[01.17] General Concepts in Microbiology 2 V2

Increase in population, not cell size

What is measured as microbial growth?

Increase in cell number or overall mass

How can microbial growth be measured?

Infection control and growth of industrial and biotech organisms

What are two important applications for controlling microbial growth?

Asexual reproduction

What type of reproduction do bacteria and archaea exclusively engage in?

Binary Fission

What is the most common form of reproduction for bacteria?

A single cell splits into two equally sized cells

Describe the fundamental process of binary fission.

Budding, Conidiospores (filamentous bacteria) or spore formation, Fragmentation

Name three alternative methods of bacterial reproduction.

Cell elongation

What is the initial step in the binary fission process?

Careful enlargement of the cell membrane and cell wall, and an increase in cell volume

What two things are required for cell elongation during binary fission?

DNA replication

What cellular process occurs in preparation for chromosome copying during binary fission?

Septum

What protein is essential for the formation of a ring in the middle of an elongated cell during binary fission?

After the nucleoids are segregated to each end of the elongated cell

When is septum formation completed during binary fission?

Two equally sized daughter cells

What is the final result of one round of binary fission?

20 minutes

How quickly can the entire cell cycle take for an active culture of Escherichia coli?

Generation time or doubling time

What is the term for the time required for a cell to divide or for a population to double?

1-3 hours

What is the average generation time for bacteria?

20 minutes

What is the doubling time for E. coli under ideal conditions?

1 million cells

How many cells can one cell become after 20 generations, which takes approximately 7 hours?

Exponentially or logarithmically with base 2

How does a unicellular bacterial population increase?

X * 2^n

What is the formula for calculating bacterial population, where X is the initial number of bacterial cells and n is the number of generations?

Lag Phase, Exponential Growth Phase, Stationary Phase, Death Phase

What are the four distinct growth phases observed when an organism is inoculated into a nutrient solution?

Lag Phase

In which growth phase do organisms adjust to the medium and induce necessary enzymes, leading to delayed cell division?

Logarithmic/Exponential Growth Phase

In which growth phase is generation time measured, and bacteria divide as fast as soluble nutrients permit?

Logarithmic/Exponential Growth Phase

During which growth phase are bacteria most sensitive to drugs and radiation?

Stationary Phase

In which growth phase is the number of new cells equal to the number of dead cells, resulting in no net increase in viable cells?

Nutrients becoming limiting, toxic waste buildup, oxygen depletion, cessation of an essential nutrient, or pH changes due to end products

List five conditions that can cause a bacterial culture to enter the stationary phase.

Death Rate = Cell Division Rate

What relationship between cell death and division rates characterizes the stationary phase?

Death Phase

In which growth phase does the rate of cell death exceed the rate of regeneration, potentially accelerating exponentially?

Some toxic substance excreted from the bacteria

What is a primary cause of the death phase in bacterial growth?

Temperature, pH, and osmotic pressure

What are the three main physical requirements that affect bacterial growth?

Minimum growth temperature, Optimum growth temperature, Maximum growth temperature

What are the three cardinal temperature points for microbial growth?

Optimum growth temperature

What temperature is usually near the top of the growth range and represents where the best growth occurs?

Enzyme inactivation

What causes the death of bacteria above their maximum growth temperature?

Mesophiles

Which is the most common group of organisms, typically found in the 20°C to 40°C temperature range?

It slows or stops the growth of most microbes

What effect does a temperature of 40°F (5°C) have on the growth of most microbes?

Psychrophiles, Mesophiles, Thermophiles, Hyperthermophiles

How are microorganisms classified based on their temperature preferences?

0 to 20°C

What is the temperature range for psychrophiles?

20°C to 40°C

What is the temperature range for mesophiles?

Higher than 40°C

What is the temperature range for thermophiles?

Beyond 70°C

What is the temperature range for hyperthermophiles?

15°C

What is the optimal growth temperature for psychrophiles?

0°C

What is the minimal growth temperature for psychrophiles?

20°C

What is the maximal growth temperature for psychrophiles?

Psychrotrophs

What are cold-tolerant bacteria that can grow at low temperatures but have optimal growth temperatures greater than 15°C?

Enduring extended periods of cryobiosis

What are psychrophiles and psychrotrophs often capable of enduring in cold ecosystems?

pH

What term describes the extent of acidity or alkalinity of a solution?

6.5 and 7.5

What pH range do most bacteria grow within?

7.0 - 7.2

What is the typical pH range of most humans?

Neutrophilic bacteria

What type of bacteria typically grows well in the human body's pH range?

It limits bacterial growth

Why is an acidic environment (below pH 4) good for preserving foods like pickles and sauerkraut?

Acidophiles

What type of organisms can live at low pH, such as those found in yogurt, or most molds and yeasts?

Osmotic pressure

What physical condition needs to be ideal for microbial growth to proceed best?

Plasmolysis

What can occur in hypertonic environments, where increased salt or sugar causes water to flow out of the cell?

Extreme or obligate halophiles

Which organisms require high osmotic pressure for growth?

Facultative halophiles

Which organisms can tolerate high osmotic pressure but do not require it?

About 1%

What is the normal salt concentration of microbial cytoplasm?

Water will flow out, causing the microorganisms to shrink and die

What happens to a microorganism if the external salt concentration increases significantly?

It will flow through the cell membrane and into the cytoplasm, causing the cell to swell and burst

What happens to a microorganism if external water is free of salt?

Water, Mineral elements, Growth factors, Gas (e.g., oxygen)

What four categories of chemical substances must microorganisms have a supply of to grow successfully?

Carbon

What element makes up 50% of a bacterium's dry weight and serves as a structural organic molecule and energy source?

Organic materials in the environment or derived from carbon dioxide

From what two sources can bacteria obtain carbon?

Chemoautotrophs

Which organisms use chemical reactions to obtain their energy and nutrients from simple inorganic compounds like carbon dioxide?

Photoautotrophs

Which organisms use photosynthesis to obtain their energy and nutrients from simple inorganic compounds like carbon dioxide?

Chemoheterotrophs

Which organisms use organic carbon sources?

Nitrogen

What element is found in amino acids and proteins, and is essential for the synthesis of amino acids, proteins, DNA, and RNA?

Proteins

What do most bacteria decompose to obtain nitrogen?

Ammonium (NH4+) or nitrate (NO3-)

What inorganic forms of nitrogen can some bacteria use?

Nitrogen-fixing bacteria

What type of bacteria obtains nitrogen directly from the atmosphere (N2)?

Phosphorus

What element is needed for nucleic acid synthesis and the construction of phospholipids, and is found in DNA, RNA, ATP, and membranes?

Phosphate (PO4^3-)

What is a common source of phosphorus?

Sulfur

What element is found in amino acids such as thiamine and biotin?

Proteins

What do most bacteria decompose to obtain sulfur?

Sulfate (SO4^2-) or hydrogen sulfide (H2S)

What inorganic forms of sulfur can some bacteria use?

Oxygen

What gas is used by aerobic bacteria during cellular respiration as the final electron acceptor?

Obligate Aerobes

Which type of bacteria absolutely requires oxygen for energy yielding properties and growth?

Anaerobes

What is the general term for microorganisms that grow in an oxygen-free environment and often produce odoriferous gases?

Clostridium species

Name a pathogenic species that is anaerobic.

Facultative anaerobes

Which organisms can use oxygen but are also capable of growing without it?

Obligate anaerobes

Which organisms do not need oxygen for growth and die in its presence because it is toxic to them?

Aerotolerant anaerobes

Which organisms are generally anaerobic but can tolerate exposure to oxygen?

Microaerophiles

Which organisms require or prefer reduced amounts of oxygen levels for growth?

Inorganic elements required in small amounts, usually as enzyme cofactors

What are trace elements for bacteria?

Iron, copper, and zinc

Name three examples of trace elements.

Vitamins, amino acids, purines, and pyrimidines

Name four types of organic compounds that some bacteria require from the environment.

Endospores

What is an example of an extreme survival strategy employed by certain gram-positive bacteria when favored nutrients are exhausted?

Nutrient deprivation

What usually initiates the formation of endospores?

Bacillus, Clostridiums, and G+ genera

Name three types of gram-positive bacteria that are known to form endospores.

To produce a dormant and highly resistant cell to preserve the cell’s genetic material in times of extreme stress

What is the primary purpose of endospore formation?

Long periods of drought

What harsh environmental condition can endospores survive for extended periods?

Culture media

What is the term for a food, gel, or liquid designed to support the growth and control of microbes?

Nutrient broth and agar plates

What are the two most common types of growth media?

Fastidious organisms

What term describes organisms that require specialized environments due to their complex nutritional requirements?

Liquid form

What is the physical form of nutrient broth?

Agar

What is a complex polysaccharide that serves as a solidifying agent for culture media?

It is generally not metabolized by microbes

Why does agar remain solid when used as a culture medium?

100°C

At what temperature does agar liquefy?

~40°C

At what temperature does agar solidify?

Defined Media

Which type of media has known quantities of all ingredients, including defined carbon and nitrogen sources?

Glucose or glycerol

What are two common carbon sources used in defined media?

Ammonium salts or nitrates

What are two common inorganic nitrogen sources used in defined media?