Microbiology: Enzyme and Bacterial Growth Quiz

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Questions and Answers

Which nitrogen source is used for pH control in certain processes?

Sodium nitrate

Ammonium chloride

Ammonia gas (correct)

Ammonium sulfate

What is the nitrogen content in soybean meal as an organic nitrogen source?

4.5%

12%

8% (correct)

1.5%

Which of the following microorganisms has the highest carbon content?

Yeast

Fungi (correct)

Bacteria and fungi have equal carbon content

Bacteria

What effect does the use of ammonium salts have on pH when ammonia is utilized?

Produces acid conditions Signup and view all the answers

What is the function of phosphorus in the medium?

Buffer to minimize pH changes Signup and view all the answers

Which mineral element is essential in trace amounts for microbial growth?

Cobalt Signup and view all the answers

Which water treatment method is currently significant in reducing costs?

Deionization of water Signup and view all the answers

What is a common consequence of moisture, temperature, and ageing on nitrogen sources?

Changes in nitrogen availability Signup and view all the answers

What is the primary source of amino acids in plant culture media?

Casein hydrolysates Signup and view all the answers

Which of the following is classified as a growth regulator?

Auxin Signup and view all the answers

Which gelling agent is commonly used in plant culture media?

Agar Signup and view all the answers

Which vitamin is not actually considered a vitamin but is used in plant culture media?

Myo-inositol Signup and view all the answers

What is the primary action of cytokinins in plant culture?

Stimulate cell division Signup and view all the answers

What is an effect of auxin on plant growth?

Stimulates adventitious roots Signup and view all the answers

Which compound is primarily used for its ability to bind hydrophobic compounds in plant culture media?

Activated Charcoal Signup and view all the answers

Which of the following auxins acts as a herbicide by inducing unsustainable growth?

2,4-Dichlorophenoxyacetic acid Signup and view all the answers

What temperature range characterizes psychrophiles?

-5C to 15C Signup and view all the answers

Which group of bacteria can grow only in the absence of oxygen?

Obligate anaerobes Signup and view all the answers

What is the optimum growth temperature for thermophiles?

Between 45C and 70C Signup and view all the answers

Which type of bacteria tolerate oxygen but do not use it for energy?

Aerotolerant anaerobes Signup and view all the answers

What range of oxygen concentration do microaerophils require for growth?

2% to 10% Signup and view all the answers

Which type of bacteria generally grows better with oxygen?

Facultative anaerobes Signup and view all the answers

What is a characteristic of hyperthermophiles?

Thrive at temperatures between 70C and 110C Signup and view all the answers

What is the main energy acquisition method for obligate aerobes?

Aerobic respiration Signup and view all the answers

Which plant hormone is primarily responsible for preventing browning in salads?

Cytokinin Signup and view all the answers

What happens when the ratio of auxin to cytokinin is higher than 1?

Root initiation occurs Signup and view all the answers

Which plant hormone is used commercially to initiate flowering and ripen fruits such as tomatoes and bananas?

Ethylene Signup and view all the answers

What is the main purpose of using fractional factorial designs in experiments?

To assume certain interactions are negligible Signup and view all the answers

Which of the following statements is true about Plackett-Burman designs?

They focus on screening main effects efficiently Signup and view all the answers

What is a characteristic of proper fractional factorial designs?

They exhibit orthogonal properties Signup and view all the answers

Which hormone is known to regulate cell elongation and determine plant height?

Gibberellins Signup and view all the answers

Which of the following statements about abscisic acid is true?

It alters callus growth and inhibits cell division Signup and view all the answers

When are Plackett-Burman designs most beneficial?

To economically detect large main effects Signup and view all the answers

What is one purpose of Box-Behnken designs?

To determine the linear and quadratic effects of each variable Signup and view all the answers

In which scenarios should Box-Behnken designs be avoided?

When the experimenter wishes to combine factor extremes Signup and view all the answers

What is an assumption of Box-Behnken designs?

Permits complex confounding of interactions Signup and view all the answers

Which of the following is NOT a requirement for using Plackett-Burman designs?

Performing a full factorial design Signup and view all the answers

What count of runs does a Box-Behnken design require when there are 4 factors?

27 Signup and view all the answers

What characteristic is unique to Central Composite designs compared to Box-Behnken designs?

It requires a fixed number of center point runs Signup and view all the answers

What is the main focus of screening experiments discussed in the content?

To economically identify key factors Signup and view all the answers

Study Notes

### Substrate Inhibition

Substrate binds to active site of the enzyme
Inhibition increases with substrate concentration (above a threshold)

Product Inhibition

The product of the reaction (the molecule that is made) binds to the enzyme's active site
Blocks the active site and slows the reaction

Inhibition by Toxic Compound

A toxic compound binds to an enzyme and disrupts its function

### Bacterial Cell Growth

Bacteria grow in a variety of conditions
Temperature, oxygen requirements, nitrogen sources, mineral content, and water quality all impact bacterial growth

### Temperature Requirements

Bacteria can be classified based on their optimal growth temperature
Psychrophiles prefer cold temperatures (-5°C to 15°C)
Mesophiles grow best at moderate temperatures (25°C to 45°C)
Thermophiles thrive in hot temperatures (45°C to 70°C)
Hyperthermophiles grow in extremely hot conditions (70°C to 110°C)

### Oxygen Requirements

Bacteria can be classified based on their need for oxygen
Obligate aerobes require oxygen for growth
Microaerophils need low oxygen concentrations
Obligate anaerobes cannot grow in the presence of oxygen
Aerotolerant anaerobes can tolerate but do not use oxygen
Facultative anaerobes can grow with or without oxygen

Nitrogen Sources

Inorganic Nitrogen includes sources:
- Ammonia gas
- Ammonium chloride
- Ammonium sulphate
- Ammonium nitrates
- Sodium nitrates
Using ammonium salts will result in pH drift towards acidity
Using sodium nitrate results in pH drift towards alkalinity
Organic Nitrogen
- Supplied by amino acids, proteins, and urea
- Results in faster growth
- Commonly added as complex sources like:
  - Soybean meal
  - Corn steep liquor

### Water Quality

Assessing Water Suitability:
- Check pH level
- Measure dissolved salts
- Assess effluent contamination
In Older Practices water mineral content was important
- High calcium levels were important for making dark beer
- High carbonate levels were important for making stouts.
Modern Practices:
- Deionization of water is common
- Reuse of water can reduce water cost and effluent treatment expenses

### Elemental Composition of Bacteria

Carbon (C) (50-53%) Key component of organic molecules
Hydrogen (H) (7%) Vital for water, organic molecules, and energy production
Nitrogen (N) (12-15%) Important for proteins, nucleic acids, and vitamins
Phosphorus (P) (2-3%) Essential for DNA, RNA, ATP, and cell membranes
Sulphur (S) (0.2-1.0%) Found in amino acids, vitamins, and enzymes
Potassium (K) (1.0-4.5%) Important for enzyme function, carbohydrate metabolism, and osmotic balance
Sodium (Na) (0.5-1.0%) Necessary for cell transport and osmotic balance
Calcium (Ca) (0.01-1.1%) Found in cell walls and involved in various cellular processes
Magnesium (Mg) (0.1-0.5%) Important for enzyme function and chlorophyll production
Chloride (Cl) (0.5%) Involved in osmotic balance
Iron (Fe) (0.02-0.2%) Crucial for electron transport in respiration

### Mineral Sources

Microorganisms need minerals for growth, metabolism, and product formation
Essential Minerals:
- Magnesium
- Phosphorus
- Potassium
- Sulphur
- Calcium
- Chlorine
Trace Minerals:
- Cobalt
- Copper
- Manganese
- Iron
- Molybdenum
- Zinc

### Carbon Sources

Carbon is used to metabolise ATP and other energy molecules
Commonly Used:
- Glucose
- Sucrose
- Galactose
- Sorbitol
- Maltose

### Organic Supplements

Amino Acids
- Provide nitrogen and support metabolism and biosynthesis of proteins, lipids, and nucleotides
- Typical source is casine (milk protein) hydrolysates
Vitamins
- Important for metabolic processes
- Vitamin B1 (thiamin)
- Vitamin B6 (nicotinic acid pyridoxine)
- Myo-inositol (not a vitamin but used for plant culture media)
Activated Charcoal (AC)
- Binds hydrophobic compounds that can inhibit growth
- Used for detoxification
Gelling Agents (Support Systems)
- Solidified surface typically made from complex carbohydrates extracted from seaweed (agar)
- Provides structure for microbial growth
- Alternatives:
  - Gums from plants
  - Agarose

### Plant Culture Media

Growth Regulators:
- Auxin
- Cytokinin
- Gibberellins
- Abscisic acid
- Ethylene

### Auxin

Promotes cell division and growth
Most auxins are synthetic
Naturally produced 1H-indol-3-acetic acid (unstable to heat and light)
Produced in apical and root meristems, seeds, and developing fruit
Alters target cell proton pumps and ATP production
Induces cell elongation
Suppresses lateral bud growth
Stimulates adventitious roots
Example: 2-4-dichorophenoxyacetic acid (2-4D) - used as a herbicide

### Cytokinins

Promote cell division
Produced in young leaves, fruits, and seeds
Stimulate cell division
Induce shoot formation
Promote axillary shoot proliferation
Inhibit root formation
Delays cell aging
Increases fruit blooming and growth
Can increase fruit size when mixed with gibberellins
Ratio of Auxin and cytokinin control root formation
- More auxin than cytokinin: promotes root growth
- More cytokinin than auxin: promotes shoot growth

### Gibberellins & Abscisic Acid

Regulate cell elongation and determine plant height
Gibberellins
- Increase growth of low-density cultures
- Enhance callus growth
- Elongate dwarf plants
Abscisic Acid
- Alters callus growth
- Enhances bud and shoot formation
- Inhibits cell division
- Commonly used in somatic embryogenesis

### Ethylene

Volatile gas produced during ripening, stress, mechanical damage, or infection
Produced from methyl group of methionine
Almost all plant tissues produce ethylene
Induces fruit ripening and flower blooming
Commercially used to initiate flowering and ripen tomatoes, citrus, and bananas
Specific protein receptors for ethylene act as transcription factors
Can be a problem in culture without proper air circulation

### Design of Experiments

Focus on identifying the most important factors that impact a process
Experiment types:
- Fractional Factorial Designs
- Plackett-Burman
- Box-Behnken

### Fractional Factorial Designs

Help study multiple factors (k) in a limited number of runs (N)
Assume high-order interactions are negligible
Desirable properties:
- Balanced (same number of observations in each run)
- Orthogonal (effects of factors sum to zero across other factors)

### Plackett-Burman Designs

Fractional factorial designs used to study k = N – 1 variables in N runs (where N is a multiple of 4)
Focus on main effects only
Standard orthogonal arrays
No defining relation since interactions are not equal to main effects
No degrees of freedom for calculating error term

When to Use Plackett-Burman Designs

Screening experiments
When higher-order interactions are negligible
To efficiently identify large main effects

### Box-Behnken Designs

Three-level multi-factor experiments
Combine two-level factorial designs with incomplete block designs
Complex confounding of interactions
Efficient for detecting large main effects
Can test linear and quadratic (non-linear) effects for each factor
Rotatable

When to Use Box-Behnken Designs

Three-level multi-factor experiments
To detect large main effects when resources are limited
To determine linear and quadratic effects of variables
To avoid extreme factor combinations

### Number of Runs Required for Central Composite and Box-Behnken Designs:

As the number of factors increases, the required number of runs increases

Number of Factors	Box-Behnken Runs	Central Composite Runs
2	-	13 (5 center points)
3	15	20 (6 center point runs)
4	27	30 (6 center point runs)
5	46	33 (fractional factorial) or 52 (full factorial)
6	54	54 (fractional factorial) or 91 (full factorial)

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Description

Test your knowledge on enzyme inhibition and factors affecting bacterial growth. This quiz covers substrate inhibition, product inhibition, and the conditions necessary for bacterial growth, including temperature and oxygen requirements. Dive into the fascinating world of microbiology and assess your understanding!