Tiny viruses that attack bacteria, known as phages, are responsible for the rapid evolution of bacterial defense systems and the emergence of so-called superbugs, according to a new study.
Because bacteria grow so quickly, evolutionary adaptations like resistance to antimicrobial drugs can reveal themselves in just a matter of days.
Until now, microbiologists assumed evolutionary adaptions emerged from a homogenous clonal population of bacteria via random mutations. However, the latest findings — published Friday in the journal Science Advances — showed bacterial parasites, or phages, provide certain bacteria with an evolutionary advantage.
“Essentially, a parasite became a weapon,” senior author Vaughn Cooper, professor of microbiology and molecular genetics at the University of Pittsburgh, said in a press release. “Phages endowed the victors with the means of winning. What killed off more sensitive bugs gave the advantage to others.”
To properly treat bacterial infections, study authors suggest medical researchers and doctors must better understand the evolutionary trajectory of the problem bacteria.
Currently, clinicians attempting to diagnose and treat bacterial infections are like late-arriving theatergoers walking in mid-scene, watching the action unfold without the necessary context.
According to the latest analysis, bacteria and invading phages undergo an initial period of rapid co-evolution, a complex and chaotic series of genetic alterations.
When scientists sequenced six bacteria strains found in an infected pig wound, they found phages rapidly jumping from host to host. Even phages that conferred no evolutionary benefit were found incorporated in the genomes of the bacteria strains. Clones of the most successful bacteria strains featured three or four different phages.
“It showed us just how much phages interact with one another and with new hosts,” Cooper said. “Characterizing diversity in early bacterial infections can allow us to reconstruct history and retrace complex paths of evolution to a clinical advantage. And, with growing interest in using phages to treat highly resistant infections, we are learning how to harness their potency for good.”