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Identification of novel phage resistance mechanisms in Campylobacter jejuni NCTC 12662

Geslain, Sandra Amandine Marie (2021) MOBN03 20202
Degree Projects in Molecular Biology
Popular Abstract
Bacteria-eating viruses and their prey: an eternal war

The antibiotic resistance problem: what if bacterial viruses were the solution?

Nowadays, we hear more and more dreadful stories about nasty bacteria becoming resistant to our best antibiotics. Researchers are therefore spending much time trying to think of alternatives, one of which could be the use of bacteriophages -literally meaning bacteria eaters -. Bacteriophages, or phages for short, are viruses that only infect and kill bacteria, thus posing no risk to animals or humans. Phages are naturally present everywhere, from oceans to soil, and are thus constantly menacing bacteria in their environment. This means that bacteria need to have an arsenal of defence systems in order... (More)
Bacteria-eating viruses and their prey: an eternal war

The antibiotic resistance problem: what if bacterial viruses were the solution?

Nowadays, we hear more and more dreadful stories about nasty bacteria becoming resistant to our best antibiotics. Researchers are therefore spending much time trying to think of alternatives, one of which could be the use of bacteriophages -literally meaning bacteria eaters -. Bacteriophages, or phages for short, are viruses that only infect and kill bacteria, thus posing no risk to animals or humans. Phages are naturally present everywhere, from oceans to soil, and are thus constantly menacing bacteria in their environment. This means that bacteria need to have an arsenal of defence systems in order to survive phage attacks. Similarly, phages must develop new weapons to keep prospering, or they would cease to exist. There is much interest in understanding the mechanics of this seemingly eternal war between bacteria and phages, especially as phages are a promising way to control bacterial infections.

Is it possible for seemingly sensitive bacteria to survive exposure to several phages at the same time?

Since phages are numerous and varied in nature, we wanted to investigate how sensitive bacteria might survive exposure to phages utilising different offensive strategies. The bacterium chosen for this study was Campylobacter jejuni, which is one of the biggest causes of food poisoning. More specifically, one type that is sensitive to phages was chosen and exposed to three different phages in different combinations. Surprisingly, many surviving bacteria could be recovered in all cases, which means that resistance might arise faster than expected. It was, later on, found that many bacteria acquired resistance to one or even several of the phages they were exposed to! These results highlight the rapidity with which some species of bacteria can adapt to survive their predators.

How do these bacteria manage to survive phage attacks?

We were very curious to understand in what way these bacteria changed in order to survive phage attacks. Therefore, we decided to analyse their genetic code (DNA) using sequencing-based methods to see whether some changes occurred. Interestingly, several genes were identified that appeared linked to the acquisition of resistance to the phages. To verify whether these genes were required to sustain or prevent phage attacks, mutant bacteria were created using molecular biology methods.
These mutant bacteria lacked two genes, and the loss of either of these genes caused them to become completely resistant to one of the phages used in the study. These results show that these two genes are required for the phage infection to succeed. Remarkably, these two genes seem to be involved in the production of the bacterial capsule, a sugar coat that surrounds the bacteria. It is likely that changes in the structure of the coat (caused by deletion of the genes) allow the bacteria to go under the radar and escape recognition by the phage.

This study has shed light on the interactions that occur between bacteria and phages. Understanding how bacteria become phage-resistant is critical for making phage cocktail -a mix of many phages- that can prevent or treat bacterial infections.



Master’s Degree Project in Molecular Biology, 60 credits, 2021.
Department of Biology, Lund University

Supervisor: Martine Camilla Holst Sørensen
University of Copenhagen, Department of Veterinary and Animal Sciences, PhageBio group (Less)
Please use this url to cite or link to this publication:
author
Geslain, Sandra Amandine Marie
supervisor
organization
course
MOBN03 20202
year
type
H2 - Master's Degree (Two Years)
subject
language
English
id
9058164
date added to LUP
2021-06-23 11:22:46
date last changed
2021-06-23 11:22:46
@misc{9058164,
  author       = {{Geslain, Sandra Amandine Marie}},
  language     = {{eng}},
  note         = {{Student Paper}},
  title        = {{Identification of novel phage resistance mechanisms in Campylobacter jejuni NCTC 12662}},
  year         = {{2021}},
}