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A mutant of Streptococcus pneumoniae that exhibits thermosensitive penicillin tolerance and the paradoxical effect

H H Liu1, A Tomasz

  • 1Rockefeller University, New York, NY 10021.

Journal of General Microbiology
|June 1, 1987
PubMed

Insights

Penicillin-tolerant Streptococcus pneumoniae mutants (Lyt+Tol+) exhibit temperature-dependent lysis. Their tolerance to penicillin is reversed at 37°C, suggesting a thermosensitive regulatory or cell wall structural component.

Area of Science:

  • Microbiology
  • Bacterial Autolysis
  • Streptococcus pneumoniae Pathogenesis

Background:

  • Certain Streptococcus pneumoniae mutants (Lyt+Tol+) display active autolysin but resist penicillin-induced lysis.
  • Understanding the mechanisms of bacterial tolerance to antibiotics is crucial for developing effective treatments.

Purpose of the Study:

  • To investigate the temperature-dependent behavior of Lyt+Tol+ mutants of Streptococcus pneumoniae.
  • To elucidate the underlying mechanisms of penicillin tolerance and lysis in these mutants.

Main Methods:

  • Comparative analysis of Lyt+Tol+ mutants at permissive (32°C) and non-permissive (37°C) temperatures.
  • Penicillin treatment and observation of induced lysis.
  • Temperature shift experiments to assess response dynamics.
  • Enzyme activity assays and synthesis inhibition kinetics.
  • Genetic crosses to determine the genetic basis of thermosensitivity.

Main Results:

  • Lyt+Tol+ mutants showed temperature-dependent penicillin-induced lysis, with lysis occurring at 37°C but not at 32°C.
  • Mutants exhibited a 'paradoxical response' to penicillin at the lysis-permissive temperature.
  • Temperature shift experiments revealed rapid transitions between tolerant and lytic states.
  • No significant differences in autolysin activity or synthesis inhibition kinetics were observed between temperatures.
  • Genetic analysis indicated that thermosensitivity resides outside the autolytic enzyme itself.

Conclusions:

  • The thermosensitivity of penicillin-induced autolysis in Lyt+Tol+ mutants is not due to the autolysin enzyme.
  • The findings suggest a thermosensitive regulatory step in autolysin function or alterations in cell wall structure at different temperatures are responsible for the observed phenotype.

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