Lecture 4- Intro To Microbiome Flashcards
(22 cards)
Exponential growth
X = 2n
X=Number of cells
n=number of generations
Xt = X₀ × 2ⁿ
Xt = the number of cells after growth
X₀ = the number of cells you started with
n = the number of generations (how many times the cells doubled)
Growing microbes
-grown in either liquid or on/in solid media
*solid medial = agar
*liquid media= broth
-content of the media + the conditions of incubation determine which organisms grow
*microbes are grown in either plates = called Petri dishes/ bottles
Plate cultures
*spread plate= sample is spread over the agar surface, bacteria grows on the surface
*pour plate= sample is placed on the plate and agar is poured over it, bacteria grows within the agar
-plates are inverted before incubation
-prevents condensation falling onto plates
Culture media
-mix of nutrients in solution
-contain nutrients used by microbes whe grow in laboratory
-contain buffer to maintain pH value
-liquid/ semi sold
Agar
- red algae polysaccharide
-used to make solid media
-rarely used as a nutrient
-remains solid over wide range of incubation conditions
-liquefies at approx 100 degrees, gels at approx 42 degrees
-microbes can be suspended in agar
Viable count
-common way of assessing growth of single celled organisms
-bacteria are grown on an agar plate; method relies on the fact that one bacteria can produce a colony large enough to be visible
Plating methods
- measure the number of viable cells
Plate dilutions of populations on suitable solid medium -> count number of colonies -> calculate number of cells in population
Simple and sensitive
Widely used for viable counts
Plate count
-each colony is formed from a single bacteria
-by counting the number of colonies= can determine the number of bacteria present
-^assumes microbes are suspended
-expressed as colony forming units; CFUs
Dilution
-samples can contain many millions of microbes
-if a plate is inoculated with too many microbes = too many colonies to count
-samples need to be diluted = ensures plates are countable; plates between 30-300 colonies
Serial dilution
-used to dilute samples in a consistent manner
-normally in 10 fold steps
-need to know the number of dilutions; to calculate the number of microbes in the original sample
Plating
-viable counts can be determined by= pour plates
-number of colonies are counted; plates between 30+300 used
The human microbe; intro
-human body; wide range of microorganisms= can have a positive/negative impact on health
Microbial strains
-every human carries their own strain which;
*are acquired early in life
*differ between environments and populations
*can persist for years
*undergo relatively rapid transitions
Host-microbiota interactions
-microbiome and their host constitute a highly integrated system; holobiont
-undergoes dynamic changes through time as it processes and responds to signals from the environment
*actively modulate development, nutrient absorption and disease onset
Normal microbiota
-transient flora may be present for days, weeks or months
*not permanent, form of contamination, potential infection risk & removed by washing
-resident microbiota permanently colonise the host; not removed by washing
Normal microbiota
-range of microorganisms
-evolves throughout life
-in a dynamic but stable balance; can be disrupted
Depends on; health, age, diet + climatic conditions
Located in; nose + throat, eyes, skin, large intestine and urinary + reproductive systems
-site specific distribution; different bacterial population between diff areas on the body
-develops from birth through childhood
Diversity in the human microbiome
-dominated by 4 phyla
*actinobacteria= gram +
*bacteriodetes= gram -
*firmicutes= gram +
*proteobacteria= gram -
Go through Vevox slides
10-15
32-38
Why cultures
Count numbers present
Identify the variety of microbes present
Detect presence of specific microbes
Isolate microbes with specific abilities; produce + degrade things
Calculating number present in the sample
Cfu/ml = colony count / dilution x volume plated
The 16s rNA gene
Codes for ribosomal RNA
Used for microbial identification
Universal, conserved, long enough to discriminate between species
Binary fission
How prokaryotes reproduce its asexual and creates 2 identical cells
Growth= more cells
Septum forms to divide the cell
Each split= one generation
Generation time = how long that takes
