Phenotypic characterization of a soxR null Streptomyces coelicolor mutant

Posted May 12th, 2010 at 3:27 pm.

Sahitya Penumetcha

Mentor: Dr. Monica Chander

SoxR is a transcription factor that senses reactive oxygen species via redox-active iron sulfur clusters, and mobilizes an oxidative stress response in Escherichia coli. Studies in Streptomyces coelicolor (a model antibiotic-producing bacterium) indicate that SoxR does not play an analogous role in this organism. A S. coelicolor soxR null mutant is not hyper-sensitive to redox-cycling drugs. Instead, this mutant hyper-produces the pigmented antibiotics undecylprodigiosin and actinorhodin compared to the wild type strain. This suggests that SoxR may regulate antibiotic metabolizing genes in S. coelicolor. Two identified SoxR targets in S. coelicolor, SCO2478 ad SCO4266, encode putative products with homology to antibiotic tailoring enzymes. The expression of these two genes is significantly down-regulated in a soxR mutant, and also in a mutant that does not produce pigmented antibiotics. Based on these observations, we hypothesize that SoxR senses the presence of endogenous antibiotics and stimulates the expression of enzymes that modify these antibiotics in order to protect the bacterium from self-toxicity. To test this hypothesis we will extract and quantify the amount of pigmented antibiotics produced by soxR mutant and wild type strains. These antibiotics will be further analyzed by thin layer chromatography and nuclear magnetic resonance spectroscopy, which will reveal if the compounds produced by the wild type and soxR mutant strains are similar or distinct.

Filed under: 2009,Chander, Dr. Monica,Penumetcha, Sahitya by Ann Dixon

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