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The Spx/YjbH system in Bacillus subtilis

Matavacas Martínez, Judith (2018) MOBN03 20172
Degree Projects in Molecular Biology
Popular Abstract
Spx or why bacteria don’t suffer from burnout

Bacteria also suffer from stress. In general, any fluctuation in the environment of bacteria can cause stress on them. For instance, too hot or too cold temperature, or changes in the pH. In order to survive, they need mechanisms to cope with it. Most of these mechanisms involve proteins, which can be seen as tools that respond to stress.

In the bacterium Bacillus subtilis, the Spx protein has a key role in fighting against a situation called oxidative stress, but also other types of stress such as changes in temperature. Spx is always produced in the cell. However, Spx would be a burden for the bacterium when the conditions are good. Imagine carrying a backpack full of tools when you... (More)
Spx or why bacteria don’t suffer from burnout

Bacteria also suffer from stress. In general, any fluctuation in the environment of bacteria can cause stress on them. For instance, too hot or too cold temperature, or changes in the pH. In order to survive, they need mechanisms to cope with it. Most of these mechanisms involve proteins, which can be seen as tools that respond to stress.

In the bacterium Bacillus subtilis, the Spx protein has a key role in fighting against a situation called oxidative stress, but also other types of stress such as changes in temperature. Spx is always produced in the cell. However, Spx would be a burden for the bacterium when the conditions are good. Imagine carrying a backpack full of tools when you don’t need to fix anything. It would be a waste of energy. YjbH protein, another important player in this mechanism, has the solution to that: it brings Spx to a sort of “shredder”, which destroys it. What happens when the bacterium encounters stress? YjbH proteins in the bacterium sense the adverse conditions and stick together, forming aggregates. This aggregation of YjbH can be understood as a system to turn off the destruction of Spx. If YjbH is forming aggregates, it can’t find Spx and destroy it, so Spx is free to perform.

In this thesis, the Spx/YjbH system in B. subtilis was studied. More specifically, one of the main aims was to further study the mechanism by which YjbH senses the stress and forms aggregates, which is not yet well understood. To study it, we used fluorescence microscopy. YjbH was joined to a fluorescent protein, and this fusion was introduced in the bacterium. This allowed localization of YjbH in the cell.

It was found that YjbH can also sense and aggregate under other types of stress (Figure). The presence of certain antibiotics (vancomycin and kanamycin) induced aggregation. This suggested that Spx might also be needed to cope with these adverse conditions. Furthermore, one part of YjbH seemed to sense the stress (and aggregate) without other parts of the protein. When this part was compared to the corresponding one from a bacterium that grows in high temperatures, the later was found to be less sensitive to the stress, since less aggregation was seen.

Now, you might be wondering what the value of understanding the Spx/YjbH mechanism is. Because this mechanism has a really important function helping the bacterium to survive, the two proteins could be used as targets for new antibiotics. Although B. subtilis is not harmful for humans, the system is also found in Staphylococcus aureus and Listeria monocytogenes, which are human pathogens.

Master’s Degree Project in Molecular Biology 60 credits 2018
Department of Biology, Lund University

Supervisor: Claes von Wachenfeldt
Department of Biology, Lund University (Less)
Please use this url to cite or link to this publication:
author
Matavacas Martínez, Judith
supervisor
organization
course
MOBN03 20172
year
type
H2 - Master's Degree (Two Years)
subject
language
English
id
8947057
date added to LUP
2018-06-08 15:45:03
date last changed
2018-06-08 15:45:03
@misc{8947057,
  author       = {Matavacas Martínez, Judith},
  language     = {eng},
  note         = {Student Paper},
  title        = {The Spx/YjbH system in Bacillus subtilis},
  year         = {2018},
}