Effect of Stx2-encoding phage on the motility and gene expression involved in moving of Escherichia coli lysogen

Abstract:

Abstract:［Objective］The effect of flhDC，fliA，fliD and fliE genes involved in moving of Escherichia coli (E.coli) on the motility of lysogened strain by Stx2-encoding phage ΦMin27 was explored by gene knockout and phage lysogenic conversion．［Methods］ Using the lambda Ｒed recombinase system，the mutant strains of E.coli MG1655 named MG1655 △flhDC，MG1655 △fliA，MG1655 △fliD and MG1655 △fliE were constructed． Then the corresponding complemented strains by ligating amplified targeted genes into the low copy vector pUC18 at the BamHI and HindⅢ sites and transforming these plasmids into mutant strains were acquired． By lysogenic infection of Stx2-encoding phage ФMin27，the lysogens for mutants named MG1655△flhDCФMin27，MG1655△fliAФMin27，MG1655△fliDФMin27 and MG1655△fliEФMin27 were achieved． Subsequently，the motility of wild strain，the mutants，the complemented strains and the lysogens were detected． The changes of expression of the other genes involved in motility between wild strain and the lysogens before and after flhDC deletion by qＲT-PCＲ were analyzed．［Results］Lysogenic infection of Stx2-encoding phage ФMin27 could promote the expression of fliA and fliD gene and enhance the motility of MG1655．For flhDC deletion，higher expression of fliA and fliD gene of MG1655 appeared，but the motility had no change．However，lysogen for MG1655△flhDC lost the swimming motility．By gene transcriptional level detection，the expression of fliA and fliD gene of MG1655 △flhDCФMin27 was down-regulated significantly compared with MG1655 △flhDC，and no marked variation was observed for fliE gene． The single deletion of fliA，fliD and fliE gene had no effect on the motility of E.coli MG1655 and lysogened strain by Stx2-encoding phage ФMin27.［Conclusion］The results show that fliA and fliD gene together participated the regulation for flagella motility and flhDC gene could affect the motility of the lysogened strain by phage．It provides the theoretical basis for further research on the mutual regulation between phage lysogenization and host genes.

Key words:Keywords: Escherichia coli，Stx2-encoding phage，lysogen，flhDC，motility