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Retrons and Novel Defense Systems Show Activity Against Bacteriophages

Martinez, David (2023) MOBN03 20222
Degree Projects in Molecular Biology
Popular Abstract
Retrons and Novel Defense Systems Show Activity Against Bacteriophages

Bacteria employ a wide array of defense systems against viruses(phages). These defense systems are diverse and novel systems are constantly being uncovered. Retrons are one such example of recently discovered defense systems; although they were discovered in the 1980s, they have only recently been found to play a role in phage defense. Apart from retrons, this study also focuses on several novel gene systems that have been predicted to function in phage defense through their association with other genes involved in bacterial immunity.
Retron Systems
Retrons are bacterial gene elements that are composed of a non-coding RNA (ncRNA), a reverse transcriptase, and... (More)
Retrons and Novel Defense Systems Show Activity Against Bacteriophages

Bacteria employ a wide array of defense systems against viruses(phages). These defense systems are diverse and novel systems are constantly being uncovered. Retrons are one such example of recently discovered defense systems; although they were discovered in the 1980s, they have only recently been found to play a role in phage defense. Apart from retrons, this study also focuses on several novel gene systems that have been predicted to function in phage defense through their association with other genes involved in bacterial immunity.
Retron Systems
Retrons are bacterial gene elements that are composed of a non-coding RNA (ncRNA), a reverse transcriptase, and usually one to two effector proteins. Recent work has shown that retrons function as anti-viral immune systems within bacteria. In this study, a set of seven previously uncharacterized retrons were tested against a diverse array of phages in order to determine whether they also function as defense systems. By observing the appearance of plaques caused by phage infections on lawns of bacteria, it is possible to quantify the defense conferred by a defense system through comparison with plaques on a control lawn. This procedure was performed for all the tested systems using the entire array of phages available. Of the seven retrons tested, four were found to be defensive against one or more phages.

The mechanism through which the retrons conferred defense was then tested by creating growth curves. The growth curves were made by measuring a bacterial culture’s optical density every two minutes. The appearance of a growth curve can provide insights into the defense mechanism. Through the growth curves we could determine that the retrons functioned through abortive infection (abi), a defense strategy that causes cell death/growth arrest once a viral infection is detected.
WYL-associated Systems
Through a bioinformatic analysis, three gene systems were found that were predicted to be involved in viral defense based on their proximity to proteins containing WYL-domains. These WYL-domains have been shown to be associated with other defense systems and it has been hypothesized that WYL may be a regulator of defense systems. These novel systems are not retrons and constitute new types of defense systems that have not been discovered previously. The novel systems were tested in the same fashion as the retrons and two out of the three were found to be defensive. These novel systems were also found to function through abi.

The results confirmed that several of the tested retrons and novel systems function as defense systems against phages. It was also discovered that the functional systems functioned through an abi mechanism. These results are important for understanding defense systems and provide a foundation for further research into these retrons and novel systems. More detailed knowledge about defense systems will also be crucial for the future development of phage therapies and biological tools.

Master’s Degree Project in Molecular Biology, Microbiology 60 credits 2023
Department of Biology, Lund University
Supervisor: Søren Johannes Sørensen Co-Supervisor: Rafael Pinilla Redondo
Section of Microbiology, Department of Biology, University of Copenhagen (Less)
Please use this url to cite or link to this publication:
author
Martinez, David
supervisor
organization
course
MOBN03 20222
year
type
H2 - Master's Degree (Two Years)
subject
language
English
id
9122696
date added to LUP
2023-06-09 15:32:17
date last changed
2023-06-09 15:32:17
@misc{9122696,
  author       = {{Martinez, David}},
  language     = {{eng}},
  note         = {{Student Paper}},
  title        = {{Retrons and Novel Defense Systems Show Activity Against Bacteriophages}},
  year         = {{2023}},
}