An article published in the journal “Nature” reports a study concerning bacterial immune defenses of the CRISPR-Cas type, which could turn out to be a disadvantage against some types of viruses. A team of researchers analyzed the immune systems present in the genome of over 170,000 bacteria to try to understand the reactions against bacteriophage viruses. The conclusion that CRISPR antiviral systems are sometimes a disadvantage offers an explanation of why only a minority of bacteria have them in their DNA. It also offers new information on bacteria’s defense strategies viruses’ attack strategies with a sort of arms race between them.
In recent years we got used to reading research on CRISPR (clustered regularly interspaced short palindromic repeats) systems in connection to genetic manipulation techniques but these are DNA segments that are part of various species of bacteria’s immune system and produce different enzymes useful against bacteriophage viruses. That’s because bacteria and viruses not only attack multicellular organisms, but in some cases they too can be enemies since the so-called bacteriophages attack bacteria.
To try to better understand the mechanisms of this sort of war between bacteria and viruses, a team of researchers conducted some experiments and performed a computer analysis the genomes of 170,000 bacteria, including pathogenic species, to evaluate the link between their immune reactions and the presence of CRISPR-type immune systems.
Among the experiments, a strain of bacteria of the species Pseudomonas aeruginosa with a CRISPR-Cas type immune system was used. It’s a bacterium that’s pathogenic for various species of plants and animals, including humans, also known for its resistance to antibiotics. A strain of this bacterium was infected with some strains of bacteriophage viruses of the order Caudovirales. The bacterium revealed different levels of resistance showing a vulnerability to certain strains of bacteriophages.
A bioinformatic analysis, meaning applying information technology tools to biological research, showed how CRISPR systems are present irregularly among bacteria. It’s possible that bacteria belonging to very different groups evolved acquiring or losing the genes that regulate a CRISPR system independently. The researchers mentioned a kind of arms race between bacteria and viruses with different adaptations that could depend on various factors that change over time, starting with the environment in which they live.
This research offers new information on the immune systems of many pathogenic microorganisms and their possible vulnerabilities. Understanding how certain bacteriophage viruses manage to attack antibiotic-resistant bacteria can be a key to developing new treatments against them.
