The sos response is a cell mediated repair system that involves 2 proteins, LexA and RecA proteins. One protein inhibits transcription of the promoter region whilst the other induces breakdown of the inhibitor (for repair purposes). Though sos response is a repair system, it also induces mutation, in a nicer manner, evolution.
E.coli is a studied model for the SOS response, only recently; the article ‘Aeons of distress: an evolutionary perspective on the bacterial SOS response’ looks upon the different types of bacteria carrying different homologues of the SOS response gene; mainly the lexA motif. Such strains of bacteria include the firmicutes Bacullis subtilise, Actinobacterium Mycobacterium tuberculosis, Thermotogae Thermotoga naepolitana and many others.
It was found that each strain of lexA boxes (in gram positive bacteria) had different sequences, it was then suggested that they evolved through a monophyletic group.
This could prove useful as it may help find the bacteria that had the original lexA box and would give us a chance of studying how it came to be and may give us more insight on evolution.
References
Ivan Erill, Susana Campoy, Jordi Barbé Aeons of distress: an evolutionary perspective on the bacterial SOS response FEMS Microbiology Reviews (OnlineEarly Articles).
