Microbio Chapter 6- Microbial Growth Flashcards
What factors determine growth of prokaryotes?
Temperature
pH
Osmotic pressure
Oxygen
Which of the growth factors are physical factors?
Temperature
pH
Osmotic pressure
Which of the growth factors is a chemical factor?
Oxygen
What are the three primary groups made on the basis of their preferred temperature?
- Psychrophiles
- Mesophiles
- Thermophiles
What general temperature do psychrophiles prefer?
Cold temps
What general temperature do mesophiles prefer?
Moderate temps
What general temperature do thermophiles prefer?
Hot temps
What are the two divisions of psychrophiles?
True
Pyschotrophs
What temperature can True psychrophiles start to grow?
0 degrees celsius
What is true psychrophiles optimum temperature?
15 degrees celsius
What temperature can true psychrophiles not grow at?
20-25 degrees celsius
Do true psychrophiles cause disease?
No they are non-pathogenic
What is the other name for pyschrotrophs?
Falcutative
What temperature can pyschrotrophs start to grow?
0 degrees celsius
What is pychrotrophs optimum temperature?
20-30 degrees celsius
What temperature can pyschrotrophs not grow at?
30 degrees celsius
What do Psychrotrophs often cause?
Food spoilage even when refrigerated its just slowly degrades food
-mold, odour,slime
What temperatures can Mesophiles start to grow?
25-40 degrees celsius
What is Mesophile sotimum temperature?
37 degrees celsius
What temperature can Mesophiles not grow?
50 degrees celsius
Are Mesophiles disease causing?
Yes they are pathogens
What are the two types of Thermophiles?
Thermophiles
Hyperthermophiles
What temperature can thermophiles NOT grow at?
Any temperature below 45 degrees celsius
What are thermophiles optimum temperature?
50-60 degrees celsius
What is the maximum temperature thermophiles can grow at?
70-80 degrees celsius
Are thermophiles disease causing?
No, they are non-pathogenic
What temperature can hyperthermophiles NOT grow at?
Any temperature below 45 degrees celsius (same as thermophiles)
What are hyperthermophiles optimum temperature?
50-60 degrees celsius (same as thermophiles)
What is the maximum temperature hyperthermophiles can grow at?
110-121 degrees celsius
Are hyperthermophiles disease causing?
No, they are non-pathogenic
how does pH affect prokaryotes growth?
Too basic or too acidic will denature stop the bacteria from growing
What the pH range that most bacteria grow best in?
ph 6.5- 7.5 (neutral)
What are acidophiles?
Bacteria tolerable to acidity (low pH)
How does osmotic pressure affect cell growth?
Too little or too high concentrations of solute concentrations can inhibit growth
How does a hypertonic environment affect cell growth?
The solution/environment has higher concentration of solutes then inside the cell causes water to leave the cell and makes the cell shrink
What is isotonic?
Solute concentration outside the cell is equivalent to the solute concentration inside the cell
What is hypotonic?
Solute concentration outside the cell is lower than the solute concentration inside the cell
How do hypotonic/ low osmotic pressure affect cell growth?
Water enters the cell and microbes with weak cell walls with be lysed 9prevent growth)
How do high concentrations of sugar or salt affect cell growth?
Increase osmotic pressure = hypertonic
Water leaves the cell and prevent growth
How does energy extraction differ between aerobes and anaerobes?
Aerobes (use oxygen) extract more energy from nutrients
What are organisms that require oxygen for growth called?
Obligate aerobes
What enzymes do obligate aerobes have present?
Enzymes catalase and SOD
What does enzymes catalase and SOD do?
Neutralize toxic forms of oxygen
What are organisms that are anaerobic and aerobic called?
Facultative Anaerobes
Where do facultative anaerobes have greater growth?
In the presence of oxygen
What enzymes do facultative anaerobes have present?
Enzymes catalase and SOD
What is the name of organisms who only grow in the absence of oxygen?
Obligate Anaerobes
What enzymes do obligate anaerobes have present?
NO enzymes
-cannot tolerate any form of oxygen
What is the name of organisms who only grow in anaerobically but growth will continue in presence of oxygen?
Aerotolerant Anaerobes
What enzyme do aerotolerant anaerobes have present?
Only SOD
What occurs if only one enzyme is present?
Toxic forms of oxygen are partially neutralised
What are organisms called that only grow in low oxygen concentrations?
Microaerophiles
What happens if Microaerophiles are exposed to normal atmospheric oxygen?
They will produce lethal amounts of toxic forms of oxygen
What bacteria are obligate aerobes?
Most bacteria
What bacteria are obligate anaerobes?
Clostridium
What is an example of a facultative anaerobe?
Escheria coli
What kind of respiration do Aerotolerant anaerobes use?
Fermentation
-Obligate fermenters
What is an example of an Aerotolerant anaerobe?
Lactobacilli
What are example of microaerophiles?
Helicobacter pylori
Complyobacter jejuni
What does Helicobacter pylori cause?
Stomach ulcers
What does Complyobacter jejuni cause?
Gastroenterillis
What are the toxic oxygen forms?
Singlet oxygen 1O2-
Superoxide Radicals or Anions (free radicals) O2-
Peroxide anion O2 2-
Hydroxyl radical OH-
What is singlet oxygen?
Normal molecular oxygen that has been boosted into a higher-energy state
-Extremely reactive
What are superoxide free radicals?
Very unstable (Steals electrons from neighbouring molecules and becomes a radical)
What neutralises Superoide free radicals?
SOD: Superoxide dismutase
What bacteria have SOD?
Obligate aerobes
Facultative anaerobes (when growing aerobically)
Aerotolerant anaerobes
How does SOD neutralise superoxide free radicals?
SOD converts superoxide radical into molecular oxygen (O2) and hydrogen peroxide (H2O2)
What is the reaction equation for SOD neutralising superoxide radicals?
O2- + O2- + 2H+ —> H2O2 + O2
How are superoxide radicals produced?
Formed in small amounts during normal aerobic respiration or by obligate anaerobes in the presence of oxygen
How are peroxide anions formed?
The hydrogen peroxide produced during the neutralisation of Superoxide radicals by SOD contains peroxide anions (produced during aerobic respiration)
What has peroxide anions as an active principle?
Antimicrobial agents
e.g, Hydrogen peroxide and benzoyl peroxide
What enzymes neutralises peroxide anions?
Enzyme catalase and peroxidase
How does catalase neutralise peroxide anions?
Converts it into water and oxygen
How does peroxidase neutralise peroxide anions?
Converts it into only water (no oxygen)
What is the reaction equation for catalase?
2 H2O2 —> 2H2O + O2
What is the reaction equation for peroxidase?
H2O2 + 2H+ —> 2H2O
How are hydroxyl radicals formed?
Ionizing radiation and trace amounts are produced by most aerobic respiration
What is the most reactive form of toxic oxygen?
Hydroxyl Radicals (OH)
How are toxic oxygen forms important to phagocytosis?
When Phagocytes ingest pathogens the toxic forms kill them
What is used to grow bacteria on a solid medium?
Nutrient agar
At what temperature does Agar liquify?
100 degrees celsius
At what temperature does Agar solidify?
37 degrees celsius
What happens when the Agar is heated to 100 degrees?
Sterilization
Why is sterilisation important fro culture media?
Allows it to be stored for longer periods
Why is agar used?
Bacteria cannot metabolise it
What is the name of the method when agar is used?
Streak plate method
Why is the streak plate method used?
Isolates pure cultures
-Specific
What is a pure culture?
Contains only one species or strain
What is the tube/broth method?
Bacteria is grown in a nutrient broth in a test tube
What are the pros and cons of the broth method?
Pro- Grows quickly
Con- Less specific (Can’t make a diagnosis
What are the kinds of media?
Selective media
Differential media
Selective and Differential media
What agar is used for selective media?
Bismuth sulfite agar
What is the purpose of selective media?
Supresses unwanted microbes and encourages desired microbes
-only one colony appears
What is an example of a bacteria encouraged to grow by selective media?
Salmonella typhus
What does Salmonella typhus cause?
Typhoid fever
What agar is used for differential media?
Blood agar
What is the purpose of differential media?
Makes it easy to distinguish colonies of different microbes on the same plate
What is an example of bacteria grown using differential media?
Streptococcus pyogenes
Invasive group A
What does Streptococcus pyogenes cause?
Strep throat
Why is blood agarused?
It contains RBC and can detect bacteria that lyses blood cells (Hemolysis)
Hemolysis will result in a clear zone
What agar is used for selective and differential media?
Mannitol salt agar
What is the purpose of using selective and differential media?
You suppress unwanted microbes and can distinguish colonies
What is an example of bacteria grown using selective and differential media?
Staphylococcus aureus
What does Staphylococcus aureus cause?
Skin infections, toxic shock and food poisoning
what is binary fission?
method of cell division for microbial growth
What is generation time?
Time required for a cell to divide (population doubles)
What is the formula for generation time?
60 min x Hours / number of generations
What is the lag phase?
Phase #1
Intense activity, population prepares for growth
no growth actually occurs
What is log phase?
Phase #2
Logarithmic increase in population
Binary fission occurs
What is the stationary phase?
Phase #3
Equilibrium
Microbial deaths are equal to production of new cells
What is the death phase?
Phase #4
Logarithmic decline
Population decreases at logarithmic rate
