Antibiotic-resistant bacteria are becoming increasingly difficult to defeat. Some viruses called bacteriophages are able to eat all kinds of bacteria. These microscopic living beings existed before our presence on Earth. This is why some University of California researchersin San Diego, came up with the idea of studying some of these bacteriophage viruses closely in order to find a effective treatment for difficult infections.
In particular, they examined le virus 201phi2-1a giant phage that infects the bacterium Pseudomonas chlororaphis. So called because of its large genome, the jumbo phage uses a particularly effective system to counter the defense mechanisms of bacteria.
Previous research has shown the presence of a protective shield around its genetic material, which makes it particularly formidable.
A protective membrane around viral DNA
Viruses inject their genetic material into the bacterium’s cytoplasm while it takes over organelles in order to replicate. Normally, the entry of viral DNA inside the bacterium activates its CRISPR “immune system”. It is a defense technique that allows the latter to cut foreign DNA at a specific location to make it non-coding.
The molecular biologist Thomas Laughlin and his colleagues discovered that giant phages are able to build a kind protective membrane around their genetic material shortly after entering the host. Thus, bacteria are unable to deactivate their genetic material.
A new method to fight difficult bacteria
Laughlin and his team used cryo-electron microscopy and tomography to study the process of bacterial infection by bacteriophage viruses. They were then able to examine this new nuclear envelope at the atomic scale. This is how they were able to determine that this protective envelope is made up of only one type of protein which they named “chimallin”in reference to the name of an ancient Aztec shield.
Computer modeling then concluded that the phage core selectively allows molecules to pass through tiny pores as would any other cell nucleus. Researchers hope to develop a similar system to end bacterial resistance problems.
SOURCE : SCIENCEALERT