Complementary discoveries have the potential to improve treatment options for antibiotic resistant infections.
Researchers from the University of Illinois have made complementary discoveries that improve our understanding of bacterial immune systems and offer new strategies to combat antibiotic infections.
Antibiotic -resistant bacteria, often called superbacious, represent a serious threat because they are difficult to treat and can cause higher mortality rates from infections that are generally manageable. These results highlight the critical need for alternatives to traditional antibiotics.
Viruses that kill bacteria, called phages, are powerful antimicrobials that can be used to treat infections. However, bacteria are equipped with a set of immune systems, including CRISPR-CAS, which protect against Phages attacks. These immune systems are problematic because they can reduce the effectiveness of phage therapeutic treatments.
Asma Hatoum-Aslan, associate professor of microbiology, studies the internal functioning of bacterial immune systems by emphasizing the development of effective phages therapies. The research of his laboratory focuses on CRISPR-CAS and other immune systems in staphylococci, bacteria living for the skin that frequently cause antibiotic infections in humans. Two articles recently published by its laboratory describe the discovery of the first anti-crispr protein type III-A and discover a mechanism by which antiviral immune systems can propagate and potentially compromise the efficiency of phage therapy.
Closely with a new protein that inhibits Crispr-Cas immunity
CRISPR-Cas immune systems use a special complex to detect and destroy nucleic acids with phage origins. This complex is made up of small RNAs linked to one or more nucleases associated with CRISPR.
Of the six types of CRISPR-CAS systems, Type III is considered to be the most complex. While most of the CRISPR systems target
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“Data-Gt-translate-attrattes =” ({“attribute =” “tabindex =” 0 “role =” link “> rna The invaders, type III systems target both. Type III systems are also the only CRISPR variety known to use a second messenger signaling mechanism that stimulates case nucleases and gives an additional protective layer by recruiting the help of housewives generally intended for other cellular activities. Consequently, Type III CRISPR-CAS systems are incredibly effective in cleaning phage infections.
Did that aroused the question: have the phages have changed ways to retaliate? To answer this, the members of the Hatoum-Aslan laboratory have detected a large collection of phages for the ability to escape Type III-A CRISPR-CAS systems and have discovered a new anti-crispr protein. Their results, published in Nucleic acid searchHighlight the capacity of the ACRIIIA1 anti-crispr protein to link the complex associated with CRISPR and to block its functions.
“Having access to a diversified collection of Phages was essential for this initial discovery,” said Hatoum-Aslan. “I have developed a phage discovery course that I have been teaching since 2016. Each spring, I have a class full of students looking for phages that infect Staphylococcus bacteria. We therefore produce this large collection of phages that is still developing. »»
After having identified phages with anti-crispr activity, the next challenge of researchers was to determine which specific genes were responsible. After examining a pool of more than 200 genes – a lot with unknown functions – the laboratory has managed to identify Acriiia1The first III-A type anti-crrispr gene, in a Hatoum-Aslan effort invented “Genetics Gymnastics”.
By coupling pairs of related phages which were resistant to the CRISPR system, the members of the laboratory reduced their location of interest, focusing on a short segment of around 2,000 nucleotides. The cloning and testing of several genes in this region allowed Hatoum-Aslan to locate that of anti-crispr activity and its students.
Additional experiences have revealed that Acriiia1 is unique in its composition; It is a small protein that is strongly linked to small RNAs, including fragmented Arnts, which are part of the cell construction machinery of the cell.
“We are not entirely sure of the way in which these RNA fragments help the phage to escape the CRISPR, but we believe that they could indirectly prevent housekeeping nucleases from degrading the genetic material of the phage by inhibition competitive, “said Hatoum-Aslan. “If you throw damaged RNA to these nucleases as a distraction, they will have other things to chew. In the meantime, the phage manages to finish its replication and escape. »»
Hatoum-Aslan hopes that the phages designed with anti-crispring proteins will be more effective in the treatment of antibiotic resistant infections when used in therapeutic applications.
“One of the advantages of teaching the discovery of phages is to raise this collection of phages that we can share with clinicians who use phage therapy to resolve obstinate infections,” said Hatoum-Aslan. “We recently connected with an orthopedic surgeon in Pittsburgh and sent him part of our savage. S. Epidermidis Phages to treat patients with infections in their medical implants. »»
The long-term objective of the laboratory is to design therapeutic phages which can overcome Crispr-Cas and other defenses by equipping them with proteins like Acriiia1.
But while Phage therapy has proven to be promising in certain case studies, it has not yet become a routine treatment in the United States. An outstanding problem concerning researchers is the pure volume of the anti-a-a-a-a-bacteria defenses used by bacteria, and the potential for phage resistance mechanisms to spread quickly. In an additional article, Hatoum-Aslan’s laboratory has dug more deeply in the antiviral arsenal in staphylococci.
Mobilize the defenses: SCCDUDE cassettes as a source of antiviral propagation
Seeking to better understand the whole battery of the antiviral defenses in the staphylococci, Hatoum-Aslan and his team identified all the known defenses and their genomic locations in more than 1,000 strains of S. Aureus And S. Epidermidis. Their analysis revealed a major path by which antiviral defenses can spread.
This analysis, described in
