Characterization of Staphylococcus aureus clpX and yjbH mutants selected in vivo
(2021) MOBN03 20202Degree Projects in Molecular Biology
- Abstract
- Methicillin-resistant Staphylococcus aureus (MRSA) colonises up to 30% of the population and is responsible for diseases ranging from mild skin infections to endocarditis, some of which result in death. This is due to the resistance of MRSA to several commonly used as well as last line antibiotics, complicating treatment further. This study examines clinical MRSA isolates with inactivating mutations in clpX and yjbH. ClpX is a highly conserved ATP-dependent chaperone which can associate with ClpP to form the ClpXP protease. In S. aureus, the adaptor protein YjbH is known to bind proteins and target them for degradation by ClpXP. Spx, a global transcriptional regulator, is an example of such a protein and has been shown to accumulate in the... (More)
- Methicillin-resistant Staphylococcus aureus (MRSA) colonises up to 30% of the population and is responsible for diseases ranging from mild skin infections to endocarditis, some of which result in death. This is due to the resistance of MRSA to several commonly used as well as last line antibiotics, complicating treatment further. This study examines clinical MRSA isolates with inactivating mutations in clpX and yjbH. ClpX is a highly conserved ATP-dependent chaperone which can associate with ClpP to form the ClpXP protease. In S. aureus, the adaptor protein YjbH is known to bind proteins and target them for degradation by ClpXP. Spx, a global transcriptional regulator, is an example of such a protein and has been shown to accumulate in the absence of clpX and yjbH, correlating with an increase in resistance. Spx is essential for the viability of cells and is regulated by the redox status of cells, activating or repressing genes in response to disulfide stress. Inactivation of Spx renders the cells hypersensitive to a range of stress conditions, including antibiotic exposure, therefore, it is not unlikely that constitutive expression of the Spx regulon could contribute to survival during antibiotic stress. The aim of this study was to elucidate why mutations in clpX and yjbH are selected for in S. aureus clinical isolates. The most probable hypothesis is that the mutations allow for Spx accumulation which in turn, directly or indirectly through a gene under Spx control, causes antibiotic resistance. This hypothesis was tested by studying the relationship between clpX, yjbH and spx, by constructing a Spx-YjbH double mutant, as well as performing antibiotic resistance tests. The results of this study, in accordance with previous findings, indicate that the YjbH, ClpX and Spx pathway may play a role in causing antibiotic resistance. (Less)
- Popular Abstract
- How do bacteria become resistant to last-line antibiotics?
Methicillin-resistant Staphylococcus aureus (MRSA) causes severe bacterial infections which are often resistant to several commonly used antibiotics. Unfortunately, MRSA infections that are resistant to last-line antibiotics have also started to appear. This is an issue since it means that there are no antibiotics left that are strong enough to treat such infections. This increased resistance is likely due to mutations forming in the bacteria as a result of being exposed to antibiotics, pressuring the bacteria to mutate to be able to survive in the presence of antibiotics. Therefore, a mutation seen in MRSA cells isolated from a patient treated with last-line antibiotics, will... (More) - How do bacteria become resistant to last-line antibiotics?
Methicillin-resistant Staphylococcus aureus (MRSA) causes severe bacterial infections which are often resistant to several commonly used antibiotics. Unfortunately, MRSA infections that are resistant to last-line antibiotics have also started to appear. This is an issue since it means that there are no antibiotics left that are strong enough to treat such infections. This increased resistance is likely due to mutations forming in the bacteria as a result of being exposed to antibiotics, pressuring the bacteria to mutate to be able to survive in the presence of antibiotics. Therefore, a mutation seen in MRSA cells isolated from a patient treated with last-line antibiotics, will be discussed in this summary.
The mutation occurs in an enzyme called ClpXP, which roams around bacterial cells looking for proteins that are no longer needed to chop up into smaller proteins, acting as a waste disposer. Hence, ClpXP is needed to ensure that the daily lives of bacteria run smoothly. Researchers have found that, if we remove or mutate ClpXP in bacteria, they grow well in the presence of antibiotics, meaning that they become resistant. It is believed that this is because proteins that would otherwise be chopped up by ClpXP, will continue to exist and build up in the cells. If these proteins are involved in activating systems to fight against the action of antibiotics, that is when resistance is encountered. For example, if ClpXP is mutated, then a protein called Spx is allowed to build-up.
Spx controls the production of many important proteins that bacteria need to survive. Such proteins are involved in activating systems to defend themselves against stressful situations and harmful substances. If bacteria lose these proteins, they will not survive, meaning that removing Spx from cells makes them very sick and vulnerable. Researchers have shown that if Spx is removed from bacteria that are very resistant to antibiotics, such as MRSA, they are no longer resistant and grow very poorly. This suggests that Spx, or one of the proteins that it controls the production of, is likely involved in causing resistance. It has been speculated that, since Spx is involved in activating mechanisms to deal with other stressful situations, it is probably well equipped to deal with the stress of antibiotic exposure. Therefore, Spx is a very good candidate to further investigate and by figuring out the role that it plays in causing antibiotic resistance, we might be able to figure out how MRSA develops resistance.
Master’s Degree Project in Molecular Biology (Microbiology) 60 credits 2021
Department of Biology, Lund University
Advisor: Associate Professor Dorte Frees
Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen. (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/9060870
- author
- Justh De Neczpal, Annie
- supervisor
- organization
- course
- MOBN03 20202
- year
- 2021
- type
- H2 - Master's Degree (Two Years)
- subject
- language
- English
- id
- 9060870
- date added to LUP
- 2021-07-05 11:27:17
- date last changed
- 2021-07-05 11:27:17
@misc{9060870,
abstract = {{Methicillin-resistant Staphylococcus aureus (MRSA) colonises up to 30% of the population and is responsible for diseases ranging from mild skin infections to endocarditis, some of which result in death. This is due to the resistance of MRSA to several commonly used as well as last line antibiotics, complicating treatment further. This study examines clinical MRSA isolates with inactivating mutations in clpX and yjbH. ClpX is a highly conserved ATP-dependent chaperone which can associate with ClpP to form the ClpXP protease. In S. aureus, the adaptor protein YjbH is known to bind proteins and target them for degradation by ClpXP. Spx, a global transcriptional regulator, is an example of such a protein and has been shown to accumulate in the absence of clpX and yjbH, correlating with an increase in resistance. Spx is essential for the viability of cells and is regulated by the redox status of cells, activating or repressing genes in response to disulfide stress. Inactivation of Spx renders the cells hypersensitive to a range of stress conditions, including antibiotic exposure, therefore, it is not unlikely that constitutive expression of the Spx regulon could contribute to survival during antibiotic stress. The aim of this study was to elucidate why mutations in clpX and yjbH are selected for in S. aureus clinical isolates. The most probable hypothesis is that the mutations allow for Spx accumulation which in turn, directly or indirectly through a gene under Spx control, causes antibiotic resistance. This hypothesis was tested by studying the relationship between clpX, yjbH and spx, by constructing a Spx-YjbH double mutant, as well as performing antibiotic resistance tests. The results of this study, in accordance with previous findings, indicate that the YjbH, ClpX and Spx pathway may play a role in causing antibiotic resistance.}},
author = {{Justh De Neczpal, Annie}},
language = {{eng}},
note = {{Student Paper}},
title = {{Characterization of Staphylococcus aureus clpX and yjbH mutants selected in vivo}},
year = {{2021}},
}