Microbial Nutrition: Macronutrients and Micronutrients

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What percentage of cell dry weight is composed of a few major elements?

50%

95% (correct)

75%

99%

Which of the following macroelements is required for the activity of enzymes involved in protein synthesis?

Calcium (Ca2)

Potassium (K) (correct)

Iron (Fe2 and Fe3)

Magnesium (Mg2)

What is the primary function of magnesium in the cell?

Stabilizes ribosomes and cell membranes

Participates in electron transport chains

Serves as a cofactor for many enzymes (correct)

Contributes to heat resistance of bacterial endospores

What is the role of iron in the cell?

Serves as a cofactor for enzymes and electron-carrying proteins Signup and view all the answers

What are the four macroelements that exist in the cell as cations?

Potassium, calcium, magnesium, and iron Signup and view all the answers

What is the primary function of carbon in the cell?

Forms the skeletons or backbones of all organic molecules Signup and view all the answers

What is the primary mechanism of extinguishing a candle's flame in a candle jar?

Oxygen deprivation Signup and view all the answers

What type of microorganisms are typically grown in candle jars?

Capnophiles Signup and view all the answers

What is the purpose of inoculating the second half of the Petri dish with Serratia marcescens?

To consume oxygen Signup and view all the answers

What is the main purpose of maintaining quality control (QC) stocks in a microbiology laboratory?

To test culture media, kits, and reagents Signup and view all the answers

What is the primary reason for maintaining the purity of a microorganism in a pure culture?

To prevent contamination Signup and view all the answers

What is the purpose of sealing the Petri dish with wax or paraffin?

To prevent contamination Signup and view all the answers

What is a characteristic of obligate anaerobes?

They can live only in the absence of oxygen Signup and view all the answers

What is the primary function of extracellular electron transfer in microorganisms?

To capture or deliver electrons to donors or acceptors Signup and view all the answers

Why are anaerobes killed by oxygen?

Because they lack enzymes such as catalase, peroxidase, and superoxide dismutase Signup and view all the answers

What is the primary reason why Fe(II) is more available to microorganisms than Fe(III)?

Fe(II) is more soluble than Fe(III) at neutral pH Signup and view all the answers

What is the purpose of Fe(II) oxidizing microorganisms coupling the oxidation of iron to intracellular reduction of oxygen, carbon dioxide, and nitrate?

To avoid cell encrustation Signup and view all the answers

What is the purpose of boiling the culture medium during the preparation of Prereduced media?

To drive off most of the dissolved oxygen Signup and view all the answers

What is the function of superoxide dismutase in anaerobic bacteria?

To convert superoxide to hydrogen peroxide Signup and view all the answers

What is the essential requirement for microorganisms to grow?

Incorporation of large quantities of nitrogen, phosphorus, and sulfur Signup and view all the answers

Why are specimens from the throat or vaginal swab not submitted for anaerobic culture?

Because they are contaminated with anaerobes Signup and view all the answers

What is the result of microorganisms changing the redox state of metals?

The metals become more bioavailable Signup and view all the answers

What is the purpose of adding a reducing agent, such as cysteine, to the culture medium during the preparation of Prereduced media?

To decrease the oxygen content Signup and view all the answers

Where do microorganisms carry out the process of extracellular electron transfer?

Extracellularly, outside the cell boundaries Signup and view all the answers

At what temperature should isolates be stored for long-term preservation?

-70°C or below Signup and view all the answers

What is the recommended method for long-term preservation of bacterial culture?

Freezing at -70°C or below Signup and view all the answers

How often should non-fastidious organisms be thawed, reisolated, and refrozen when frozen at -70°C?

Every five years Signup and view all the answers

What is the purpose of adding a cryoprotectant to a solution when storing viruses at -70°C?

To protect the viruses from freezing damage Signup and view all the answers

What is the temperature of an ultralow freezer?

-70°C Signup and view all the answers

What is the term for freezing in liquid nitrogen at -196°C or in the gas phase above the liquid nitrogen at -150°C?

Cryopreservation Signup and view all the answers