Iron supplements are widely consumed; however most of the iron is not absorbed and enters the colon where potentially pathogenic bacteria can utilise it for growth. This study investigated the effect of iron availability on human gut microbial composition and function using an in vitro colonic fermentation model inoculated with faecal microbiota from healthy adult donors, as well as examining the effect of iron on the growth of individual gut bacteria
.
Batch fermenters were seeded with fresh faecal material and supplemented with the iron chelator, bathophenanthroline disulphonic acid (BPDS). Samples were analysed at regular intervals to assess impact on the gut bacterial communities. The growth of
Escherichia coli
and
Salmonella typhimurium
was significantly impaired when cultured independently in iron-deficient media. In contrast, depletion of iron did not affect the growth of the beneficial species,
Lactobacillus rhamnosus
, when cultured independently. Analysis of the microbiome composition
via
16S-based metataxonomics indicated that under conditions of iron chelation, the relative abundance decreased for several taxa, including a 10% decrease in
Escherichia
and a 15% decrease in
Bifidobacterium
. Metabolomics analysis using
1
H-NMR indicated that the production of SCFAs was reduced under iron-limited conditions. These results support previous studies demonstrating the essentiality of iron for microbial growth and metabolism, but, in addition, they indicate that iron chelation changes the gut microbiota profile and influences human gut microbial homeostasis through both compositional and functional changes.
Venesection is the cornerstone of haemochromatosis treatment. Venesection leads to a compensatory increase in intestinal iron absorption. Reduced faecal iron availability leads to shifts in human colonic microbial composition. Changes in the human colonic metabolome occur with reduced faecal iron availability. Lay summary Iron depletion by repeated venesection is the mainstay of treatment for haemochromatosis, an ironoverload disorder. Venesection has been associated with several health benefits, including improvements in liver function tests, reversal of liver scarring, and reduced risk of liver cancer. During iron depletion, iron absorption from the gastrointestinal (GI) tract increases to compensate for iron lost with treatment. Iron availability is limited in the GI tract and is crucial to the growth and function of many gut bacteria. In this study we show that reduced iron availability in the colon following venesection treatment leads to a change in the composition of the gut bacteria, a finding that, to date, has not been studied in patients with haemochromatosis.
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