Browsing Food Biosciences by Funder "Irish Research Council"
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Antibiotic Resistance in the Gut MicrobiotaAntibiotic resistance is an increasing threat to our ability to treat infectious diseases. Thus, understanding the effects of antibiotics on the gut microbiota, as well as the potential for such populations to act as a reservoir for resistance genes, is imperative. This thesis set out to investigate the gut microbiota of antibiotic treated infants compared to untreated controls using high-throughput DNA sequencing. The results demonstrated the significant effects of antibiotic treatment, resulting in increased proportions of Proteobacteria and decreased proportions of Bifidobacterium. The species diversity of bifidobacteria was also reduced. This thesis also highlights the ability of the human gut microbiota to act as an antibiotic resistance reservoir. Using metagenomic DNA extracted from faecal samples from adult males, PCR was employed to demonstrate the prevalence and diversity of aminoglycoside and β-lactam resistance genes in the adult gut microbiota and highlighted the merits of the approach adopted. Using infant faecal samples, we constructed and screened a second fosmid metagenomic bank for the same families of resistance genes and demonstrated that the infant gut microbiota is also a reservoir for resistance genes. Using in silico analysis we highlighted the existence of putative aminoglycoside and β-lactam resistance determinants within the genomes of Bifidobacterium species. In the case of the β- lactamases, these appear to be mis-annotated. However, through homologous recombination-mediated insertional inactivation, we have demonstrated that the putative aminoglycoside resistance proteins do contribute to resistance. In additional studies, we investigated the effects of short bowel syndrome on infant gut microbiota, the immune system and bile acid metabolism. We also sequenced the microbiota of the human vermiform appendix, highlighting its complexity. Finally, this thesis demonstrated the strain specific nature of 2 different probiotic CLA-producing Bifidobacterium breve on the murine gut microbiota.
Characterization of protein hydrolysates from blue whiting (Micromesistius poutassou) and their application in beverage fortificationEnzymatic hydrolysis of fish proteins has been employed as a principle method for converting under-utilised fish into valuable products for the pharmaceutical and health food industries. In this study, six commercial enzymes were tested for their ability to make fish protein hydrolysate powders from whole blue whiting. The chemical and functional properties of these powders were compared. The powders all had high solubility (>80%) across a wide pH range in water and their solubility improved further within a vitamin-tea beverage matrix (>85%). Varying degrees of anti-oxidant activities were recorded for the powders using three model systems (DPPH, ferrous chelating and reducing power). This study demonstrates that commercial enzymes are useful for the extraction and alteration of fish protein from a low value source to produce highly digestible, low molecular weight peptide powders that could be used as a fortifying health ingredient, especially in beverages.
A degenerate PCR-based strategy as a means of identifying homologues of aminoglycoside and ß-lactam resistance genes in the gut microbiotaBackground: The potential for the human gut microbiota to serve as a reservoir for antibiotic resistance genes has been the subject of recent discussion. However, this has yet to be investigated using a rapid PCR-based approach. In light of this, here we aim to determine if degenerate PCR primers can detect aminoglycoside and β-lactam resistance genes in the gut microbiota of healthy adults, without the need for an initial culture-based screen for resistant isolates. In doing so, we would determine if the gut microbiota of healthy adults, lacking recent antibiotic exposure, is a reservoir for resistance genes. Results: The strategy employed resulted in the identification of numerous aminoglycoside (acetylation, adenylation and phosphorylation) and β-lactam (including bla OXA, bla TEM, bla SHV and bla CTX-M) resistance gene homologues. On the basis of homology, it would appear that these genes originated from different bacterial taxa, with members of the Enterobacteriaceae being a particularly rich source. The results demonstrate that, even in the absence of recent antibiotic exposure, the human gut microbiota is a considerable reservoir for antibiotic resistance genes. Conclusions: This study has demonstrated that the gut can be a significant source of aminoglycoside and β-lactam resistance genes, even in the absence of recent antibiotic exposure. The results also demonstrate that PCR-based approaches can be successfully applied to detect antibiotic resistance genes in the human gut microbiota, without the need to isolate resistant strains. This approach could also be used to rapidly screen other complex environments for target genes.