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An article in the UMU Microbial Biotechnology group, led by professor Antonio Sánchez Amat, shows, thanks to the study of isolated phages of sea water, that the two CRISPR-Cas systems of the bacterium Marinomonas mediterranea interact in the resistance against the infection.
The research, published in the prestigious eLife magazine, led by Nobel laureate Randy Schekman, has the collaboration of the University of Standford (California) and the University of Otago (New Zealand).
For this study has been taken as a model to Marinomonas mediterranea, a bacterium that grows on the marine plant Posidonia oceanica and from which different strains have been isolated in coastal waters of Murcia, such as Cabo de Palos, and other areas of the Mediterranean Sea.
From this same environment have been isolated phage, viruses that infect bacteria, specific against M. mediterranea.
The analysis of the genome of the different strains of this bacterium is allowing advance in the study of the role of the CRISPR-Cas systems in the resistance to the isolated phages.
M. mediterranea has two CRISPR-Cas systems, type IF and III-B respectively.
These systems allow the capture of small fragments of the phages that infect the bacteria as 'vaccine' to defend against new infections of the same virus.
The system III-B possesses a novel mechanism of acquisition of that genetic immunity from RNA.
The description of this system in Marinomonas mediterranea was published in the journal Science in 2016.
The most relevant result of the new study published in the journal eLife, is that the two CRISPR systems present in M. mediterranea act as a double barrier of defense of the bacterium against the attacks of the virus.
Thanks to the work of the Microbial Biotechnology group it has been found that the spacers of the IF system are used by this system and also by the system III-B.
"What we have seen is that there are two surveillance systems, if the phages escape from the first, the second manages to stop the infection. In the article it has been shown that in the absence of the system III-B mutants that escape from the IF system appear easily "The cooperation of the two systems allows the bacterium to ensure survival by eliminating phages," explains Sánchez Amat.
These results contribute to understanding why many microorganisms coexist with different types of CRISPR-Cas systems.
Source: Universidad de Murcia
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