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Title: Microbiology
Description: Lecture notes covering probiotics, the gut microbiome and microbial growth Second year undergraduate level
Description: Lecture notes covering probiotics, the gut microbiome and microbial growth Second year undergraduate level
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Microbiology revision notes
Lecture 1 – Probiotics
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Probiotics = live microorganisms which when administered in adequate amounts,
confer beneficial health effects on the host
Gut microbiome :
-‐ 10!" microbes (1kg)
-‐ 3000 bacterial species: Gram+, Gram-‐, sulphate reducing bacteria,
archaebacteria, yeast, protozoa -‐opportunistic/bad eg Staphylocci – beneficial
eg lactobacilli –
-‐ most metabolically active
Probiotic culturing
-‐ Isolate in selective media: anaerobically eg bifidobacteria, microaerophically
(low oxygen) eg lactobacilli and aerobically eg bacillus
-‐ Identify using 16S ribosomal RNA gene (conserved + 9 variable regions) (part
of all bacteria) – to discriminate taxa at species level
Properties of probiotics
-‐ contain sufficient live active bacteria
-‐ survive stomach/bile acids
-‐ provide health benefits
-‐ safe and amenable for human consumption
Beneficial
-‐ chronic allergies (eczema), inflammatory bowel disease, diarrhea, NEC
(neonatal necrotic enterocolitis)
Food poisoning
-‐ Clostridium perfrigens – food poisoning in humans
-‐ necrotic enteritis NE in poultry
-‐ banning of antibiotic growth promoters (AGPs) – NE more prevalent
-‐ Competitive exclusion: Early establishment of a mature bacterial flora
in the intestines of newly-hatched chicks confers/provides an adult
level of protection against enteropathogens - eg exclusion of
clostridium perfrigens in birds (when lactobacillus was given before
giving clostridium perfringens, less intestinal lesions compared to
without lactobacillus
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01 – Microbial growth
• Prokaryotics divide by binary fission
- 2 daughter cells separated by equatorial septum
- exponential growth – bacteria growth rate proportional to
population size
- except cyanobacterium – enlarge and suddenly divide many times
with separating
- divide at constant interval (length of interval depends on species,
growth medium,pH, temp) = generation or doubling time 𝑁! x 2!
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Stages of growth
- Lag – prepare for growth – time to detect new environment
- log/exponential – constant maximum rate of growth – metabolites
(enzymes)-downshift or upshift
- late log – growth slows – quorum sensing (sending and receiving
signals to detect presence of other cells)
- stationary – stop growth at 10^9cells/ml-physiological stages
(spores, reduce cell size, more resistant)
- death – toxic products – negative exponential
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continuous culture
- exponential phase for longer
- medium constantly added and removed -‐imput needs to equal output= dilution
rate
Examples
- Clostridium perfringens
- E
Title: Microbiology
Description: Lecture notes covering probiotics, the gut microbiome and microbial growth Second year undergraduate level
Description: Lecture notes covering probiotics, the gut microbiome and microbial growth Second year undergraduate level