Mutation That Increases Listeria Survival Identified

A single-point mutation newly identified in the genome of Listeria monocytogenes increases the pathogen’s ability to withstand temperature-related and osmotic stress, researchers in Ireland reported. The same group also described a previously unidentified twisting of L. monocytogenes cells into a corkscrew shape in response to increased stresses.

The survival-increasing mutation, designated betL*, represents a “double-edged sword,” the lead researcher suggested.

“From a food safety perspective, a mutation with the potential to induce such dramatic shifts in cell growth and survival under stress—making an already dangerous pathogen even more formidable—raises significant food-safety concerns that need to be addressed. However, from a synthetic biology point of view, a boosted-stress resistance locus such as betL* represents a useful biobrick for the design and construction of more physiologically robust pharmabiotic strains,” said Roy D. Sleator, PhD, a lecturer in the department of biological sciences at Cork Institute of Technology.

The reason that the L. monocytogenes cells twist into a spiral shape under stress is so far not understood, but Dr. Sleator suggested it might be an effort by the organism to reduce exposure to the stressor. He is senior author of a paper describing the mutation and the corkscrew stress response in Bioengineered.

“In essence, we now have a piece of DNA which we know can significantly boost the stress resistance of less hardy probiotic strains such as Lactobacillus or Bifidobacterium, allowing greater survival in yogurt formulations stored in the cold. Indeed, work currently under way in my lab is focused on testing this hypothesis,” Dr. Sleator said in an email to Food Quality.

A food science expert, Kathryn J. Boor, PhD, professor of food science and dean of the College of Agriculture and Life Sciences at Cornell University in Ithaca, N.Y., suggested that this work might also have implications for fighting dangerous organisms (Dr. Boor was not involved in the research).

“Further investigation of the specific mechanism(s) underpinning these physiological phenomena are likely to lead to more effective strategies for destroying potentially dangerous microbes or for prolonging the lives of highly desirable microbes (e.g., probiotics) under food-like storage conditions,” she said via email.