Bacteria Share Antibiotic Resistance
Antibiotic resistance does not “evolve” in a Darwinian way. Rather, a new study shows that bacteria share their genetic information.
Researchers at Sandia National Labs decided to decode the genome of Klebsiella pneumoniae, a bacterium containing enzymes that frustrate medical teams because of “their ability to survive any antibiotics you throw at them.” The article is about “Tracing the evolution of a drug-resistant pathogen,” but there’s very little mention of evolution below the headline. What is dubbed evolution (in the only other use of the word) is really information sharing:
To better understand how the process works, they focused on the large mobile DNAs, such as plasmids, which exist as free DNA circles apart from the bacterial chromosome, and genomic islands, which can splice themselves into the chromosome. These mobile DNAs are major mechanisms for evolution in organisms that lack a true nucleus. Genomic islands and plasmids carry genes that contribute to everything from metabolism to pathogenicity, and move whole clusters of genes all at once between species.
The researchers found that “in some cases, bacteria can receive a new set of genes all at once and in the process become pathogenic.” But did those genes evolve by a Darwinian process? There is no mention of mutation or natural selection in the article. Instead, a subheading reads, “Bacteria share genetic material with other bacteria.” They do this by conjugation or by ferrying the genes through viruses. “The great challenge is that bacteria can easily share their defenses,” a Sandia researcher says. There was a passing reference to new genes, without elaboration:
Over the two decades that various bacterial genomes have been sequenced, researchers have found rampant gene sharing. “They are not so much generating new genes all the time — that does happen slowly — but what they mainly do is shuffle genes around,” Williams said. “The new gene combinations can quickly give bacteria a new pathogenic niche. They may then invade more tissues or survive in even more conditions.”
As a result, the “bug is always armed” with the genetic information it needs to evade antibiotics. Nothing further was said about how bacteria “evolve” resistance to our drugs.
So much for another leading example of evolution in action. If the information is already present, it’s not evolution; it’s technology sharing.