Enhanced Biofilm Formation by Ferrous and Ferric Iron Through Oxidative Stress in Campylobacter jejuni

Abstract

Campylobacter is a leading foodborne pathogen worldwide. Biofilm formation is an important survival mechanism that sustains the viability of Campylobacter under harsh stress conditions. Iron affects biofilm formation in some other bacteria; however, the effect of iron on biofilm formation has not been investigated in Campylobacter. In this study, we discovered that ferrous (Fe2+) and ferric (Fe3+) iron stimulated biofilm formation in Campylobacter jejuni. The sequestration of iron with an iron chelator prevented the iron-mediated biofilm stimulation. The level of total reactive oxygen species (ROS) in biofilms was increased by iron. However, the supplementation with an antioxidant prevented the total ROS level from being increased in biofilms by iron and also inhibited iron-mediated biofilm stimulation in C. jejuni. This suggests that iron promotes biofilm formation through oxidative stress. Based on the results of fluorescence microscopic analysis, Fe2+ and Fe3+ enhanced both microcolony formation and biofilm maturation. The levels of extracellular DNA and polysaccharides in biofilms were increased by iron supplementation. The effect of iron on biofilm formation was also investigated with 70 C. jejuni isolates from raw chicken. Regardless of the inherent levels of biofilm formation, iron stimulated biofilm formation in all tested strains; however, there were strain variations in iron concentrations affecting biofilm formation. The biofilm formation of 92.9% (65 of 70) strains was enhanced by either 40 μM Fe2+ or 20 μM Fe3+ or both (the iron concentrations that enhanced biofilm formation in C. jejuni NCTC 11168), whereas different iron concentrations were required to promote biofilms in the rest of the strains. The findings in this study showed that Fe2+ and Fe3+ contributed to the stimulation of biofilm formation in C. jejuni through oxidative stress.

Iron homeostasis in Mycobacterium tuberculosis is essential for persistence

“…In addition, the increased intracellular Fe level favouring biofilm formation in the mutant strain was not surprising. The role of Fe in biofilm production is well-documented in several bacterial pathogens including Mtb 37 , Pseudomonas aeruginosa 38 , Staphylococcus aureus 39 , and Campylobacter jejuni 40 .…”

Non-Lethal Effects of N-Acetylcysteine on Xylella fastidiosa Strain De Donno Biofilm Formation and Detachment

“…Indeed, the increase in biofilm biomass upon exposure to NAC might have been an adaptive mechanism adopted by the bacteria to protect themselves from the deleterious effect of ROS. According to previous studies, several bacteria respond to sub-lethal doses of ROS by increasing biofilm formation [39,[58][59][60]. The NAC promotion of biofilm formation was previously described by Yin et al [61], where they showed an increasing biofilm formation in Staphylococcus aureus, Enterococcus faecalis, and Pseudomonas aeruginosa caused by the combination of NAC and serum transferrin.…”

Anti-adhesion activity of phytochemicals to prevent Campylobacter jejuni biofilm formation on abiotic surfaces

“…Different microscopy techniques have also been used for direct determination of numbers of cells attached to an abiotic surface or formed into a biofilm (Asakura et al 2007;Wagle et al 2019). The formation of biofilms can also be assessing according to EPS production, using fluorescence microscopy, where the biofilms can be stained as follows (Oh et al 2018):…”