how we cultivate bacteria L4 Flashcards
what do bacteria need to grow
gases, moisture, nutrients, temperature, ph, correct ionic balance (salt)
how do bacteria produce and consume energy to allow growth
utilisation of metabolic reactions
Catabolic - energy releasing reactions
Anabolic - building energy into food
To achieve this bacteria need nutrients
what are the two types of nutrients
macronutrients and micronutrients
what are the 4 macronutrients and what do they provide
carbohydrates, proteins, lipids, nucleic acids
provide the elements needed for growth when they are broken down
what elements do bacteria need to grow and what are they used in
carbon- 50%: sugars and amino acids
oxygen- 17%: H20 or O2
nitrogen- 13%: DNA, amino acids
phosphorus- 2.5%: DNA
nutrients provided through liquid or solid broth called media
describe the two types of media
- chemically defined media
- control concentrations of each element precisely
- remove or add elements to see how it effects growth - undefined complex media
- has everything needed for bacteria to grow
what does undefined complex media contain
tryptone, yeast extract, NaCl
how can you measure bacterial growth
- population density
- population number
what can you calculate from analysing population number and population density
- growth rate
- generation time
what are 2 ways you can measure bacterial growth
- spectrophotometer: measures population density
- includes dead or debris so less sensitive
to be more sensitive, measure population number - colony forming units: measures population number
- may underestimate for cells in chains or clusters
- slow
exponential growth graph can be turned to linear log graph
what is the equation to work out final cell number after growth of a culture
N = N02to the power of n
N: final cell number
N0: initial cell number
n: number of generations
what is the equation for generation time
g = t/n
g: generation time
t: duration of exponential growth
n: number of generations
why is knowing generation time useful
Compare different bacterial species growing in the same condition
Compare one species grown in different conditions
Can also be used to show your data is statistically significant (or not
what environmental factors influence bacterial growth
temp, ph, oxygen availability, salinity
what are extremophiles
bacteria that can grow under harsh conditions that would kill other bacteria
The temperature ranges that bacterial species grow at varies considerably
what is the temperature ranges for mesophiles
min: 10 degress
optimum: 39
max: 46
when above optimum, proteins denature causing growth to reduce steeply
bacteria grow in a range but possess an optimum
Optimum pH is based on extracellular environment only
as Ph of batch changes often, what is needed
buffer in the media
Na2HPO4 and KH2PO4 are excellent buffers
what is optimum ph for E.coli
7
- water
how does Salinity effect growth
nonhalophile (e.coli): hate salt
halotolerant: can survive in low salt concentrations
halophile: can survive in low salt concentrations
extreme halophile: survive in high salt concentrartions
how does oxygen effect growth
aerobic need oxygen to grow, other do not
what is chemostats
this is a continous culture
fresh media is added and waste is removed
Once equilibrium is obtained: volume, population density, growth rate and metabolic state remain constant
bacteria growth is in steady state
All culture parameters remain constant
motor keeps bacteria agitated
how is dilution rate and growth rate (µ) related
dilution rate should be equal to growth rate
- bacteria that is washed out is same that is washed in
how is dilution rate worked out
dilution rate= flow rate/volume
What would happen if the Flow Rate (F) exceeded Growth Rate
too many nutrients and bacteria would not be able to grow fast enough
- should wash out bacteria
what would happen if the flow rate is below growth rate
not enough nutrients so bacteria may struggle to grow
- enter stationary phase
what is MICROFLUIDICS
An emerging technology aiding the understanding of bacterial physiology
Build an agar pad with tracks to hold cells in some form of order instead of looking at messy division under microscope
Bacteria grows along the ridges
