Scientists find out how sticky mucus helps bacteria survive

Bacteria have the ability to adapt to their environment. One such survival strategy involves biofilm formation, which prevents immune system agents or antibiotics from entering bacteria. The scientists found that changes in biofilm structure due to temperature changes are regulated by the production of a new extracellular protein, BsaA, in the bacteria Clostridium perfringens. The research results are published by Biofilms and Microbes journal.

Clostridium perfringens is a species of gram-positive, obligate anaerobic spore-forming bacteria of the genus Clostridia. It is a sanitary indicative organism. Clostridium lives in a variety of environments, soil, and animal intestines and can cause food poisoning, gas gangrene, and antibiotic-associated diarrhea. It is an anaerobic bacteria that cannot grow outside the host. Although it is common knowledge that bacteria can turn into spores in order to evade environmental influences.

It also turned out that Clostridium is capable of forming biofilms. In these biofilms, the bacterial community is covered with a dense matrix of so-called extracellular polymeric substances (EPS). They contain proteins, nucleic acids, and sugar molecules – thus protecting themselves from external hazards. As of today, it is still unclear how Clostridium uses biofilms to survive in oxygen-rich environments that are toxic to them.

The researchers created a library of 1,360 mutant cells in Clostridia to see which proteins are required for biofilm formation at 25°C. During the screening, they discovered the presence of a new protein called BsaA, which is made inside the bacteria and transported outside. Without BsaA, bacteria either formed a fragile biofilm. The researchers then showed that several BsaA proteins assembled in the polymer outside the cells to form a stable mucous biofilm that has adhesion properties. When exposed to the antibiotic penicillin G or oxygen, clostridia lacking the BsaA protein have significantly reduced survival compared to normal bacteria of this species

The research provides insight into the development of new antibacterial strategies, scientists say.