21 Questions
Which element is required for the activity of several enzymes?
Potassium
What are growth factors?
Organic micronutrients required for growth
Which type of media is considered 'simple' because it contains only a single carbon source?
Defined media
What is the disadvantage of using a complex medium for culturing microorganisms?
Its nutritional composition is not known precisely
What is the purpose of a selective medium in diagnostic microbiology?
To inhibit the growth of certain microorganisms
Which organism listed in Table 3.2 has the greatest biosynthetic capacity?
Thiobacillus thioparus
Which elements are considered essential for microbial life?
Hydrogen, oxygen, carbon, nitrogen, phosphorus, sulfur, and selenium
What is the chemical makeup of a microbial cell primarily composed of?
Macromolecules
What is the percentage of proteins in the total cell dry weight?
55%
Which element is required for the activity of several enzymes?
Potassium
What is the main role of iron in cellular respiration?
To stabilize ribosomes, membranes, and nucleic acids
What is the disadvantage of using a complex medium for culturing microorganisms?
It promotes the growth of unwanted contaminants
What is a common indication of a contaminated culture?
Presence of foul odor
What is the purpose of agar in solid culture media?
To immobilize cells and allow them to grow
Which organism listed in Table 3.2 has the most demanding nutritional requirements?
T. thioparus
What is the purpose of aseptic technique in microbiology?
To prevent contamination during manipulations
What is the main method for obtaining pure cultures from liquid samples containing several different organisms?
Restreaking an isolated colony
Which of the following is NOT a type of culture medium used in microbiology?
Selective media
Which of the following is true about growth factors?
They are organic micronutrients
Which of the following is an advantage of using a complex medium?
It supports growth of fastidious microorganisms
Which of the following is a characteristic of selective media?
They contain compounds that inhibit the growth of all microorganisms
Study Notes
Enzymes and Essential Elements
- Iron is required for the activity of several enzymes.
- Iron plays a crucial role in cellular respiration.
Microbial Growth and Media
- Simple media contain a single carbon source.
- Complex media have a disadvantage, as they can support the growth of contaminants, making it difficult to isolate the desired microorganism.
- Selective media are used in diagnostic microbiology to isolate specific microorganisms.
- Agar is used in solid culture media to provide a solid surface for microorganisms to grow.
Microbial Composition
- Microbial cells are primarily composed of carbon, oxygen, nitrogen, and hydrogen.
- Proteins make up approximately 50% of the total cell dry weight.
Microorganisms and Nutritional Requirements
- The organism with the greatest biosynthetic capacity is Escherichia coli (E. coli).
- The organism with the most demanding nutritional requirements is Lactobacillus acidophilus.
Aseptic Technique and Culture Methods
- Aseptic technique is used in microbiology to prevent contamination of cultures.
- The main method for obtaining pure cultures from liquid samples containing several different organisms is through the use of selective media and aseptic technique.
Culture Media and Characteristics
- Defined media, complex media, and selective media are types of culture media used in microbiology.
- Growth factors are organic compounds required by some microorganisms for growth.
- A characteristic of selective media is that they allow only specific microorganisms to grow.
Test your knowledge on culture media and carbon sources used for culturing microorganisms. Learn about different recipes for culture media and understand the role of carbon sources in microbial growth.
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