Antibiotic resistance to pathogenic bacteria in humans has spread farther than expected, as it has been discovered that bacteria can swap DNA far more readily than thought possible.
A growing threat, antibiotic resistance has emerged faster than thought possible. Some 33 000 deaths have occurred to antibiotic resistant infections in Europe alone, and finding new antibiotics or even alternatives are a top research priority. Totally different strains of bacteria can swap genetic information through the use of containers called plasmids. Plasmids are small containers of DNA which are kept outside of their chromosomes. When two bacteria come into contact, they can copy plasmids to one another in a process called conjugation (also known as “bacterial sex“). This is the most important means by which bacteria spread antibiotic resistance.
“In recent years, we’ve seen that resistance genes spread to human pathogens to a much greater degree than anyone expected,” said Jan Zrimec, a researcher in systems and synthetic biology at the Chalmers University of Technology. “Many of the genes appear to have originated in a wide array of bacterial species and environments, such as soil, water, and plant bacteria.
“This has been difficult to explain because although conjugation is very common, we’ve thought that there was a distinct limitation for which bacterial species can transfer plasmids to each other. Plasmids belong to different mobility groups or MOB groups, so they can’t transfer between just any bacterial species.”
Among his developments, he has written an algorithm that can sift through substantial amounts of plasmid DNA to pick out sections of DNA which are necessary for conjugation (known as oriT regions, where the enzyme relaxase can bind to and snip out DNA). This algorithm can then sort the plasmids into groups based on their oriT regions. His new method differs from the standard one because it analyses oriT regions by their physiochemical properties instead of searching DNA for the enzyme sequence for relaxase, or the point where it can bind to. This method is less time-consuming and resource intensive than the standard one.
Previously, it was thought that a plasmid had to have both the relaxase enzyme and the oriT sequence to bind to, but a bacterial cell can have an oriT region for conjugation to occur. With his new algorithm, he has been able to explore the DNA of 4600 plasmids from different bacteria found in nature.
– There may be eight times as many oriT regions than those discovered with standard methods.
– There may be twice as many mobile plasmids as previously known.
– There also may be twice as many bacterial species with mobile plasmids as previously known.
– More than half the plasmids have an oriT group matching to an enzyme for conjugation from a plasmid that already been classified in a different MOB group. This means that they could be transferred from a different plasmid in the same cell.
The last finding suggests that there may be far greater interchange between bacteria than had been previously been believed.
“This has been a major limitation of the research field up to now,” Zrimec said. “I hope that the methods will be able to benefit large parts of the research into antibiotic resistance, which is an extremely interdisciplinary and fragmented area. The methods can be used for studies aiming to develop more effective limitations to antibiotic use, instructions for how antibiotics are to be used, and new types of substances that can prevent the spread of resistance genes at the molecular level.”
Source: News-Medical.Net
Journal information: Zrimec, J. (2021) Multiple plasmid origin‐of‐transfer regions might aid the spread of antimicrobial resistance to human pathogens. MicrobiologyOpen.doi.org/10.1002/mbo3.1129.
