Antibiotics such as tetracycline, streptomycin, and bacitracin aresmall organic molecules that are synthesized by particular speciesof bacteria. Microbiologists have hypothesized that the reason whycertain bacteria make antibiotics is to kill other species that occupythe same environment. Bacteria that produce an antibiotic may beable to kill competing species. This provides more resources forthe antibiotic-producing bacteria. In addition, bacteria that havethe genes necessary for antibiotic biosynthesis contain genes thatconfer resistance to the same antibiotic. For example, tetracyclineis made by the soil bacterium Streptomyces aureofaciens. Besidesthe genes that are needed to make tetracycline, S. aureofaciensalso has genes that confer tetracycline resistance; otherwise, itwould kill itself when it makes tetracycline. In recent years, however,many other species of bacteria that do not synthesize tetracyclinehave acquired the genes that confer tetracycline resistance.For example, certain strains of E. coli carry tetracycline-resistancegenes, even though E. coli does not synthesize tetracycline. Whenthese genes were analyzed at the molecular level, it was found thatthey are evolutionarily related to the genes in S. aureofaciens. Thisobservation indicates that the genes from S. aureofaciens havebeen transferred to E. coli.How could the widespread use of antibiotics to treat diseaseshave contributed to the proliferation of many bacterial speciesthat are resistant to antibiotics?
Antibiotics such as tetracycline, streptomycin, and bacitracin are
small organic molecules that are synthesized by particular species
of bacteria. Microbiologists have hypothesized that the reason why
certain bacteria make antibiotics is to kill other species that occupy
the same environment. Bacteria that produce an antibiotic may be
able to kill competing species. This provides more
the antibiotic-producing bacteria. In addition, bacteria that have
the genes necessary for antibiotic biosynthesis contain genes that
confer resistance to the same antibiotic. For example, tetracycline
is made by the soil bacterium Streptomyces aureofaciens. Besides
the genes that are needed to make tetracycline, S. aureofaciens
also has genes that confer tetracycline resistance; otherwise, it
would kill itself when it makes tetracycline. In recent years, however,
many other species of bacteria that do not synthesize tetracycline
have acquired the genes that confer tetracycline resistance.
For example, certain strains of E. coli carry tetracycline-resistance
genes, even though E. coli does not synthesize tetracycline. When
these genes were analyzed at the molecular level, it was found that
they are evolutionarily related to the genes in S. aureofaciens. This
observation indicates that the genes from S. aureofaciens have
been transferred to E. coli.
How could the widespread use of antibiotics to treat diseases
have contributed to the proliferation of many bacterial species
that are resistant to antibiotics?
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