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Questions and Answers
What is the preferred pH range for most microorganisms?
What is the preferred pH range for most microorganisms?
Which group of microorganisms prefer a pH of >8.5?
Which group of microorganisms prefer a pH of >8.5?
What is the characteristic pH range for acidophiles?
What is the characteristic pH range for acidophiles?
What is the term used for solutions with higher solute concentration outside the cell compared to inside?
What is the term used for solutions with higher solute concentration outside the cell compared to inside?
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Which group of microorganisms can endure very cold or even freezing temperatures?
Which group of microorganisms can endure very cold or even freezing temperatures?
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What is the preferred temperature range for psychrotrophs?
What is the preferred temperature range for psychrotrophs?
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What is the term used to describe organisms that prefer to live in salty environments?
What is the term used to describe organisms that prefer to live in salty environments?
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If a solution has the same concentration of solutes inside and outside a cell, what is it called?
If a solution has the same concentration of solutes inside and outside a cell, what is it called?
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What happens to bacteria with rigid cell walls when placed in a hypertonic solution?
What happens to bacteria with rigid cell walls when placed in a hypertonic solution?
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Which type of organism is Staphylococcus aureus classified as in terms of its preference for salty environments?
Which type of organism is Staphylococcus aureus classified as in terms of its preference for salty environments?
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What is the process known as when a bacterial cell escapes cytoplasm due to bursting in a hypotonic solution?
What is the process known as when a bacterial cell escapes cytoplasm due to bursting in a hypotonic solution?
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Which term describes microbes that can survive in high atmospheric pressure?
Which term describes microbes that can survive in high atmospheric pressure?
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What is the role of water in microbial growth?
What is the role of water in microbial growth?
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What are halophiles?
What are halophiles?
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Why can certain microbial stages like bacterial endospores survive desiccation?
Why can certain microbial stages like bacterial endospores survive desiccation?
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At what temperature do thermophiles grow best?
At what temperature do thermophiles grow best?
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What determines the temperature range over which an organism grows best?
What determines the temperature range over which an organism grows best?
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What is the optimum temperature for mesophiles to grow best?
What is the optimum temperature for mesophiles to grow best?
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Study Notes
Temperature
- Psychrophiles prefer cold temperatures, such as deep ocean water
- Psychrotrophs, a type of psychrophile, prefer refrigerator temperature (4°C)
- Psychroduric organisms can endure very cold or freezing temperatures, but prefer warm temperatures
pH
- Most microorganisms prefer a neutral or slightly alkaline growth medium (pH 7.0-7.4)
- Acidophiles prefer a pH of 2 to 5
- Alkaliphiles prefer a pH of >8.5
Osmotic Pressure and Salinity
- Osmotic pressure is the pressure exerted on a cell membrane by solutions both inside and outside the cell
- Osmosis is the movement of a solvent through a permeable membrane from a lower concentration of solutes to a higher concentration of solutes
- A hypertonic solution has a higher concentration of solutes outside the cell than inside the cell
- Plasmolysis occurs when a bacterial cell is placed in a hypertonic solution, causing the cell membrane and cytoplasm to shrink away from the cell wall
- A hypotonic solution has a lower concentration of solutes outside the cell than inside the cell
- Plasmoptysis occurs when a bacterial cell bursts in a hypotonic solution, causing the cytoplasm to escape
- Isotonic solutions have equal concentrations of solutes inside and outside the cell
- Halophilic organisms prefer to live in salty environments
- Haloduric organisms can survive in salty environments but do not prefer them
Barometric Pressure
- Piezophiles are microbes that can survive in high atmospheric pressure (>14.7 psi)
Nutrients and Moisture
- All living organisms require nutrients to sustain life
- Nutrients are energy sources, and organisms obtain energy by breaking chemical bonds
- Moisture is essential for life and necessary for carrying out normal metabolic processes
- Some microbial stages (e.g., bacterial endospores and protozoal cysts) can survive drying (desiccation)
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Description
Test your knowledge on the factors that affect microbial growth, encouraging the growth of microbes in vitro, and inhibiting the growth of microbes in vitro as outlined in Chapter 8 of Burton’s Microbiology for the Health Sciences.
