AUTHOR=Du Yanli , Wang Xiangyu , Han Zongli , Hua Ying , Yan Kaina , Zhang Bao , Zhao Wei , Wan Chengsong 

TITLE=Polyphosphate Kinase 1 Is a Pathogenesis Determinant in Enterohemorrhagic Escherichia coli O157:H7

JOURNAL=Frontiers in Microbiology

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2021.762171

DOI=10.3389/fmicb.2021.762171

ISSN=1664-302X

ABSTRACT=<p>The <italic>ppk1</italic> gene encodes polyphosphate kinase (PPK1), which is the major catalytic enzyme that <italic>Escherichia coli</italic> utilizes to synthesize inorganic polyphosphate (polyP). The aim of this study was to explore the role of PPK1 in the pathogenesis of Enterohemorrhagic <italic>E. coli</italic> O157:H7 (EHEC O157:H7). An isogenic in-frame <italic>ppk1</italic> deletion mutant (Δ<italic>ppk1</italic>) and <italic>ppk1</italic> complemented mutant (<italic>Cppk1</italic>) were constructed and characterized in comparison to wild-type (WT) EHEC O157:H7 strain EDL933w by microscope observation and growth curve analysis. Survival rates under heat stress and acid tolerance, both of which the bacteria would face during pathogenesis, were compared among the three strains. LoVo cells and a murine model of intestinal colitis were used as the <italic>in vitro</italic> and <italic>in vivo</italic> models, respectively, to evaluate the effect of PPK1 on adhesion and invasion during the process of pathogenesis. Real-time reverse-transcription PCR of regulatory gene <italic>rpoS</italic>, adhesion gene <italic>eae</italic>, and toxin genes <italic>stx1</italic> and <italic>stx2</italic> was carried out to corroborate the results from the <italic>in vitro</italic> and <italic>in vivo</italic> models. The <italic>ppk1</italic> deletion mutant exhibited disrupted polyP levels, but not morphology and growth characteristics. The survival rate of the Δ<italic>ppk1</italic> strain under stringent environmental conditions was lower as compared with WT and <italic>Cppk1.</italic> The <italic>in vitro</italic> assays showed that deletion of the <italic>ppk1</italic> gene reduced the adhesion, formation of attaching and effacing (A/E) lesions, and invasive ability of EHEC O157:H7. Moreover, the virulence of the Δ<italic>ppk1</italic> in BALB/c mice was weaker as compared with the other two strains. Additionally, mRNA expression of <italic>rpoS</italic>, <italic>eae</italic>, <italic>stx1</italic> and <italic>stx2</italic> were consistent with the <italic>in vitro</italic> and <italic>in vivo</italic> results. In conclusion: EHEC O157:H7 requires PPK1 for both survival under harsh environmental conditions and virulence <italic>in vivo</italic>.</p>