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Restrictive Streptomycin Resistance Mutations Decrease the Formation of Attaching and Effacing Lesions in Escherichia

Chun Chen1, Carla A Blumentritt2, Meredith M Curtis3

  • 1Department of Food Science, the Penn State University, University Park, Pennsylvania, USA.

Antimicrobial Agents and Chemotherapy
|June 26, 2013
PubMed

Insights

Streptomycin resistance mutations in E. coli O157:H7 can impair the type III secretion system (T3SS) essential for intestinal colonization. Nonrestrictive mutations are better for studying wild-type bacterial behavior.

Area of Science:

  • Microbiology
  • Bacterial Genetics
  • Pathogenesis

Background:

  • Streptomycin resistance (StrR) mutations in ribosomal protein S12 affect bacterial translation accuracy and speed.
  • Escherichia coli O157:H7 utilizes the locus of enterocyte effacement (LEE) and its type III secretion system (T3SS) for intestinal adhesion and effacement.
  • StrR mutants are often used as selective markers in bacterial studies, but their physiological impact requires careful evaluation.

Purpose of the Study:

  • To investigate the impact of StrR mutations in E. coli O157:H7 on the expression and secretion of T3SS effector proteins.
  • To assess how different S12 mutations (restrictive vs. nonrestrictive) influence the formation of attaching and effacing lesions.
  • To determine the suitability of StrR mutants as surrogates for wild-type E. coli O157:H7 in experimental settings.

Main Methods:

  • Generation of spontaneous StrR mutants of E. coli O157:H7 with specific mutations in ribosomal protein S12 (K42T, K42I, K87R, K42R).
  • Quantification of T3SS translocated proteins EspA and EspB expression and secretion levels.
  • Adherence assays and actin staining to evaluate the formation of attaching and effacing lesions.

Main Results:

  • Restrictive S12 mutations (K42T, K42I) significantly decreased EspA and EspB expression and secretion.
  • Mildly restrictive (K87R) and nonrestrictive (K42R) mutations had minimal or no significant effect on EspA and EspB secretion.
  • Restrictive mutations compromised the ability of E. coli O157:H7 to form attaching and effacing lesions.

Conclusions:

  • StrR mutations in E. coli O157:H7 can negatively impact T3SS function and virulence phenotypes.
  • Careful characterization of StrR mutants is crucial before employing them in in vivo or in vitro studies of LEE-directed phenotypes.
  • Nonrestrictive mutants, like K42R, serve as more reliable surrogates for wild-type E. coli O157:H7 compared to restrictive mutants.

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