Microbiology: Growth Factors Overview

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Questions and Answers

What are growth factors primarily composed of?

Minerals and proteins

Nucleotides and fats

Organic compounds (correct)

Lipids and carbohydrates

Which of the following is NOT considered a major class of growth factors?

Steroids (correct)

Amino acids

Vitamins

Purine and pyrimidines

Which microorganism is known for manufacturing Vitamin D through industrial fermentation?

Saccharomyces (correct)

Bacillus subtilis

Staphylococcus aureus

Escherichia coli

What is the purpose of a growth-response assay?

To detect the specific growth factor needed by microbes Signup and view all the answers

Which of the following best describes growth factors?

They cannot be synthesized by some organisms and must be obtained from the environment. Signup and view all the answers

Which ingredient is found in the BM+G chemically defined medium?

(NH4)2SO4 Signup and view all the answers

What characterizes chemically defined media?

Exact chemical composition is known and measured amounts are used. Signup and view all the answers

What is a defining feature of complex media?

Components can vary from batch to batch. Signup and view all the answers

Which of the following is an ingredient in Luria Bertani (LB) medium?

Tryptone Signup and view all the answers

What role does solidified media play in microbiology?

It helps in the identification of microorganisms through colony morphology. Signup and view all the answers

What percentage concentration of agar is most commonly used as a solidifying agent?

1.5% Signup and view all the answers

Which component of Tryptic Soy Broth (TSB) serves as a source of protein?

Tryptone Signup and view all the answers

Which of the following statements is true regarding chemically undefined media?

They contain components of unknown composition. Signup and view all the answers

What is the main advantage of using a chemostat over a batch culture?

It allows for the control of growth rate and population density independently. Signup and view all the answers

In what phase of the bacterial growth curve do cells primarily adjust their metabolism and prepare for growth?

Lag Phase Signup and view all the answers

Which of the following best describes the Exponential Phase of bacterial growth?

Cells grow and divide at the maximum possible growth rate. Signup and view all the answers

How does a chemostat allow for the study of microbial growth?

By allowing control over nutrient availability and dilution rates. Signup and view all the answers

What is the outcome when unbalanced growth occurs?

Cells synthesize cellular constituents at changed relative rates. Signup and view all the answers

What is an essential characteristic of the cells during the Exponential Phase?

All components are synthesized at constant rates relative to one another. Signup and view all the answers

What happens during the Lag Phase concerning cell numbers?

There is no significant increase in cell numbers despite growth. Signup and view all the answers

Why is exponential growth considered balanced growth?

Because all components are made at constant rates relative to each other. Signup and view all the answers

What defines the minimum temperature for microbial growth?

It is the temperature below which cells become inactive. Signup and view all the answers

Which group of microbes can grow optimally at temperatures as low as 15°C?

Psychrophiles Signup and view all the answers

What is the significance of agar in microbial culture?

It melts at 90°C and solidifies at 45°C. Signup and view all the answers

What is the maximum temperature threshold for mesophiles?

45°C Signup and view all the answers

Which adaptations are common in psychrophilic enzymes?

Greater amounts of polar amino acids. Signup and view all the answers

What type of media is tryptic soy broth classified as?

Complex media Signup and view all the answers

What is the primary reason for the growth cessation above maximum temperature?

Inactivation of key proteins. Signup and view all the answers

Which of the following is an example of a selective medium?

Mannitol salt agar Signup and view all the answers

What describes an enriched medium?

It mimics natural conditions by adding components like whole blood. Signup and view all the answers

Which statement correctly describes psychrotolerant microbes?

They can grow at 0°C but prefer higher temperatures. Signup and view all the answers

What temperature range is typically spanned by the growth temperatures of specific organisms?

30 to 40°C Signup and view all the answers

What does a differential medium contain?

Substances for distinguishing metabolic activities. Signup and view all the answers

Pyrolobus fumarii is an extremophile known for its maximum growth temperature. What is this temperature?

113°C Signup and view all the answers

What is the primary goal of the enrichment technique developed by Beijerinck?

To favour the growth of a specific group of microorganisms. Signup and view all the answers

Why might not all microbes be cultured in the laboratory?

They may lack the necessary nutrients found in media. Signup and view all the answers

What term describes media that combine selective and differential characteristics?

Selective differential media Signup and view all the answers

Study Notes

Growth Factors

Some microorganisms rely on external sources for essential components due to lacking specific enzymes.
Growth factors are organic compounds vital for cellular functions that cannot be synthesized by certain organisms.
Major classes of growth factors include:
- Amino acids
- Purines and pyrimidines
- Vitamins such as thiamine, biotin, cobalamin, and pyridoxine.
Other growth factors include heme (present in cytochromes) and cholesterol.
Understanding growth factor needs aids in:
- Conducting bioassays to identify specific microbial growth factors.
- Utilizing growth-response assays that are specific, sensitive, and quantitative.
- Industrial production of growth factors (example: vitamin D by Saccharomyces).

Physical Factors Influencing Growth

Temperature impacts microbial growth; cardinal temperatures include:
- Minimum temperature: below which cell activity halts.
- Optimum temperature: the highest growth rate occurs, close to maximum.
- Maximum temperature: above which growth ceases due to protein inactivation or membrane disruption.
Cardinal temperatures differ among organisms and can range from 0°C to 75°C, with some capable of surviving up to 113°C (e.g., Pyrolobus fumarii).
Microbes can be categorized based on temperature optima:
- Psychrophiles: thrive at 0°C - max at ~20°C.
- Psychrotolerant: grow well at 0°C; optimal at 20°C - 30°C.
- Mesophiles: optimal temperatures of 25°C - 40°C; common microbes.

Culture Media Types

Chemically Defined Media:
- Exact chemical composition is known; used for controlled experiments.
- Example: BM+G medium with defined amounts of glucose, salts, and amino acids.
Complex Media:
- Composition varies between batches, less control over nutrient composition.
- Example: Luria Bertani (LB) and Tryptic Soy Broth (TSB) used for general growth needs.

Media Consistency and Application

Media can be liquid or solidified, essential for pure culture establishment and cell enumeration.
Solidifying agent: agar, extracted from red algae, melts at 90°C, solidifies at 45°C, resistant to microbial hydrolysis.
Types of culture media:
- General-purpose (supportive) media sustain a variety of microbes.
- Enriched media contains additional nutrients for fastidious organisms.
- Selective media favor certain microbes while inhibiting others.
- Differential media allow for distinguishing metabolic activities.

Enrichment Technique

Developed by Beijerinck to promote the growth of specific microbial groups over others in a mixed sample.

Notes on Culturing Microbes

Not all microbes are cultivable in the lab; selective conditions may be needed to foster particular groups.
Chemostat allows control of growth rate and density independently, differing from batch cultures.
- Can maintain populations in exponential phase and study growth under low nutrient conditions.

Bacterial Growth Curve

Monitored growth of batch cultures can be represented as a growth curve divided into four phases:
- Lag Phase: cells adapt and prepare for growth; no increase in count.
- Exponential Phase (Log phase): maximum growth rate occurs; cells divide rapidly; uniform properties.
  - Balanced growth: proportionate synthesis of cellular components.
  - Unbalanced growth results from nutrient/environmental changes.

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Description

Explore the essential growth factors required by microbes, including amino acids, purines, pyrimidines, and vitamins. This quiz covers the major classes of growth factors that microbes cannot synthesize and must obtain from their environment. Understand the role of these organic compounds in cellular function.