Spotlight on Chemists

Jennifer Lillig: Bacteriocins and Listeriosis

L. Monocytogenes

Foodborne Listeriosis and L. Monocytogenes

The threat of bacterial pathogens has come to light due to advancing global research on pathogens, in light of the COVID pandemic. This has led to increased awareness of food safety. Among these pathogens is Listeria Monocytogenes, a species of bacteria responsible for listeriosis that Dr. Jennifer Lillig investigates, a rare but severe disease that infects humans through the ingestion of contaminated food products such as milk, dairy, and fish [1]. Of all foodborne diseases, listeriosis is one of the most severe due to its high mortality rate of 20%–30% [3].

It is also suggested that L. monocytogenes can be contracted by humans and animals via many possible routes. In the worst cases, invasive listeriosis is known to affect high-risk groups – such as pregnant women, the elderly, and people with weakened immune systems. The disease’s clinical manifestations include fever and nausea, meningitis, perinatal infections, and miscarriages [2]. One of the non-pathogenic bacteria proven to be effective in killing Listeria is the strain found in lactic acid. It produces peptides (short chains of amino acids) called ‘bacteriocins’. These target L. Monocytogenes through a complex chemical mechanism, essentially sticking to the surface of the Listeria and “poking a hole” in its membrane [4]. In trying to understand the key features of these molecules and their interactions, Jennifer Lillig is working towards their development as safe and potent drugs.  

Bacteriocins: How do they function?

Bacteriocins are proteins or peptides made by the ribosomes*, which can combine with the receptors on the surface of the sensitive bacteria in order to kill it. Characterized by a strange similarity of chemical structure, bacteriocin molecules work through the division of responsibilities: one half of the molecule identifies the target bacteria while the other kills it. However, a most interesting finding by Dr. Jennifer Lillig and her team concludes that these halves can also kill the bacteria independently of each other once divided [4]. Additionally, the chemical stability of these molecules and their ability to be broken down within the digestive tract provides an ideal opportunity for their usage. They may be used not only for treatment but also for the prevention of listeriosis. 

*Ribosomes are the sites of protein synthesis in the cell.

Learn More

If you’d like to hear more about the wondrous bacteriocin molecule and ongoing research into using LAB (Lactic acid bacteria) for disease prevention, visit us on Spotify to listen to our ChemTalk podcast. Dr. Jennifer Lillig, professor and biochemist at Sonoma State University, discusses what makes bacteriocin perfect for a targeted attack, how she aims for a comprehensive and thorough curriculum for her students, and what got her interested in the field of biochemistry. 

Find the ChemTalk podcast here: https://open.spotify.com/episode/2OfSHor6ANsXUge2oWtUvy

Works Cited

[1]  Magalhães, R., Mena, C., Ferreira, V., Silva, J., Almeida, G., Gibbs, P., & Teixeira, P. (2014). Bacteria: Listeria monocytogenes. Encyclopedia of Food Safety, 450-461. https://doi.org/10.1016/B978-0-12-378612-8.00101-3

[2] Allerberger, F., & Wagner, M. (2010). Listeriosis: a resurgent foodborne infection. Clinical Microbiology and Infection, 16(1), 16-23. https://doi.org/10.1111/j.1469-0691.2009.03109.x

[3] “The Prevalence of Listeriosis”  World Health Organisation, 20 February 2018

[4] Lillig, Jennifer. Personal Interview. Conducted by Roxanne Salkeld. 19 August 2022.