Breaking the biofilm shield that harbours foodborne pathogens

Biofilms have become a major environmental microbiology concern in the food industry over the last 30 years, due to their potential for contamination of food. They can also damage food processing equipment because their slimy structure adheres to surfaces like stainless steel, plastic and rubber that are commonly used in food processing facilities.

Biofilms are structured communities of bacteria encased in a protective slime matrix — called extracellular polymeric substances (EPS) — which can act as hidden reservoirs for foodborne pathogens as they are resistant to standard cleaning agents.

Scientists from the Department of Microbiology at the University of Malaga have now discovered an unknown mechanism that allows the bacterium Bacillus cereus to protect itself against antibiotics and adverse conditions.

The study, published in the journal Science Advances, reveals how these bacteria form biofilms that act as a protective shield. These discoveries have potential for opening up opportunities to weaken these biofilms and improve their control in both the medicine and food industry.

Breaking the shield

The research has identified the molecular system that enables the assembly of the so-called protective ‘scaffold’. Specifically, the scientists have described a mechanism based on three key proteins —TasA, CalY and CapP— that coordinate the formation of filamentous structures on the exterior of the bacteria. This system, they point out, works in a highly controlled way, making sure the bacterial community is built in an organised and efficient manner.

One of the most important pieces of evidence is the role of the CapP protein, which acts as an ‘orchestra conductor’, controlling when and how these structures are assembled. “Without this control, the bacteria would not be able to form biofilms properly, which demonstrates their essential role in the survival of the microorganism,” the researchers said.

In addition, the study reveals that Bacillus cereus has a remarkable capacity for adaptation. If this system fails, the bacterium activates alternative mechanisms — such as extracellular DNA production or changes in mobility — to maintain their protection. This ‘plasticity’ helps explain why biofilms are so difficult to eradicate.

The full study can be read here.

Image credit: University of Malaga