Three new serine-protease autotransporters of Enterobacteriaceae (SPATEs) from extra-intestinal pathogenic Escherichia coli and combined role of SPATEs for cytotoxicity and colonization of the mouse kidney

Virulence. 2019 Dec;10(1):568-587. doi: 10.1080/21505594.2019.1624102.


Serine protease autotransporters of Enterobacteriaceae (SPATEs) are secreted proteins that contribute to virulence and function as proteases, toxins, adhesins, and/or immunomodulators. An extra-intestinal pathogenic E. coli (ExPEC) O1:K1 strain, QT598, isolated from a turkey, was shown to contain vat, tsh, and three uncharacterized SPATE-encoding genes. Uncharacterized SPATEs: Sha (Serine-protease hemagglutinin autotransporter), TagB and TagC (tandem autotransporter genes B and C) were tested for activities including hemagglutination, autoaggregation, and cytotoxicity when expressed in E. coli K-12. Sha and TagB conferred autoaggregation and hemagglutination activities. TagB, TagC, and Sha all exhibited cytopathic effects on a bladder epithelial cell line. In QT598, tagB and tagC are tandemly encoded on a genomic island, and were present in 10% of UTI isolates and 4.7% of avian E. coli. Sha is encoded on a virulence plasmid and was present in 1% of UTI isolates and 20% of avian E. coli. To specifically examine the role of SPATEs for infection, the 5 SPATE genes were deleted from strain QT598 and tested for cytotoxicity. Loss of all five SPATEs abrogated the cytopathic effect on bladder epithelial cells, although derivatives producing any of the 5 SPATEs retained cytopathic activity. In mouse infections, sha gene-expression was up-regulated a mean of sixfold in the bladder compared to growth in vitro. Loss of either tagBC or sha did not reduce urinary tract colonization. Deletion of all 5 SPATEs, however, significantly reduced competitive colonization of the kidney supporting a cumulative role of SPATEs for QT598 in the mouse UTI model.

Keywords: Autotransporters; SPATE; Toxins; avian pathogenic; mouse infection; poultry; serine protease autotransporter; uropathogenic.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Bacterial Toxins / metabolism
  • Cell Line
  • Escherichia coli Infections / microbiology
  • Extraintestinal Pathogenic Escherichia coli / genetics*
  • Extraintestinal Pathogenic Escherichia coli / pathogenicity
  • Female
  • Genome, Bacterial
  • Humans
  • Kidney / microbiology*
  • Mice
  • Phylogeny
  • Serine Proteases / genetics
  • Serine Proteases / metabolism*
  • Type V Secretion Systems / genetics
  • Type V Secretion Systems / metabolism*
  • Urinary Tract / microbiology
  • Virulence


  • Bacterial Toxins
  • Type V Secretion Systems
  • Serine Proteases

Grant support

This work was supported by the Institut Pasteur [ACIP]; Natural Sciences and Engineering Research Council of Canada [2014-06622] and [2019-06642].