Binding of Ferric Iron to the Cell Walls and Membranes of Bifidobacterium thermophilum:  Effect of Free Radicals

Abstract

Bifidobacterium thermophilum (ATCC 25866) was incubated with 100-120 microM (59)FeSO(4) and 300 microM excess of H(2)O(2) for up to 120 min in the presence and absence of glucose. Samples were withdrawn after 5, 30, 60, and 120 min. These were protoplasted and (59)Fe(III) measured in the supernatant fraction (cell walls) and protoplasts (cell membranes). These experiments were also repeated in the presence of 400 microM Al(III), which, in whole cells, caused an increase in Fe(III) binding. The amount of iron in the cell wall fraction was constant regardless of time of incubation, was unaffected by Al(III), and was reduced by approximately 20% by glucose. On the other hand, the amount of iron on the protoplasts increased with time and was affected by both Al(III) (upward) and glucose (downward). Scatchard plots indicated that the number of Fe(III) binding sites on the cell walls was 37.6 nmol/mg of dry cell weight at zero time, whereas that of cell membranes was (1)/(10) of that. It was concluded that Fe(III) binding by bifidobacterial cell walls was instantaneous and marginally dependent on free radical action. That of the cell membranes was time-dependent and was due to lipid peroxidation initiated by free radicals. Bifidobacteria can therefore function in the intestinal tract as probiotics by making Fe(OH)(3) unavailable to pathogens and by moderating free radical activity in the intestinal tract.

Low iron availability in continuousin vitrocolonic fermentations induces strong dysbiosis of the child gut microbial consortium and a decrease in main metabolites

“…Enterobacteriaceae are very good Fe scavengers (Andrews et al ., ), and lactobacilli do not require Fe for growth in nucleotide‐rich environments (Imbert & Blondeau, ; Elli et al ., ), which gives both bacterial groups a growth advantage during Fe‐restricted conditions. Bifidobacteria are reported to bind Fe to their cell walls and membranes, which may increase their survival during low Fe environmental conditions (Kot & Bezkorovainy, ). The clear growth advantage of bifidobacteria in a complex gut microbiota during very low Fe conditions is demonstrated by their high abundance (64.8%) during the 2,2′‐dipyridyl and Chelex ® fermentation period.…”

“…Enterobacteriaceae are very good Fe scavengers (Andrews et al, 2003), and lactobacilli do not require Fe for growth in nucleotide-rich environments (Imbert & Blondeau, 1998;Elli et al, 2000), which gives both bacterial groups a growth advantage during Fe-restricted conditions. Bifidobacteria are reported to bind Fe to their cell walls and membranes, which may increase their survival during low Fe environmental conditions (Kot & Bezkorovainy, 1999 The findings of this in vitro fermentation studies are very consistent with the data of a recent rat study using an Fe depletion-repletion assay to investigate the impact of Fe on gut microbiota (Dostal et al, 2012). Similar to our in vitro results, Fe deficiency in rats induced a strong decrease in butyrate and propionate production along with a decrease in butyrate-and propionate-producing bacteria.…”

Comparison of the sensitivity of commercial strains and infant isolates of bifidobacteria to antibiotics and bacteriocins

“…They observed that this inhibitory effect could be largely eliminated by pretreating the organism with 100-400 mm aluminum (III). Al (III) is known to potentiate free radical effects in the plasma membrane (Kot & Bezkorovainy, 1999), leading to increased iron binding by B. thermophilum which may potentiate its probiotic action.…”

Identification of iron-regulated genes of Bifidobacterium breve UCC2003 as a basis for controlled gene expression

“…Indeed, it has been hypothesized that one of the beneficial actions of health-promoting or probiotic bacteria is to sequester iron, thus making it less available to pathogens, thus representing another form of nutritional immunity. 17 A further benefit of iron sequestration is that it would abate free radical production in the gastrointestinal tract (GIT) or at sites of inflammation, where OH-free radicals are produced by the action of neutrophils or other means. 18 Iron-induced free radical damage to DNA appears to promote the development of cancer, while cancer cells are also known to grow rapidly in response to iron.…”