Driving the expression of theSalmonella entericasv Typhimurium flagellum usingflhDCfromEscherichia coliresults in key regulatory and cellular differences

Abstract

ABSTRACTThe flagellar systems ofEscherichia coliandSalmonella entericaexhibit a significant level of genetic and functional synteny. Both systems are controlled by the flagellar specific master regulator FlhD4C2. Since the early days of genetic analyses of flagellar systems it has been known thatE. coli flhDCcan complement a ΔflhDCmutant inS. enterica. The genomic revolution has identified how genetic changes to transcription factors and / or DNA binding sites can impact the phenotypic outcome across related species. We were therefore interested in asking: using modern tools to interrogate flagellar gene expression and assembly, what would the impact be of replacing theflhDCcoding sequences inS. entericafor theE. coligenes at theflhDC S. enterciachromosomal locus? We show that even though all strains created are motile, flagellar gene expression is measurably lower whenflhDCECare present. These changes can be attributed to the impact of FlhD4C2DNA recognition and the protein-protein interactions required to generate a stable FlhD4C2complex. Furthermore, our data suggests that inE. colithe internal flagellar FliT regulatory feedback loop has a marked difference with respect to output of the flagellar systems. We argue due diligence is required in making assumptions based on heterologous expression of regulators and that even systems showing significant synteny may not behave in exactly the same manner.