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Questions and Answers
Bacteria may be divided into three groups according to their response to free molecular ______.
Bacteria may be divided into three groups according to their response to free molecular ______.
oxygen
Strict aerobes die in an ______ digester where free molecular oxygen is absent.
Strict aerobes die in an ______ digester where free molecular oxygen is absent.
anaerobic
Facultative anaerobes are active in the presence or absence of free molecular ______.
Facultative anaerobes are active in the presence or absence of free molecular ______.
oxygen
When nitrate ions are used by facultative anaerobes for degradation, ______ occurs, producing dinitrogen gas.
When nitrate ions are used by facultative anaerobes for degradation, ______ occurs, producing dinitrogen gas.
Approximately ______% of the bacteria within aerobic processes are facultative anaerobes.
Approximately ______% of the bacteria within aerobic processes are facultative anaerobes.
Anaerobes are inactive in the presence of free molecular ______.
Anaerobes are inactive in the presence of free molecular ______.
Strong acid producers among anaerobes include organisms like ______ spp.
Strong acid producers among anaerobes include organisms like ______ spp.
Oxygen-tolerant anaerobes cannot perform normal cellular activities, including the degradation of ______, in the presence of molecular oxygen.
Oxygen-tolerant anaerobes cannot perform normal cellular activities, including the degradation of ______, in the presence of molecular oxygen.
Match each group of bacteria with their characteristics:
Match each group of bacteria with their characteristics:
Match the following bacteria with their specific roles:
Match the following bacteria with their specific roles:
Match the following processes with the type of bacteria responsible:
Match the following processes with the type of bacteria responsible:
Match the following features with the correct type of bacteria:
Match the following features with the correct type of bacteria:
Match each type of anaerobic bacteria with their oxygen tolerance type:
Match each type of anaerobic bacteria with their oxygen tolerance type:
Match the following substances with the processes they participate in:
Match the following substances with the processes they participate in:
Match the following statements with their correct bacteria group:
Match the following statements with their correct bacteria group:
Match each characteristic with the correct type of metabolic activity:
Match each characteristic with the correct type of metabolic activity:
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Study Notes
Bacterial Response to Oxygen
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Strict aerobes:
- Require free molecular oxygen for survival and activity.
- Found in large numbers in aerobic processes like trickling filters and activated sludge.
- Play a significant role in waste degradation.
- Cannot survive in anaerobic environments (where free molecular oxygen is absent).
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Facultative anaerobes:
- Thrive with or without free molecular oxygen.
- Utilize free molecular oxygen for enzymatic activity and waste degradation when available.
- Can use alternative molecules like nitrate ions (NO3-) for degradation when oxygen is absent, leading to denitrification and production of dinitrogen gas (N2).
- Make up approximately 80% of bacteria in aerobic processes like fixed-film and suspended growth systems.
- Found in both aerobic and anaerobic processes.
- In anaerobic digesters, they produce acids, alcohols, carbon dioxide, and hydrogen from various waste components.
- Some species, like Escherichia coli, produce malodorous compounds like indole and skatole.
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Anaerobes:
- Inactive in the presence of free molecular oxygen.
- Divided into two subgroups: oxygen-tolerant and oxygen-intolerant (strict anaerobes).
- Oxygen-tolerant anaerobes can survive in the presence of oxygen but cannot perform normal cellular activities.
- Strict anaerobes, including methane-forming bacteria, die in the presence of oxygen.
- Some examples include:
- Streptococcus spp: strong acid producers.
- Desulfomarculum spp: reduce sulfate (SO42-) to hydrogen sulfide (H2S).
Bacteria and Oxygen
- Bacteria are divided into three groups based on their oxygen requirements: strict aerobes, facultative anaerobes, and anaerobes.
- Strict aerobes require oxygen for growth and survival. They are prevalent in aerobic wastewater treatment processes like trickling filters and activated sludge.
- Facultative anaerobes can thrive with or without oxygen. They utilize oxygen when available but can switch to alternative electron acceptors like nitrates (NO3-) when oxygen is scarce. This process is called denitrification and results in the production of nitrogen gas (N2).
- Anaerobes cannot tolerate oxygen and are divided into two subgroups: oxygen-tolerant and oxygen-intolerant (strict anaerobes).
- Oxygen-tolerant anaerobes can survive in the presence of oxygen but cannot perform cellular activities like substrate degradation.
- Oxygen-intolerant anaerobes die in the presence of oxygen. They include methane-forming bacteria crucial for anaerobic digestion.
Anaerobic Digestion
- Facultative anaerobes play a significant role in anaerobic digestion. They produce acids, alcohols, carbon dioxide, and hydrogen from carbohydrates, lipids, and proteins.
- Some facultative anaerobes, like Escherichia coli, produce malodorous compounds such as indole and skatole.
- Anaerobes, like Streptococcus spp, are strong acid producers in anaerobic environments.
- Others, such as Desulfomarculum spp, reduce sulfate (SO42-) to hydrogen sulfide (H2S).
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