Microbial Growth Nutritional Requirements

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Questions and Answers

What percentage of the dry weight of a typical bacterial cell is made up of carbon?

50% (correct)

70%

25%

10%

Which of the following is a common source of phosphorus for microorganisms?

Ammonium ions (NH4+)

Phosphate ion (PO43-) (correct)

Carbon dioxide

Hydrogen sulfide

Which group of bacteria is known for directly using gaseous nitrogen from the atmosphere?

Nitrogen-fixing bacteria (correct)

Photoautotrophs

Chemoheterotrophs

Chemoautotrophs

Which minerals are commonly needed by microorganisms as cofactors for enzyme functions?

Iron, copper, molybdenum, and zinc Signup and view all the answers

Which of the following best describes chemoheterotrophs?

They use organic chemicals as a source of energy and carbon. Signup and view all the answers

What is the role of nitrogen in microbial cellular material synthesis?

It is essential for protein and nucleic acid synthesis. Signup and view all the answers

Which process allows some bacteria to utilize nitrogen directly from the atmosphere?

Nitrogen fixation Signup and view all the answers

What allows facultative anaerobes to grow in the absence of oxygen?

They use fermentation or anaerobic respiration. Signup and view all the answers

What element constitutes about 14% of the dry weight of a bacterial cell?

Nitrogen Signup and view all the answers

What is the role of superoxide dismutase (SOD) in aerobic organisms?

To neutralize toxic superoxide radicals. Signup and view all the answers

Which enzyme breaks down hydrogen peroxide into water and oxygen?

Catalase Signup and view all the answers

Which of the following statements about obligate aerobes is true?

They are more efficient in energy extraction compared to anaerobes. Signup and view all the answers

Obligate anaerobes are most affected by oxygen because:

Oxygen causes the production of toxic superoxide radicals. Signup and view all the answers

What is the most reactive intermediate form of oxygen, known for causing cellular damage?

Hydroxyl radicals Signup and view all the answers

Which type of bacteria is capable of deriving energy from both aerobic and anaerobic processes?

Facultative anaerobes Signup and view all the answers

Which statement is true about hydrogen peroxide in biological systems?

It is produced as a waste product during aerobic respiration. Signup and view all the answers

Study Notes

Chemical Requirements for Microbial Growth

Carbon is the backbone of all organic compounds in living cells.
- Chemoheterotrophs obtain carbon from organic molecules like carbohydrates, proteins, and lipids, which also serve as their energy source.
- Chemoautotrophs and photoautotrophs obtain carbon from carbon dioxide (CO2).
Nitrogen, Sulfur, & Phosphorus are also essential for microbial growth.
- Nitrogen is crucial for protein synthesis and makes up 14% of a bacterial cell's dry weight.
- Sulfur is needed for some protein synthesis and is obtained from sources like sulfate ions (SO42-), hydrogen sulfide, and sulfur-containing amino acids.
- Phosphorus is essential for DNA and RNA synthesis and is primarily obtained as phosphate ions (PO43-).
Trace Elements are minerals in small amounts, such as iron, copper, molybdenum, and zinc, essential for enzyme functions as cofactors.
Oxygen is essential for energy extraction by aerobes, but it's poorly soluble in water.
- Obligate aerobes require oxygen to live.
- Facultative anaerobes can use oxygen when present but can also grow through fermentation or anaerobic respiration in its absence.
- Obligate anaerobes cannot use oxygen for energy and are often harmed by its presence.
Toxic Forms of Oxygen can harm or kill microbes:
- Singlet oxygen (1O2-) is a highly reactive form of oxygen.
- Superoxide radicals (O2-) are naturally produced during aerobic respiration.
- Hydrogen peroxide (H2O2) is also toxic and is found in antimicrobials.
- Hydroxyl radicals (OH·) are the most reactive form of oxygen and are produced by ionizing radiation.

Enzymes for Oxygen Tolerance

Superoxide dismutase (SOD) neutralizes superoxide radicals.
Catalase converts hydrogen peroxide into water and oxygen.
Peroxidase breaks down hydrogen peroxide without producing oxygen.

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Description

Explore the chemical requirements essential for microbial growth in this quiz. Learn about the roles of carbon, nitrogen, sulfur, phosphorus, trace elements, and oxygen. Test your understanding of how these elements contribute to the life processes of different types of microorganisms.