Hanne Jensen in the middle, with two of her supervisors, senior scientist Lars Axelssson in Nofima and Stine Grimmer (former Nofima, now Axellus).

How do lactic acid bacteria function?

Lactic acid bacteria (LAB) are a natural part of our intestinal flora, and have received a great deal of attention in recent decades due to the possibility that they have beneficial effects on our health.

PhD student Hanne Jensen at the food research institute Nofima has investigated the interplay between these bacteria and human cells. Such studies may provide insight into how and why they have beneficial effects on health.

Previously unknown beneficial proteins

It has been assumed that two of the mechanisms behind the beneficial effects of LABs are their ability to bind to cells and mucus in the intestine, and their effects on the immune system. Hanne Jensen has investigated several LAB with the aid of methods that are normally used to select probiotic bacteria.

Hanne Jensen is particularly interested in LAB that belong to the Lactobacillus genus, and has mostly investigated these.

“We have shown that strains of the LAB Lactobacillus reuteri differ from other LAB strains, and that they have, among other things, a particularly strong adhesion to intestinal cells. We used mutants of Lactobacillus reuteri to discover a previously unknown surface protein that is important for the ability of the bacteria to attach to intestinal cells and mucus,” says Jensen.

The scientists named this protein “cell and mucus-binding protein A (CmbA)”. They also found a second surface protein in Lactobacillus reuteri, which appears to be significant in the stimulation of cells of the immune system.

“These two findings are pieces of the puzzle that will eventually help us to understand the interplay between LAB and human cells,” concludes Lars Axelsson at Nofima.

melkesyrebakterie

Electron microscopy image of Lactobacillus reuteri bacteria on the surface of intestinal epithelial cells in a model system. Photo: Hanne Jensen/Nofima

Hanne Jensen’s doctoral degree

Hanne Jensen defended her doctoral thesis on 5 December at the Department of Chemistry, Biotechnology and Food Science at the Norwegian University of Life Sciences. Principal supervisor was Tor Lea, and additional supervisors were Senior Scientist Lars Axelsson from Nofima and Stine Grimmer (previously employed as a researcher at Nofima).

The thesis: “In vitro characterization of commercial and potential probiotic lactic acid bacteria: Interactions with human cells.”

Hanne Jensen studied toxicology at the University of Oslo and graduated in 2007. The doctoral work has been funded by the Foundation for Research Levy on Agricultural Products (FFL).

Food safety and quality  

Related content