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Questions and Answers
What type of growth occurs in the presence of oxygen?
What type of growth occurs in the presence of oxygen?
- Anaerobic growth
- Aerobic growth (correct)
- Facultative growth
- Obligate growth
Where does growth occur with respect to oxygen concentration in a tube?
Where does growth occur with respect to oxygen concentration in a tube?
- Only where low concentration of oxygen has diffused
- Best in areas where high concentration of oxygen could diffuse (correct)
- Evenly throughout the tube
- Only where there is no oxygen
What do bacteria contain to neutralize the toxic forms of oxygen?
What do bacteria contain to neutralize the toxic forms of oxygen?
- SOD only
- Neither SOD nor catalase
- Catalase only
- Both SOD and catalase (correct)
How does the pH affect bacterial growth?
How does the pH affect bacterial growth?
What type of microorganisms grow at an optimum pH well below neutral?
What type of microorganisms grow at an optimum pH well below neutral?
Which type of bacteria require oxygen for growth?
Which type of bacteria require oxygen for growth?
What is the role of SOD and catalase in bacteria?
What is the role of SOD and catalase in bacteria?
In what pH range do most bacteria grow best?
In what pH range do most bacteria grow best?
'Microorganisms that grow at an optimum pH well below Lactobacillus acidophilus' are referred to as:
'Microorganisms that grow at an optimum pH well below Lactobacillus acidophilus' are referred to as:
What type of growth occurs in the absence of oxygen?
What type of growth occurs in the absence of oxygen?
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Study Notes
Oxygen and Microbial Growth
- Growth occurs in areas where oxygen can diffuse, and is best where oxygen is present
- Some bacteria contain SOD and catalase to neutralize toxic forms of oxygen
- Others lack these enzymes, making oxygen harmful to them
- Bacteria can be classified into five groups based on their oxygen requirements:
- Obligate aerobes: require oxygen for growth
- Obligate anaerobes: cannot grow in the presence of oxygen
- Facultative anaerobes: can grow with or without oxygen
- Microaerophiles: require low levels of oxygen
- Aerotolerant anaerobes: insensitive to oxygen, live by fermentation alone
pH and Microbial Growth
- Most bacteria grow best at a pH range around neutrality (6.5-7.5)
- Fungi prefer a slightly acidic environment
- Microorganisms are classified into acidophiles, which grow at an optimum pH below neutrality
Environmental Factors Affecting Microbial Growth
- Microbial cells require suitable environmental conditions to efficiently use nutrients in metabolic reactions
- Factors affecting growth include oxygen concentration, pH, temperature, moisture and salt concentration, surface tension, and atmospheric pressure
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