Sending Out An SOS.

Antibiotic resistance is occurring at an alarming rate in today’s medical world. For a long time scientists have been puzzled. The question of “Why mutations are happening so fast?” has been raised again and again- now they have finally found the answer. Bacteria make sure that these beneficial mutations take place, thus insuring evolution occurs.

The SOS response in bacteria has long been thought of a last ditch, random and uncontrolled response to environmental stress (e.g. antibiotic), but this is not the case at all! There are in fact key proteins and genes that oversee the “SOS response”.

LexA cleavage and RecA-ssDNA conformational activation work in conjunction with each other to control of the response of SOS.

The paper written by Courcelle, Justin et. al., reveals that bacterial evolution and SOS are not just ruled by the documented 26 genes, it is actually more than 40! This discovery was established when E. coli (wild type and mutant strains) were treated with UV radiation and the resulting gene expression levels were measured via micro arrays. The most amazing thing was that LexA suppressed genes were also found to have different levels and timing of expression after environmental stress was applied.

Interested in how all of this mutation control is coupled to the greater bacterial genomic variation? and how this new proposition of ‘evolution’ is affecting Darwin’s theory?

Just click on the link below!

http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=11333217

References:

1. Cirz, R. T., Chin, J. K., Andes, D. R., de Crecy-Lagard, V., Craig, W. A., Romesberg, F. E. (2005). Inhibition of Mutation and Combating the Evolution of Antibiotic Resistance. PLoS Biology, 3, 1024-1033
2. Courcelle, J., Khodursky A., Peter, B., Brown, P. O., Hanawalt, C. P. (2001). Comparative Gene Expression Profiles Following UV Exposure in Wild-Type and SOS-Deficient Escherichia Coli. Genetics, 158, 41-64

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