Heat shock protein protects bacteria from plasma treatment

A heat shock protein protects the cells against protein clumping. It degrades, nevertheless, over longer treatment periods.

Plasmas are used, for instance, in wound treatment against pathogens which are immune to antibiotics. Nevertheless, bacteria can defend themselves: They employ a heat shock protein that protects them. A research team headed by Professor Julia Bandow and Dr. Tim Dirks from the Chair for Applied Microbiology at Ruhr University Bochum, Germany, showed that bacteria that overproduce the warmth shock protein Hsp33 can withstand plasma treatment more effectively than others. The researchers also demonstrated which components of the plasma activate the warmth shock protein. The team published their findings within the Journal of the Royal Society Interface on October 25, 2023.

All bacteria inactivated after three minutes

When treated with plasma, proteins unfold, lose their natural functions and might clump together. Their clumping is toxic to cells and might result in their inactivation. The bacterial heat shock protein with a size of 33 kDa (kilo Dalton), known as Hsp33, prevents clumping by binding unfolding proteins.

To seek out out whether an excess of Hsp33 protects cells from plasma, the researchers treated strains that overproduce the protein with the Cinogy plasma source, which is already utilized in dermatology. These strains survived significantly higher than wild-type bacteria after a brief treatment of around one minute. “After a treatment of three minutes, the cells that produce Hsp33 in excess were also inactivated,” Tim Dirks points out.

Species that activate the warmth shock protein

The researchers proved that Hsp33 is activated by plasma by treating the purified heat shock protein with the plasma source. “This activation is related to the oxidation and unfolding of the protein and is definitely reversible,” explains Tim Dirks. “Nevertheless, we also showed that Hsp33 was completely degraded by longer plasma treatment times of 1 hour.” As well as, the protein’s ability to bind a zinc atom was adversely affected by plasma. This zinc atom strengthens the natural three-dimensional structure of the protein in its inactive state.

Since nothing was previously generally known as to which plasma-produced species can activate Hsp33, the researchers created various stressors which are known to be produced by plasma and treated Hsp33 with them one after the other.

This showed that Hsp33 is activated by superoxide, singular oxygen, and atomic oxygen, but doesn’t react to hydroxyl radicals and peroxynitrite.”

Tim Dirks, Chair for Applied Microbiology, Ruhr University Bochum, Germany

This provides a sign of the interaction of those species with the bacterial cells. For instance, superoxide is one in all the primary species generated by oxidative stress within the body, similar to by our immune system in macrophages. A rapid response of Hsp33 to one in all these species generated early on would due to this fact be advantageous for the bacterium for rapid protection against oxidative stress. “Superoxide appears to act as a signaling molecule for bacteria, which signals further oxidative stress,” the research team concludes.