Deletion of the genes waaC, waaF, or waaG in Escherichia coli W3110 disables the flagella biosynthesis

Flagella assembly was investigated in the Escherichia coli W3110 wild-type strain and ΔwaaF, ΔwaaC, and ΔwaaG mutant strains that only synthesize lipopolysaccharide with different lengths, using transmission electron microscopy and whole genome transcriptome profiling. Under the electron microscope, the flagella were observed on the cell surface of the W3110 strain but not the ΔwaaC, ΔwaaF, or ΔwaaG strains. Transcriptional profiling showed that 1382 genes in ΔwaaC, 526 genes in ΔwaaF, and 965genes in ΔwaaG were significantly regulated compared to the control W3110 strain. These genes were further analyzed by gene ontology and KEGG pathway. Although there were significant transcriptional differences among the ΔwaaC, ΔwaaF, and ΔwaaG strains, genes related to flagella assembly and bacterial chemotaxis (the linkage between the flagella and the environment) were significantly down-regulated in all three strains. The data demonstrated that flagella assembly in E. coli depends on the length of lipopolysaccharide.