Bacterial cells transmit memories to offspring

Bacterial cells can 'remember' brief, temporary changes to their bodies and immediate surroundings, a new study has found. And, although these changes are not encoded in the cell's genetics, the cell still passes memories of them to its offspring -- for multiple generations.

 

Although these changes are not encoded in the cell's genetics, the cell still passes memories of them to its offspring -- for multiple generations.

 

Not only does this discovery challenge long-held assumptions of how the simplest organisms transmit and inherit physical traits, it also could be leveraged for new medical applications.

 

For example, researchers could circumvent antibiotic resistance by subtly tweaking a pathogenic bacterium to render its offspring more sensitive to treatment for generations.

 

A central assumption in bacterial biology is that heritable physical characteristics are determined primarily by DNA. But, from the perspective of complex systems, we know that information also can be stored at the level of the network of regulatory relationships among genes.

 

The researchers wanted to explore whether there are characteristics transmitted from parents to offspring that are not encoded in DNA, but rather in the regulatory network itself.

 

It was found that temporary changes to gene regulation imprint lasting changes within the network that are passed on to the offspring. In other words, the echoes of changes affecting their parents persist in the regulatory network while the DNA remains unchanged.

 

Since researchers first identified the molecular underpinnings of genetic code in the 1950s, they have assumed traits are primarily -- if not exclusively -- transmitted through DNA. However, after the completion of the Human Genome Project in 2001, researchers have revisited this assumption.

 

The objective of the study is to one day see if it is [possible to isolate the causes for the simplest single-cell organisms, since researchers can control their environment and interrogate their genetics. If they canwe observe something in this case, it shouldbe possible to attribute the origin of non-genetic inheritance to a limited number of possibilities -- in particular, changes in gene regulation.

 

The regulatory network is analogous to a communication network that genes use to influence each other. The research team hypothesized that this network alone could hold the key to transmitting traits to offspring.

 

The research team used a mathematical model of the regulatory network to simulate the temporary deactivation (and subsequent reactivation) of individual genes in Escherichia coli.

 

They discovered these transient perturbations can generate lasting changes, which are projected to be inherited for multiple generations. The team currently is working to validate their simulations in laboratory experiments using a variation of CRISPR that deactivates genes temporarily rather than permanently.

 

If the changes are encoded in the regulatory network rather than the DNA, the research team questioned how a cell can transmit them across generations. The researchers propose that the reversible perturbation sparks an irreversible chain reaction within the regulatory network.

 

As one gene deactivates, it affects the gene next to it in the network. By the time the first gene is reactivated, the cascade is already in full swing because the genes can form self-sustaining circuits that become impervious to outside influences once activated.

 

The study also suggests that other organisms have the necessary elements to exhibit non-genetic heritability. "In biology, it's dangerous to assume anything is universal.

 

See: Yi Zhao, Thomas P. Wytock, Kimberly A. Reynolds, Adilson E. Motter. Irreversibility in bacterial regulatory networks. Science Advances, 2024; 10 (35) DOI: 10.1126/sciadv.ado3232

 

Posted by Dr. Tim Sandle, Pharmaceutical Microbiology Resources (http://www.pharmamicroresources.com/)