Are bacteria really evolving?
Back in 1988, explorers frozen in 1845 were autopsied at the
Now researchers have gone a step further. They have isolated bacterial DNA from Ice Age permafrost and found genes coding for resistance to several classes of antibiotics, including β-lactams, tetracycline, and glycopeptide antibiotics.
Then, focusing on the genes encoding vancomycin resistance, they recreated those gene products in the lab. The three enzymes thus produced worked together to resist vancomycin in the same way as their modern counterparts. They conclude, “Antibiotic resistance is a natural phenomenon that predates the modern selective pressure of clinical antibiotic use.”
So how did the bacteria already have suitable weapons years before their enemy was invented? Antibiotics and their antidotes are actually natural substances produced by fungi, algae, and bacteria. Dr. Gerry Wright explains, “Antibiotics are part of the natural ecology of the planet so when we think that we have developed some drug that won't be susceptible to resistance or some new thing to use in medicine, we are completely kidding ourselves. . . . Microorganisms have figured out a way of how to get around them well before we even figured out how to use them.” He adds, “Antibiotics are remarkable resources that need to be carefully husbanded.”
Some of this genetic material is in a form that can be transferred to other microorganisms. Microbiologist Dr. Stuart Levy, who has warned of profligate use of antibiotics for 30 years, explains, “What had been missed in the 1960s and 1970s was the ease with which resistance could appear,” he said. “Bacteria share these genes like baseball cards with each other.”
So is antibiotic resistance the poster-child of evolution? No. There was a time when people thought bacteria evolve resistance because they “need” to. But—as demonstrated in this study and in the 1988 one—the variations and mutations that confer resistance are already in the genomes of some bacteria. The “resistance information” does not necessarily develop in response to the antibiotic threat. Natural selection allows resistant bacteria to survive and reproduce, replenishing the bacterial population. And those surviving bacteria are still bacteria—the same kind of bacteria they were all along.