Antibiotics have saved countless lives for decades. Yet the pathogens they kill, antibiotics are an ancient enemy, one they already specializes in fighting.
It turns out that the spread of antibiotic resistance may not be as constrained as we assumed, giving more species easier access to antibiotic resistance than previous models would have us believe.
The findings come from a study conducted by bioinformatics researcher Jan Zrymac from Chalmers University of Technology in Sweden, which looks for signs of dynamics between elements of DNA called plasmids.
If a genome were a cookbook, the plasmid could be imagined as a loose scrap of paper of prized dishes stolen from friends and relatives. Many have instructions for making materials that can help bacteria survive under stressful conditions.
And for bacteria, a single dose of antibiotics is almost as stressful as it gets.
While we have been using them as medicine for the better part of a hundred years, the truth is that we have just taken inspiration from a microbial arms race that can be almost as old as life itself.
As different species of microbes gave birth to new methods to speed the growth of their bacterial competitors through age, bacteria have come up with new methods to overcome them.
These defense measures are often conserved in the coding of a plasmid, allowing bacterial cells to easily share resistance through a process called conjugation. If the term evokes thoughts of encounters during prison visits, then you need to extend your imagination a bit … between single-celled organisms.
For plasmids that are widely distributed among cells in an act of bacterial hanky-panky, they need to possess a region of genetic coding called the root–Of–Transfer sequence, or oriT.
This sequence is enclosed with an enzyme that unlocks the plasmid for easy replication, and then re-seals it. Without the ority, a plasmid’s secret recipe is sure to remain in its owner’s possession.
In the past, it was believed that each plasmid required both an ORT and a code for an enzyme to share in the acts of conjugation.
Today, it is clear that the enzyme is not required for a particular oriT sequence, meaning that if a bacterial cell contains multiple plasmids, some may benefit from an enzyme encoded by another.
If we want to come up with a list of plasmids that can be shared – including instructions for antibiotic resistance – we just need to know how many contain the ority sequence.
Unfortunately, finding and quantifying these sequences is a time-intensive and laborious task. So Zrimec has developed far more efficient means for discovering oriT based on the unique characteristics of the physical properties of coding.
They applied their findings to a database of over 4,600 plasmids, calculating how common mobile plasmids were based on the spread of ORT.
It turns out that we were probably off the mark as to how common this essential sequence is, with the Gymnich results eight times higher than previous estimates.
Considering other infection factors, this may mean that there are many mobile plasmids among bacteria, with twice as many bacterial species in their possession than we imagined. and that’s not all.
There was another discovery made Zrimec which is a cause for concern.
“Plasmids belong to different motility groups, or MOB groups, so they can’t just transfer between any bacterial species,” Zrymek says.
Yet his research suggests that in one of the half oriT sequences he found conjugate enzymes fit from a different MOB group, suggesting the boundaries between bacterial species might be more permeable to plasmids than we think.
All this is disturbing news in light of the race to develop new antibacterial treatments.
“These results may mean that there is a strong network for transferring plasmids between bacteria in humans, animals, plants, soil, aquatic environments and industries,” says Zrimec.
“Resistance genes occur naturally in many different bacteria in these ecosystems, and hypothetical networks may mean that genes in all of these environments can be transferred to bacteria that cause disease in humans Huh.”
This is an arms race in which we put ourselves to save lives – never imagining how efficient bacteria matching our firepower would be.
Such technology will help us to understand better what we are doing. And already, it doesn’t look pretty.
This research was published in Microbiology open.