5.8 - Growth of Bacteria Flashcards
Define Colony
Population of cells arising from a single cell of endospore, or from a group of attached cells.
Define pure culture
Only one species or strain of bacteria
-Aids in ID by characteristic colony color, shape, texture, size
Define mixed culture
Multiple strains or species of bacteria
Explain Obligate Aerobes oxygen use and if they have SOD and Catalase
Have both SOD and Catalase
Example: Mycrobacterium tuberculosis
Explain Facultative anaerobes oxygen use and if they have SOD and Catalase
have both SOD and Catalase
Example: Escherichia coli
Explain Microaerophiles oxygen use and if they have SOD and Catalase
- Damaged by normal atm. levels O2 levels (above 20%), needs 2-10% O2 levels
- Usually has SOD and Catalase in very low concentrations
- Example Helicobacter pylori
Explain Obligate/Strict anaerobes oxygen use and if they have SOD and Catalase
Usually lack both SOD and Catalase
Example: Clostridium
Explain Aerotolerant anaerobes oxygen use and if they have SOD and Catalase
- Ignore O2
- Usually have SOD and lack Catalase
- Example: Propionibacterium acnes
Superoxide Dismutase oxygen derivatives reaction equation
2 (02) + 2H –> O2 + H202
Catalase oxygen derivatives reaction equation
2 H2O2 –> 2 (H2O) + 02
Define Fastidious
If the bacteria requires many micronutrients or growth factors, they are considered fastidious
Define Complex media
Supports growth of wide variety bacteria
-Example nutrient agar
Define Enriched media
Addition of sterols, blood, serum, serum, egg yolk
Example: Sheep blood agar, Chocolate agar
Sheep blood agar used for?
Most clinically important Gr+ and Gr-
Chocolate agar used for?
- Heated lysed blood
- Fastidious organisms such as Neisseria gonorrhoea or Haemophilus influenzae
Define Selective Media
Ingredients that inhibit growth of some organisms but allow others to grow
Mannitol Salt Agar (MSA)
- High Concentration of NaCl (7.5%)
- Inhibits growth of most organisms but permits staphylococci to grow.
- Yellow color on altar indicates the bacterial species can ferment mannitol.
MacConkey agar
- Bile salts, dye crystal violet
- Inhibits growth of gram positive bacteria and selects for gram negative (but not fastidious gram negative)
- Lactose fermenters and pH indicator, allows for differentiation of Gram negative based on their ability to ferment lactose (turns pink for lactose fermentors)
What are the four stages of the bacterial growth curve?
Lag, Log, Stationary, and Death phases
Define Lag phase of bacterial Growth curve?
Cells synthesizing new macromolecules
Define Log phase of Bacterial Growth curve?
- Cell growing and dividing at maximal rate possible given their genetic potential and the local environment.
- Dividing and doubling at regular intervals.
Define Stationary Phase?
- Total number of viable cells remains constant.
- Nutrient limitation, accumulation of toxic wastes, depletion of O2.
- Endospore formation
- Secondary metabolite synthesis. e.g. toxins, antibiotics
Define Death Phase?
Decrease in number viable cells often exponential
What is the best phase for harvest of useful products in the bacterial growth curve?
Stationary phase
Which phase in the bacterial growth curve is the least resistant to antibiotics?
Stationary phase
What phase in the bacterial growth curve is the most sensitive to antibiotics?
Log/Lag
What phase is has the most DNA replication?
Lag phase
What phase involves the plasma membrane?
Log phase
What is the primary way that bacteria get cellular energy?
Oxidizing carbs.
-Glucose is the most common carb, proteins and lips can also be used.
What are the main to ways to get energy from carbohydrates?
Cellular respiration and fermentation
Which method of anaerobic bacteria of medical importance use what method of energy production?
Fermentation
Define Glycolysis
- Any metabolic process that releases energy from a sugar or other organic molecule, does not require O2, (but can occur in the presence of O2) or an electron transport system, and uses an organic molecule as the final electron acceptor
- Does not use Krebs cycle or E.T.C.
Main points of Prokaryotic anaerobic respiration?
- Energy generating mode for some anaerobic bacteria
- Inorganic compounds other than O2 serve as final acceptors (Ex: Nitrate)
- Can be used as an alternative to aerobic respiration in facultative organisms.
- Yields less energy than aerobic respiration.
How many ATP molecules are produced during fermentation?
1) 1-2 ATP
2) Most energy from starting material remains in bonds of organic end products… thus not completely oxidized.
Define Biofilm as a virulence strategy?
1) Antibiotic-resistance strategy
2) 65-80% human infections developed countries
3) Examples: Caries, gingivitis, periodontitis, otitis media, sinusitis, prostatitis, native valve endocarditis, chronic Pseudomonas aeruginosa infections in cystic fibrosis, catheter/shunt infections, heart valve/prosthetic implant infections
What is planktonic phenotype?
‘Free floating’, may be motile
What changes to the bacteria happen once a biofilm is formed?
- Attached to a surface, loss of flagella.
- They are sticky, slimy, and tenacious.
Are biofilms made of only one type of bacteria?
No, they are mixed, heterogeneous, dynamic, slime covered cities.
