Week 3 - Microbiology Bacterial Growth and Physiology Flashcards
Bacterial Gowth
Means multiplication… not bacteria getting bigger!
Bacterial repliation is the generation of 2 complete daughter cells from one cell
How to bacteria multiply?
Bionary Fission
Replication of DNA
Polar separation of daughter chromosomes
Generation of the cross-wall
Separation
What are steps of bacterial multiplication?
DNA Replication
Separation of daughter chromosomes
Cross wall generation
Separation
Static Antibiotics
Stops multiplication
Dynamic Antibiotics
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What is generation time?
The time for one bacterial cell to become two
This is also the time for a number of cells in a culture to double
What is doubling time?
Generation time
Bacteria in abcess vs bacteria in blood
Bacteria abcess dont grow ast fast so have to have longer acting antibactirea than bacteria in blood (grow really fast…)
What does bacterial growth curve look like?
If there was a slower growing bacteria species the exponential phase would have a lower slope*
Like bacteria growing in blood vs bacteria in an abscess (slower)
Lag phase is when bacteria are adapting to new environment
Log (growth phase) bacteria are doubling!
Stationary phase - nutreints are exahusted, toxins build bacteria remain in constant number
Death phase - toxins kill bacteria (not in all bacteria)
How is this graph different in abcess vs blood?
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Why want to colonize bacteria?
If someone has UTI.. we want to know how many bacteria are in it… so take sample of urine and colonize it
How to determine bacterial concentration by serial dilution and colony and colony forming units (CFU)?
To determine concentration of bacterial from a liquid culture.. Culture is diluted and plated onto media
Each colony represents ONE bacterium from original culture
For a given culture.. at each time point
Make 10-fold dilutions of a culture
Spread a known volume on an agar plate
Allow colonies to grow
Count number of colonies
Calculate original concentration (at time of sampling)
This only represents LIVE (VIABLE) bacteria
What are growth requirements for bacteria? What does it depend on?
Depends on genetic information in bacteria
All of the elements for organic matter
Ions for energy generation, catalysts, and osmotic maintenance
Energy from Fermentation
Anaerobic bacterial use this.. why? because if they are exposed to O2 they die
The formation of ATP is not coupled to electron transfer (Electron transport chain)
Energy from Respiration
Formation of ATP via oxitative phosphorylation (chemical reduction of an oxidant) where ATP is formed during electron transfer
Energy from Photosynthesis
No medically important bacteria here.
ATP is formed via reduction of an oxidant via light energy
Fermentation
Can use the products of fermentation to identify bacteria**
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What are nutritional requirements for bacteria?
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Heterotroph
majority of bacteria*
Requires pre-formed organic compounds like sugars, amino acids, and vitamins
Autotroph
Can synthesize everything it needs from inorganic compounds like CO2
Hypotroph
Is an oblicgate intracellular pathogen requiring the host to provide organic compounds - can also be called an intracellular heterotroph
What are three types of bactria based on nutritional req’s?
Heterotroph
Autotroph
Hypotroph
How can bacteria uptake nutrients?
Diffusion through cytoplasmic membrane: Three ways
Carrier mediated diffusion (facilitated diffusion)
Phosphorylation-linked transoprt (group translocation)
Active transport
Permease
Carrier protein to aid uptake of nutritients through plasma membrane
Carrier Mediated Diffusion
Facilitated diffusion - Nutrients travel across membrane due to concentration gradient
Conentration dependant
Not energy dependant
Phosphorylation - linked transport
Group translocation
Energy dependent
Some sugars are taken up this way
Sugars are co-transported with a carrier and phosphorylated in the process
Active Transport
Energy dependent
Requires generation of proton-motive force
Protons pumped out of cell, creating flux of protons in and out of organism
Molecules are coupled to uptake of protons making overall energetics favorable
Requires a symport for the uptake of protons and the nutrient
Obligate aerobes
Must have O2 for growth
Obligate anaerobes
No requirements of O2
Usually killed by O2 radicals
Faculative Anaerobes
Can grow with or without O2
Microaerophilic
Must grow at low concentrations of O2 (less than 20%)
Aerotolerant anaerobes
Similar to facultative but prefer anaerobic (fermentative) growth
What is superoxide dismutase?
Removes radicals
Which, facultative or anaerobic organism, in abcess
facultative because can grow with or without O2…
Growth location based on gaseous requirement
Psychrophiles
Grow best in range of 0-20C
Mesophiles
Grow best in range of 20-45C
Most bacteria… we deal with
Thermophiles
Grow best in range of 45-90C
Bacterial growth media
Basid growth req’s for bacteria must be simulated in lab
Liquid media is a broth
Solid is broth + 15% agar
Defined media is made with chemicals at know concentrations
Defferential Media
Supplies nutrients and indicators (pH or RBC) for visual determination of which organisms are present
Betahemolytic strep.. Can put in solid cultrure with RBCs. Can see if it lyces RBCs and visually diagnose
Selective media
Selects AGAINST growth of particular bacteria by addition of dyes, acid/base, salts, or antibiotics
MacConkey Agar
Both Differential and Selective Media
MacConkey Agar: Bile salts and Crystal Violet
Inhibit growth of gram POS (selective) and has lactose plus a pH indicator to indicate the fermentation of lactose (differential)
