Prions are self-propagating clumps of misfolded protein. At least one prion is transmissible to other prion proteins. The result is a disease similar to viral infection, causing transmissible spongiform encephalopathies. This is a group of progressive conditions that affect the brain (encephalopathies) and nervous system of many animals. The most infamous is bovine spongiform encephalopathy (BSE), the so-called ‘mad cow disease.’ BSE is a fatal neurodegenerative disease that has affected some herds of cows; the disease may be most easily transmitted to humans by eating food contaminated with the brain, spinal cord or digestive tract of infected carcasses.
The new association between bacteria and prions has originated from some new experiments. Microbiologists identified a protein with prion-forming potential in the bacterium Clostridium botulinum. Although the phenomenon remains with one organism, the researchers suggest that other bacteria can also carry proteins with prion-forming potential.
The detection in the bacterium came about after the researcher examined over 60,000 bacterial genomes. The protein identified in Clostridium botulinum is called Rho. In a troubling sign of potential infectivity, when the Rho prions were inserted into yeast cells they began to multiply. The researchers call this the introduction of “heritable changes in the structure and function.”
Importantly, because the protein that has the potential to become a prion regulates gene activity within the bacterial cell, the alteration to the prion state could alter genetic expression and thus bacterial behavior. This may come about as a bacterium adapts to environmental stresses. Such stresses could include the immune system in a mammal and therefore the switch to the prion state could enhance the organism’s ability to cause disease and to evade the immune system surveillance. Such a strategy could also help a bacterium become more resistant to antimicrobials.
The research also raises understanding about prions, indicating they are some form of ancient biological development arising at a time when some bacterial cells began the long and complex process of forming plant and animal cells, dating back to over two billion years ago.
The new research has been published in the journal Science. The research paper is titled “A bacterial global regulator forms a prion.”
