The bacterial foodborne pathogen Listeria monocytogenes is the causative agent of listeriosis, a debilitating disease linked with about 2,500 illnesses and more than 500 deaths in the U.S.A. each year. A characteristic feature of L. monocytogenes is its ability to grow at cold temperatures and even in the presence of high concentrations of salt - traditional food preservation techniques which arrest the growth of most other pathogens.
The bacterium protects itself from such stresses by twisting into a protective corkscrew type shape in an effort to reduce its exposure to the stress—in the same way a human might wrap up tight—hugging the core to reduce the effects of the cold.
The researchers have identified a single point mutation (out of a total of 3 million or so nucleotides that constitute the entire listerial genome), which dramatically improves the growth of the pathogen in the refrigerator.
The authors say that this mutation represents "a double edged sword;" "from a food safety perspective, a single point mutation with the potential to induce such dramatic shifts in cell growth and survival at low temperatures—making an already dangerous pathogen even more formidable—raises significant food-safety concerns which need to be addressed."
However, from a synthetic biology point of view, such a boosted-stress resistance gene represents a useful BioBrick (or building block) for the design of more physiologically robust probiotics or, indeed, plants that are more resistant to cold arid conditions.
The paper, "A single point mutation in the listerial betL σA-dependent promoter leads to improved osmo- and chill-tolerance and a morphological shift at elevated osmolarity," will be published in the November/December 2013 issue of Bioengineered but is available open access now.