Biologist investigates how gene-swapping bacteria evade antibiotics
“One of the prevailing theories for why bacteria make these antibiotic compounds is to fight off competition. But the bacteria that make the antibiotics have to be resistant to those antibiotics. Therefore, many encode antibiotic resistance genes against their own products.”
Random genetic mutation is one way bacteria become antibiotic resistant, but another way is by exchanging antibiotic resistance genes with one another in close quarters, such as in human wounds or on hospital surfaces.
In a recent study, published in June in the Journal of Bacteriology, Palmer and her colleagues shed light on a gene-swapping process called conjugation, which, she tells her students, is like bacterial sex.
“These bacteria utilize an enzyme to chemically scan genetic material within each cell, and at a specific sequence of bases, or ‘letters,’ in the DNA, they add a chemical component called a methyl group, essentially ‘tagging’ that material,” Palmer said. “The methyl group becomes a signal for ‘me’.”
Another enzyme patrols the bacterial cell, and when it finds an untagged DNA sequence that doesn’t belong, the enzyme destroys it. More.
This sounds like a mechanism for horizontal gene transfer, not like sex, as among animal life forms. The methyl tagging part is interesting. Readers?
Memory lane: Remember when natural selection pure and simple was thought to account for antibiotic resistance?:
How exactly does antibiotic resistance evolve? How have such small and simple organisms managed to repeatedly outpace our drugs? The process is quite simply evolution by natural selection — but bacteria have a few secret weapons that give them an edge. Imagine a population of bacteria infecting a patient in a hospital. The patient is treated with an antibiotic. The drug kills most of the bacteria but there are a few individual bacteria that happen to carry a gene that allows them to survive the onslaught of antibiotic. These survivors reproduce, passing on the gene for resistance to their offspring, and soon the patient is populated by an antibiotic resistant infection — one that not only affects the original patient but that can also be passed on to other patients in the hospital.
See also: Horizontal gene transfer: Sorry, Darwin, it’s not your evolution any more
Follow UD News at Twitter!