The impact of iron on the function and composition of the human gut microbiota

Parmanand, Bhavika (2019) The impact of iron on the function and composition of the human gut microbiota. Doctoral thesis, University of East Anglia.

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Abstract

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. Assessing iron bioavailability and the effects on bacterial groups is an evolving subject area and forms the basis of the research presented in this thesis.
The growth of Escherichia coli and Salmonella Typhimurium was significantly impaired when cultured independently in iron-deficient media (p<0.0001). These observations positively correlated with a decrease in water-soluble iron concentrations present in the culture. However, depletion of iron did not affect the growth of the beneficial species, Lactobacillus rhamnosus.
Culturing human faecal microbiotas in an in vitro colon model identified changes in the growth of different bacterial taxa. 16S rDNA-based metataxonomics indicated that under conditions of iron depletion through BPDS, a chemical iron chelator, the relative abundance of several taxa decreased, including a 10% and 15% decrease in Escherichia and Bifidobacterium, respectively. This was supported by observations of lower viable counts of Enterobacteriaceae and bifidobacteria. Analysis using 1H NMR indicated that the production of acetate, butyrate and propionate in vitro was reduced under iron-restricted conditions. Iron chelation through phytin, a dietary compound, illustrated similar results with the exception of a 33% increase in the relative abundance of Bifidobacterium and 225% increase in Collinsella. Furthermore, increases in propionate and formate concentrations were also observed when cultured with phytin.
A 6-week, crossover double-blinded randomised human dietary intervention trial was performed (n=14), where participants were asked to consume encapsulated phytin or placebo. Capsules were coated with a specialised formulation, Phloral®, designed to release phytin directly in the colon. No conclusions could be made regarding the iron chelating properties of phytin as analysis of stool samples collected revealed clumps of phytin and therefore, unsuccessful dispersal of phytin within the colonic lumen. This pilot human intervention study indicates that the form of phytin is an important factor and this should be considered for follow-up studies.

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Medicine and Health Sciences > Norwich Medical School
Depositing User: Zoe White
Date Deposited: 08 Jan 2020 14:28
Last Modified: 08 Jan 2020 14:28
URI: https://ueaeprints.uea.ac.uk/id/eprint/73555
DOI:

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