Bacterial Growth Flashcards
What is bacterial growth ?
bacterial cells build up protoplasm and double in size
- once doubled each of its parts the cell divides into 2 daughter cells
What is binary fission ?
when a cell divides into 2 daughter cells
- a way that bacteria reproduce
What needs to duplicate in binary fission before the cell can divide ?
prokaryotic chromosome
How do we measure bacterial growth ?
by the increase of number of bacterial cells
What are the different methods of measuring bacterial growth ?
- calibration
- pour plate/spread plate method
How does the pour plate method work ?
- inoculate empty plate
- add melted nutrient agar
- swirl to mix
- colonies grow in and on solidified medium
- use either 1.0 or 0.1 ml
How does a spread plate method work ?
- inoculate plate containing solid medium
- spread inoculum over surface evenly
- colonies grow only on the surface of the medium
- liquid can’t be easily soaking up on the solid medium
- can only use about .1 ml
In what cases would we use serial dilution ?
when working with very contaminated samples
- want isolated colonies
What is a dilutant ?
liquid that is sterile that has no bacteria in it
Why do we want isolated colonies ?
so they are easily identifiable and can see how bacteria are growing on the plate
- more qualitative then quantitative
- you can tell if you have a pure or mixed culture
- want to see individual/isolated colonies in serial dilutions
Why would someone do a streak plate ?
lets you isolate a single type of bacteria
- you spread out the parent bacteria into 4 quadrants so that the bacteria gradually become more isolated in each quadrant
- in 4th quadrant you should have isolated colonies
Why is isolating bacteria important ?
want to see how the bacteria grow on the plate and to identify them
What does the minimum temp of a bacteria mean ?
the lowest temp that permits growth
What does the maximum temp of a bacteria mean ?
highest temp that permits growth
What does the optimum temp of a bacteria mean ?
range of temp that promotes the highest growth rate
Is the min, max, and optimum temp of each bacteria the same ?
no
- bacteria grow over a range of temps
What are the 4 temp groups that bacteria grow in ?
psychrophiles, mesophiles, thermophiles, extreme thermophiles
What are psychrophiles ?
- optimum between 5-20 C
- like cooler temps like snow fields, polar ice or ocean depths
- Ex.) flavobacterium spp
What are mesophiles ?
- optimum between 20-50 C
- the temp that our human pathogens and majority of bacteria like
What are thermophiles ?
- optimum between 50-80 C
- like it hot
- Ex.) bacteria in habitats exposed to sun, or in hot springs; bacillus stearothermophillus
What are extreme thermophiles ?
- optimum between 80 C and above
- like it very hot
- ex.) can find in soil and water associated with volcanic activity
Describe Obligate (strict) aerobes
- must have O2 to grow
- use respiration to get energy
- ex.) pseodomonas aeruginosa
Describe Obligate (strict) anaerobes
- cannot grow in the presence of O2
- use fermentation to get energy
- ex.) bacteroides fragilis
Describe Facultative anaerobes
- prefer to grow in O2 but can grow without O2
- uses both fermentation and respiration
- happens optionally in response to circumstances rather then by nature
Describe Microaerophilic organisms
- need O2 in small amounts yet will die without O2
- ex.) helicobacter pylori, and Neisseria gonorrhoeae
Describe Aerotolerant organism
- grows with or without O2 (O2 has no impact on growth)
- growth occurs evenly throughout culture tube
- ex.) streptococci species
What type of bacteria doesn’t have a detoxifying pathway ?
anaerobic bacteria
- since they can’t detoxify then bacteria will die
What type of bacteria has a detoxifying pathway ?
aerobic or facultative bacteria
- since they can detoxify they can turn that into nontoxic products like H2O and O2
What nutrients are required for bacterial growth ?
need source of Carbon from catabolized organic molecules like
- proteins, carbs, fatty acids, amino acids, etc
Where does the energy come from for bacterial growth ?
from “redox” (reduction and oxidation) reactions
- primary energy source is glucose metabolism
What are other sources required for bacteria growth ?
vitamins, minerals, and water
- need hydrogen ions which they get from the water
What are the phases of the bacterial growth curve in order ?
- lag phase
- exponential/log phase
- stationary phase
- death phase
What occurs in the lag phase ?
bacteria is adjusting to new environment before reproduction and needs time to adapt
- cells not reproducing at max rate
What occurs in the exponential/log phase ?
start to divide rapidly, going through binary fission very quickly
- reproduction at max rate
- growth continues as long as nutrients and space is sufficient and environment is favorable
What occurs in the stationary phase ?
bacteria is going to stop growing so rapidly and the curve will flatten out
- decline in growth
- increase in death
What occurs in the death phase ?
population starts to go down rapidly
- gone through all their resources and have no room to grow anymore
- toxins might be built up in environment
What happens in a closed system in relation to bacterial growth curve ?
- nutrients and space are limited
- the waste products stay in there and can toxify the environment and cause harm to the bacteria since there is no mechanism to remove it
