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Lecture notes HUB2019F - Microbiome and Diarrhoea
- Course
- HUB2019F
- Institution
- University Of Cape Town (UCT)
Microbiome and Diarrhoea
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🟥Microbiome and Diarrhoea
Wednesday, 18th May 2022
The Intestinal Microbiome:
The microbiome is the collective genomes of the micro-organisms in a particular
environment.
Microbiota is the community of micro-organisms themselves, while microbes
include archaeological, viruses, phages, yeast, fungi and more importantly
bacteria.
Microbes communicate with human cells like the enterocytes and immune
cells where microbes produce metabolites and neurotransmitters.
There are 100 trillions microbes mainly in the gut with over a thousand species.
The genome of the human genome has 23000 genes while the microbiome
is 3.3 millions genes.
It acts as a virtual organ.
Most bacteria are killed in the stomach and small intestine by lysozymes,
defensins, HCl or protein-digesting enzymes.
They are present from the mouth to the colon, where the colon is a stable
environment where it is kept via slow motility, lower pH, O2 levels and the
ileocecal valve.
Establishing the Microbiome:
The intestines are thought to be sterile at births where bacterial colonisation
occurs from birth onwards where the adult-type microbiome is formed by 2~3
years after birth, which is stable and resilient against large changes.
This diversity and stability is reduced as we age.
Changes in diet are the main causes of microbiome change.
The microbiome consists of around
Microbiome and Diarrhoea 1
, 6~7 different bacterial phyla.
There is a vast degree of variation
between individuals.
The enterotype is defined by the
presiding bacterial genus (like
Bacteroides → red meat diets or
Prevotella → vegan diets).
Interactions with the Host:
Interactions:
Commensal where there is the co-existence without any harm, where one
benefits.
Mutualistic where both organisms benefit.
Parasitic where one benefits and the other is harmed (pathogenic).
Bacteria ferment non-digestible substrates that we can then take up via the
production of short fatty acids (fibres and short polysaccharides → short chain
fatty acids).
They provide energy for the colonocytes, prevents carcinogenesis, maintains
the anaerobic colon conditions via the oxidation of these SCFAs.
It maintains the slightly acidic pH and regulates gluconeogenesis and satiety.
The production of vitamins like folate, K, B12 and biotin.
Contributions to bile-acid metabolism, production of anti-oxidants, alter
polyphenol bioavailability or the activation of certain compounds.
Maintains a well-functioning innate immune response and improves mucosal
barrier function.
There are harmful effects that include the production of carcinogens and toxins,
the activation of inflammation and infection via bacterial compounds and the
alteration of gut hormones and energy homeostasis (obesity).
Dysbiosis:
This is an imbalance in bacteria
associated with disease or the skewing
Microbiome and Diarrhoea 2
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