Artificially constructed viruses literally tore apart deadly bacteria
Researchers from Northwestern University changed the DNA sequence of bacteriophages and introduced it into Pseudomonas aeruginosa (P. aeruginosa). These bacteria can cause deadly infections and are often resistant to antibiotics. Once inside a bacterial cell, the artificially constructed viral DNA successfully bypasses the defense mechanisms, integrates into the chromosome and launches a conveyor belt for the production of new viral particles. They destroy the cell – literally explode it from the inside.
This scientific work was the next step towards the creation of so-called designer viruses that can be used as drugs against antibiotic-resistant bacteria. In parallel, such studies help to better understand the biology of phages.
The study results were published at the end of January 2024 in the journal Microbiology Spectrum.
Study leader Erica Hartmann notes:
Sustainability [бактерий] to antimicrobials is sometimes called a “silent pandemic.” The number of infections and deaths from them is rising around the world. This is a huge problem. Phage therapy is an underappreciated alternative to antimicrobials. But in many ways, phages are the “final frontier” of microbiology. We don't know much about them. The more we learn about how phages work, the more likely we are to develop effective treatments. Our project is cutting-edge in the sense that we are studying the biology of phages in real time as they are developed.
An alternative to antibiotics is vital
In the modern world, the problem of antibiotic resistance is growing: bacteria are becoming more and more resistant to drugs. This makes it increasingly difficult to treat many infections. For example, the US Centers for Disease Control and Prevention (CDC) reports that about 3 million infections caused by resistant microorganisms are detected annually in America, and they claim more than 35 thousand lives.
The problem is compounded by the fact that the development of new antibiotics has long stalled. This forces scientists to look for alternative treatments. In recent years, interest in drugs based on bacteriophages has been growing.
Phages perform quite well in the fight against dangerous pathogens, but not everything is so simple with them. Firstly, these viruses are very selective: each bacteriophage can infect only one type of bacteria or, in general, only certain strains within a species. Secondly, bacteria can also develop resistance to phages. Thirdly, phages are not just medicinal molecules, but complex biological objects. Their action is not always easy to accurately predict.
In general, despite the fact that phages are the most numerous creatures on our planet (there are about 10 of them31), there are still a lot of gaps in knowledge about them.
Erica Hartmann says:
For every bacterium there are a dozen corresponding phages. Thus, there are an astronomical number of phages on Earth, but we have studied only a few of them. We didn't have the motivation to study them all seriously. Now such motivation has appeared, and we are increasing the number of tools with which we can study them.
Treatment without side effects
Usually, when phages are needed to fight a particular infection, scientists search for suitable viruses in the environment and use them as is or modify them in a certain way. Bacteriophages destroy a certain type of bacteria, but do not affect others, do not disrupt the microflora and do not infect human cells.
In the future, it would be possible to create a large bank of phages in which viruses against various pathogens would be stored, and constantly replenish it. Having identified certain pathogens in a patient, the doctor could request the necessary bacteriophages from the bank, and the hospital pharmacy would prepare an individual medicine from them. Drugs that do this are called mainline drugs.
Scientists from Northwestern University decided to see if they could construct phages that would effectively destroy Pseudomonas aeruginosa (P. aeruginosa). This is a very dangerous bacteria, especially for people with weakened immune systems. P. aeruginosa often causes nosocomial infections and is multidrug resistant.
An artificial virus bypassed the defense and destroyed the victim
The process of creating genetically engineered phages was divided into two stages. To create synthetic DNA, we used regular baker's yeast – Saccharomyces cerevisiae. The fact is that, unlike bacteria, viral genes are practically not expressed in fungal cells and do not affect the properties of microorganisms. That is, there is infection with the phage, but it does not lead to any “symptoms” or consequences. This allows extensive and varied modifications to viral DNA to be carried out safely.
But yeast is not bacteria, and full-fledged viral particles will not be synthesized in them. Therefore, the next step was to “reboot” the new bacteriophage. For this purpose, electroporation was used: on bacterial cells P. aeruginosa They applied high-voltage electrical pulses, made small holes in them and injected viral genetic material. In fact, the same thing happened as during natural infection. The viral DNA integrated into the bacterial chromosome and the production of bacteriophages began.
Some bacteria were able to recognize and destroy viral DNA. Then scientists optimized the process and disabled the protective antiviral mechanisms.
After this, the already tested method was tried on two phages, which in the wild are not capable of infecting P. aeruginosa. And again everything worked out.
The remarkable difference between phages and other drugs is that they reproduce themselves. When an infected bacterium dies, many new viruses come out, and they also go in search of victims.
Overall, the technology looks very promising. The authors of this study plan to continue the work. So far only with phages that infect P. aeruginosa, but gradually they will probably reach others.
