ETH Zurich biologists, led by professors Martin Ackermann and Wolf-Dietrich Hardt, in collaboration with Michael Doebeli of the University of British Colombia in Vancouver (CN), have been able to describe how random molecular processes during cell division allow some cells to engage in a self-destructive act to generate a greater common good, thereby improving the situation of the surviving siblings.
The biologists investigated this unusual biological concept using the pathogenic salmonella bacteria as an example. Diseases caused by salmonellae are very unpleasant and even life-threatening. When contaminated food is consumed – for example, egg-based foods or chicken and meat – salmonella bacteria enter the gastrointestinal tract where it triggers infection. Vomiting and diarrhea can last for days.
Normally, salmonellae grow poorly in the intestine because they are not competitive with other bacteria of the gut. However, this dynamic changes if salmonellae induce an inflammatory response, namely diarrhea, which suppresses the other bacteria. The inflammation is triggered by salmonellae penetrating into the intestinal tissues. Once inside, salmonellae is killed by the immune system. This in turn creates a conflict: salmonellae are either suppressed by the other bacteria in the gut, or die while trying to eliminate these competitors.
As Ackermann, Hardt and Doebeli report, salmonellae have found a surprising solution to this conflict. Inside the gut, the salmonella bacteria forms two groups that engage in job-sharing. A first group invades the tissue, triggers an inflammation, then dies. A second group waits inside the gut until the inactivation of the normal intestinal flora gives them an opportunity to strike. This second group then multiplies unhindered.
What determines whether an individual salmonella bacterium cell self-sacrifices, or whether it will wait and benefit from the sacrifice of others? The two groups are clones of the same genotype, so genetic differences do not play a role. Rather, the difference between the two groups is a result of random molecular processes during cell division. Cellular components are randomly distributed between the two daughter cells with each cell receiving a different amount. The resulting imbalance can be amplified and lead to different properties of the clonal siblings.
In recent years it has been recognized that such random processes in a cell can have a large influence on individual cells. The work by the ETH Zurich researchers reveals a new biological explanation for this phenomenon. The two salmonella phenotypes share their work, with the result being that they achieve what a single phenotype on its own would not be capable of doing. This scenario is fundamentally different from the usual explanations and presupposes that individual phenotypes interact and have an effect on one another. The self-sacrifice of phenotypes may be quite common among pathogenic bacteria, for example, among the pathogens causing diarrhea after antibiotic treatment (clostridia) or pneumonia (streptococci).
Ackermann observes, "Random processes could promote job-sharing in many different types of organisms. Many bacteria manufacture substances which are toxic to their hosts but which are only released into the host environment if the bacteria sacrifice themselves — if this is the sole method to get the toxin out of the cell. This is why every cell makes a decision: toxin and death or no toxin.”
Reference: Ackermann M, et al. Self-destructive cooperation mediated by phenotypic noise; Nature 454, 987-990 (21 August 2008), doi: 10.1038/nature07067
Stay prepared and protected with Infection Control Today's newsletter, delivering essential updates, best practices, and expert insights for infection preventionists.
Breaking the Cycle of Silence: Why Sharps Injuries Go Unreported and What Can Be Done
Published: July 24th 2025 | Updated: July 23rd 2025Despite decades of progress in health care safety, a quiet but dangerous culture still lingers: many health care workers remain afraid to report sharps injuries, fearing blame more than the wound itself.
US Withdrawal From UNESCO Signals a Dangerous Step Back for Global Science
July 22nd 2025In a decision heavy with consequence and light on foresight, the US has once again chosen to walk away from UNESCO, leaving behind not just a seat at the table, but a legacy of global scientific leadership that now lies in question.
Pathogen Pulse: Facilities Need the SPD, Yersinia Enterocolitica Outbreak, and More
July 22nd 2025From unsterilized surgical tools in Colorado to a years-long methicillin-resistant Staphylococcus aureus (MRSA) outbreak in Virginia and a surging measles crisis in Canada, recent headlines reveal the fragile front lines of infection prevention and the high stakes when systems fail.
Telemedicine's Transformative Role in PPE Distribution and Sterile Equipment Management
July 22nd 2025In an era defined by digital transformation and post-pandemic urgency, telemedicine has evolved beyond virtual visits to become a vital infrastructure for delivering personal protective equipment (PPE) and managing sterile supplies. By enabling real-time forecasting, remote quality control, and equitable distribution, telemedicine is revolutionizing how health care systems protect both patients and providers.
Reducing Hidden Risks: Why Sharps Injuries Still Go Unreported
July 18th 2025Despite being a well-known occupational hazard, sharps injuries continue to occur in health care facilities and are often underreported, underestimated, and inadequately addressed. A recent interview with sharps safety advocate Amanda Heitman, BSN, RN, CNOR, a perioperative educational consultant, reveals why change is overdue and what new tools and guidance can help.