Characterization of mutator phenotypes in Proteus mirabilis isolates

Abstract

Strains that present high mutation rates (mutators) were detected in several bacterial genera. In those, the increase in mutation rates is related to defects in the DNA repair systems. Since 1885, bacteria from the genus Proteus, were described as gram-negative and gelatinase secreting, but during experiments conducted in the late twentieth century, some strains of Proteus mirabilis showed a high rate of emergence of colonies without the ability to secrete gelatinase, an irreversible and disadvantageous phenotype for the progress of the infection. Similar observations were made for the auxotrophic phenotype, in which 54% of the studied colonies, that were initially prototrophic, generated auxotrophic mutants at frequencies higher than 10-3. This phenotype was also irreversible and the same phenomenon of genetic instability was induced in Escherichia coli when it was transformed with a resistance plasmid of P. mirabilis. The observations were not explained by the researchers that described them, and considering the high rate of healthcare-associated infections caused by P. mirabilis, it is important to verify the occurrence of mutator strains in clinical isolates of the species, as it was done for E. coli and Salmonella typhimurium. We want to observe the prevalence of this phenomenon and identify the molecular mechanisms leading to the mutator phenotype in P. mirabilis.