RESEARCHERS with the Institute of Food Research (IFR) have characterized the coat of a potential poultry probiotic, thus providing the first clues of how it may be used to exclude pathogenic bacteria from chickens.
Lactobacillus johnsonii has previously been shown to exclude Clostridium perfringens from the gut of poultry, opening the door to it being developed as a way of reducing necrotic enteritis in poultry and food poisoning in humans.
Recently, researchers at IFR, which is strategically supported by the U.K. Biotechnology & Biological Sciences Research Council, found that the bacteria make coats for themselves that play important roles in colonization in this strain.
In research that was published in The Journal of Biological Chemistry, the researchers presented the first characterization of what makes up this coat. This will help them determine the role the coat plays and help in the development of these bacteria as a way of combatting C. perfringens.
Using nuclear magnetic resonance spectroscopy, the researchers discovered that the coat is made up of two types of exopolysaccharides (EPS), which are long sugar-containing molecules that many bacteria use to encapsulate themselves. This capsule may help the bacteria cope with environmental stress or aid in colonization and adhesion.
Different bacterial strains have different EPS structures, and understanding this is important as the structures represent a key way bacteria interact with the world around them.
"Characterizing the EPS structures in the L. johnsonii strain is the first step to explaining how it might outcompete C. perfringens," said Dr. Arjan Narbad.
Previous studies had identified potential genes in L. johnsonii for producing EPS, giving the researchers tools to probe how the bacteria synthesize these molecules. Knocking out the whole cluster of EPS genes meant the bacteria produced no capsule.
Further analysis of the genes by IFR doctoral student Enes Dertli uncovered their potential roles in the capsule biosynthesis process, but more research is needed to fully understand the system and also how it is regulated.
The structures of these two EPS molecules appear to be unique to this strain.
Structural features, such as the phosphorylation patterns, are likely to be a major influence on how well bacteria adhere. Other structural modifications such as acetylation are thought to help protect EPS from the enzymes produced by gut bacteria.
This strain of L. johnsonii is now being taken through farm-scale trials to assess its potential use to combat pathogenic infections of poultry by bacteria such as C. perfringens. This study provides insights into exactly how this works, and future work will focus on elucidating how the EPS molecules in the coat contribute to colonization and pathogen exclusion.