ISSN:
1365-2958
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Biology
,
Medicine
Notes:
The role of recA in Lactococcus lactis, a microaerophilic fermenting organism, was examined by constructing a recA-disrupted strain. This single alteration had a surprisingly pleiotropic effect. In addition to its roles in homologous recombination and DNA repair, recA is also involved in responses to oxygen and heat stresses. We found that oxygen stress induced by aeration causes reductions in growth and stationary-phase survival of the recA strain. Toxicity is a consequence of hydroxyl radical production via the Fenton Reaction and is alleviated by catalase or Ferrozine addition. These results suggest that oxygen radicals are not efficiently eliminated and accumulate in lactococcal cultures, and that RecA is needed to deal with the damage they incur. Unexpectedly, thermal stress arrested growth of the recA strain. Immunological data indicate that the recA mutant is deficient in heat-shock proteins DnaK, GroEL, and GrpE. Poor growth at elevated temperature is therefore due to a diminished heat-shock response in the recA strain. In contrast, levels of a novel heat-shock protein, HflB, are elevated. In Escherichia coli, HflB downregulates the heat-shock response by promoting degradation of the transcription factor σ32. We propose that recA regulates the heat-shock response via HflB. This work provides the first evidence showing that two major pathways of stress response, induced by heat shock and DNA damage, are interactive.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1365-2958.1995.mmi_17061121.x
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