RESUMO
Penicillins are widespread in nature and lethal to growing bacteria. Because of the severe threat posed by these antibiotics, bacteria have evolved a wide variety of strategies for combating them. Here, we describe one unusual strategy that involves the activity of a catalytic carbohydrate. We show that the cyclic oligosaccharide, beta-cyclodextrin (betaCD), can hydrolyze, and thereby inactivate, penicillin in vivo. Moreover, we demonstrate that this catalytic activity contributes to the antibiotic resistance of a bacterium that synthesizes this oligosaccharide in the laboratory. Taken together, these data not only expand our understanding of the biochemistry of penicillin resistance, but also provide the first demonstration of natural carbohydrate-mediated catalysis in a living system.
Assuntos
Ampicilina/farmacologia , Antibacterianos/farmacologia , Bacillus subtilis/efeitos dos fármacos , Escherichia coli/efeitos dos fármacos , Resistência às Penicilinas , beta-Ciclodextrinas/metabolismo , Ampicilina/metabolismo , Antibacterianos/metabolismo , Bacillus subtilis/crescimento & desenvolvimento , Bacillus subtilis/metabolismo , Catálise , Escherichia coli/crescimento & desenvolvimento , Escherichia coli/metabolismo , Hidrólise , Testes de Sensibilidade Microbiana , Amido/metabolismo , beta-Lactamases/metabolismoRESUMO
The bacterium Agrobacterium tumefaciens transforms eukaryotic hosts by transferring DNA to the recipient cell where it is integrated and expressed. Bacterial factors involved in this interkingdom gene transfer have been described, but less is known about host-cell factors. Using the yeast Saccharomyces cerevisiae as a model host, we devised a genetic screen to identify yeast mutants with altered transformation sensitivities. Twenty-four adenine auxotrophs were identified that exhibited supersensitivity to A. tumefaciens-mediated transformation when deprived of adenine. We extended these results to plants by showing that purine synthesis inhibitors cause supersensitivity to A. tumefaciens transformation in three plant species. The magnitude of this effect is large and does not depend on prior genetic manipulations of host cells. These data indicate the utility of yeast as a model for the transformation process and identify purine biosynthesis as a key determinant of transformation efficiency. These findings should increase the utility of A. tumefaciens in genetic engineering.