mao, Hong Du, Huaxi Xu, Xinxiang Huang
• Format: Article
• Language: English
• Published: Sociedade Brasileira de Microbiologia 2010-10-01
• Series: Brazilian Journal of Microbiology
• Subjects: Salmonella enterica serovar Typhi; fljB:z66; flhDC; fliA; ompR
• Online Access: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1517-83822010000300025
• ISSN: 1517-8382; 1678-4405

Salmonella enterica serovar Typhi z66-positive strains have two different flagellin genes, fliC:d/j and fljB:z66, located on the chromosome and on a linear plasmid, respectively. To investigate the mechanism underlying the expressional regulation of fljB:z66, gene deletion mutants of the regulators FliA, FlhDC, and OmpR were constructed in this study. The expression levels of fliC and fljB:z66 were analyzed by qRT-PCR in the wild-type strain and mutants at high and low osmolarity. The results show that the expression levels of both fljB:z66 and fliC were greatly reduced in fliA and flhDC mutants under both high and low osmotic conditions. In the ompR mutant, the expression levels of fljB:z66, fliC, fliA, and flhD were increased at low osmotic conditions. SDS-PAGE and western blotting analysis of the secreted proteins revealed that the FljB:z66 was almost absent in the fliA and flhDC mutants at both high and low osmolarity. In the wild-type strain, the fljB:z66 was more highly expressed under high-osmolarity conditions than under low-osmolarity conditions. However, this difference in expression disappeared in the ompR mutant. Translational expression assay of FljB:z66 showed that the FljB:z66 expression was decreased in ompR mutant at both low and high osmolarity. These results suggest that the expression of fljB:z66 in S. enterica serovar Typhi is dependent on FliA and FlihDC, and OmpR can regulate the expression and secretion of FljB:z66 in different osmolarity.