Microbiology: Chapter 7 (Nutrition, Transport, & Growth)

What are essential nutrients?

Nutrients that an organism must obtain from its environment because it cannot synthesize them in sufficient amounts.

What are organic nutrients?

Nutrients that contain carbon and hydrogen.

What are examples of organic nutrients?

• Carbohydrates

• Lipids

• Proteins

• Vitamins.

What are inorganic nutrients?

Nutrients that generally do not contain carbon-hydrogen bonds, such as minerals and water.

What are examples of inorganic nutrients?

• Water

• Salts

• Minerals such as iron, magnesium, and potassium.

What are macronutrients in microbial nutrition?

Nutrients required in relatively large amounts for cell structure and metabolism.

What are examples of macronutrients required by microorganisms?

• Carbon

• Hydrogen

• Oxygen

• Nitrogen

• Phosphorus

• Sulfur.

What are micronutrients in microbial nutrition?

Elements required in very small amounts, often to help enzymes function.

What are examples of micronutrients required by microorganisms?

• Iron

• Zinc

• Copper

• Manganese

What are the two main nutritional categories used to classify microorganisms by their carbon source?

• Autotrophs

• Heterotrophs

What is an autotroph?

An organism that uses carbon dioxide or another inorganic carbon source to make its own organic molecules

What is a heterotroph?

An organism that obtains carbon from organic compounds produced by other organisms.

What are the two main nutritional categories used to classify microorganisms by their energy source?

• Phototrophs

• Chemotrophs

What is a phototroph?

An organism that uses light as its energy source.

What is a chemotroph?

An organism that obtains energy from chemical compounds.

What is a photoautotroph?

An organism that uses light as its energy source and carbon dioxide as its main carbon source.

What is a photoheterotroph?

An organism that uses light for energy but obtains carbon from organic compounds.

What is a chemoautotroph?

An organism that obtains energy from chemical compounds and uses carbon dioxide as its main carbon source.

What is a chemoheterotroph?

An organism that obtains both energy and carbon from organic compounds.

What is a chemoorganotroph?

An organism that obtains energy by breaking down organic compounds.

If an organism degrades large organic molecules to obtain both carbon and energy, how is it best described?

A chemoorganotroph.

What is a saprobe in microbial nutrition?

An organism that obtains nutrients from dead or decaying organic matter.

How do saprobes obtain their nutrients?

They secrete enzymes that break down complex organic material outside the cell, then absorb the smaller molecules.

What is a parasite in microbial nutrition?

An organism that obtains nutrients from a living host, often harming the host.

What is the difference between a saprobe and a parasite?

A saprobe obtains nutrients from dead or decaying material, while a parasite obtains nutrients from a living host.

What is passive transport across a microbial cell membrane?

The movement of substances across the membrane without the cell using energy to drive the transport.

What is simple diffusion across a microbial cell membrane?

The movement of molecules from an area of higher concentration to an area of lower concentration without a transport protein or cellular energy.

What is osmosis in microbial cells?

The net movement of water across a selectively permeable membrane toward the area with a higher concentration of solutes.

What is facilitated diffusion across a microbial cell membrane?

The movement of substances down their concentration gradient through membrane transport proteins without cellular energy.

If glucose moves into a cell through a carrier protein down its concentration gradient, what type of transport is occurring?

Facilitated diffusion.

What is active transport across a microbial cell membrane?

The movement of substances across a membrane using cellular energy, often against their concentration gradient.

How does active transport differ from passive transport in microbial cells?

Active transport requires energy to move substances, while passive transport does not require cellular energy to drive movement.

What is group translocation in microbial transport?

A transport process in which a substance is chemically modified as it enters the cell, using energy.

What is endocytosis?

A process in which a cell membrane surrounds material and brings it into the cell in a membrane-bound vesicle.

Does endocytosis require ATP?

Yes. The cell uses energy to bring material into the cell.

What is phagocytosis?

A type of endocytosis in which a cell engulfs large particles or whole cells.

What is pinocytosis?

A type of endocytosis in which a cell takes in extracellular fluid and dissolved substances.

What environmental factors influence microbial growth?

• Temperature

• pH

• Osmotic pressure

• Water availability

• Oxygen availability

How does temperature affect microbial growth?

It affects enzyme activity and membrane function, so each microorganism has a minimum, optimum, and maximum growth temperature.

What are psychrophiles?

Microorganisms adapted to grow at cold temperatures.

What are psychrotrophs?

Microorganisms that can grow at refrigeration temperatures but generally grow best at warmer temperatures.

What are mesophiles?

Microorganisms that grow best at moderate temperatures.

What are thermophiles?

Microorganisms that grow best at high temperatures.

What are hyperthermophiles?

Microorganisms that grow best at extremely high temperatures.

Which temperature group contains most human pathogens?

Mesophiles, because human body temperature is within their favorable growth range.

How does pH affect microbial growth?

It affects enzyme function and cellular processes, and microorganisms have a preferred pH range for growth.

What are acidophiles?

Microorganisms that grow best in acidic environments.

What are neutrophiles?

Microorganisms that grow best near neutral pH.

What are alkaliphiles?

Microorganisms that grow best in alkaline environments.

How does osmotic pressure affect microbial cells?

Differences in solute concentration can cause water to move across the cell membrane, potentially damaging the cell or slowing its growth.

What happens to a microbial cell in a hypertonic environment?

Water moves out of the cell, which can cause the cytoplasm to shrink away from the cell wall in a process called plasmolysis.

What happens to a microbial cell in a hypotonic environment?

Water moves into the cell, potentially causing swelling or lysis if the cell cannot withstand the pressure.

What are halophiles?

Microorganisms that require or grow best in environments with high salt concentrations.

Why is water availability important for microbial growth?

Microorganisms need available water for biochemical reactions, nutrient transport, and cellular functions.

Why can aerobic bacteria live in an oxygen-containing environment?

They have protective enzymes, such as superoxide dismutase and catalase or peroxidase, that help neutralize toxic oxygen products.

Why can strict anaerobic bacteria be harmed by oxygen?

They lack sufficient protective enzymes to neutralize toxic oxygen products, such as superoxide radicals.

How can a hyperbaric oxygen chamber help kill anaerobic bacteria?

It exposes tissues to high oxygen levels, which can inhibit or kill susceptible anaerobic bacteria.

What are obligate aerobes?

Microorganisms that require oxygen for growth.

What are obligate anaerobes?

Microorganisms that cannot grow in the presence of oxygen because it is toxic to them.

What are facultative anaerobes?

Microorganisms that can grow with or without oxygen but generally grow better when oxygen is available.

What are aerotolerant anaerobes?

Microorganisms that do not use oxygen for metabolism but can tolerate its presence.

What are microaerophiles?

Microorganisms that require oxygen at concentrations lower than those found in the atmosphere.

What are the main types of ecological associations between microorganisms?

• Mutualism

• Commensalism

• Syntrophy

• Parasitism

• Amensalism.

What is mutualism in microbial ecology?

An association in which both organisms benefit.

What is commensalism in microbial ecology?

An association in which one organism benefits while the other is neither helped nor harmed.

What is syntrophy in microbial ecology?

A cooperative relationship in which organisms depend on each other's metabolic activities, often exchanging products that support growth.

What is parasitism in microbial ecology?

An association in which one organism benefits at the expense of its host.

What is amensalism in microbial ecology?

An association in which one organism is harmed while the other is unaffected.

What is symbiosis in microbial ecology?

A close, long-term association between organisms of different species.

What is a biofilm?

A community of microorganisms attached to a surface and embedded in a self-produced matrix.

How does a microbial biofilm typically begin to form?

Free-swimming cells attach to a surface and begin producing an adhesive matrix.

What is the function of the matrix in a microbial biofilm?

It helps hold cells together and attach them to the surface.

What is quorum sensing in microbial communities?

Cell-to-cell communication in which microorganisms release and detect signaling molecules to coordinate behavior according to population density.

How does quorum sensing help a biofilm function as a community?

When signaling molecules accumulate to a threshold level, they trigger coordinated gene expression and activities among the cells.

Why can biofilms make microbial infections harder to treat?

The biofilm matrix and coordinated community behavior can increase protection from antimicrobial agents and host defenses.

What is microbial growth at the cellular level?

The synthesis of new cell components that increases the size of an individual cell.

What is microbial growth at the population level?

An increase in the number of cells in a population through cell division.

What is binary fission in bacteria?

A form of cell division in which one parent cell divides to produce two daughter cells.

What happens first during the bacterial binary fission process?

The parent cell grows and begins replicating its chromosome.

What happens after the bacterial chromosome is replicated during binary fission?

The cell elongates and the chromosome copies separate as the cell prepares to divide.

What happens during septum formation in bacterial binary fission?

A septum forms across the cell and separates the developing daughter cells.

What happens at the end of bacterial binary fission?

The parent cell divides into two daughter cells, which can grow and divide again.

What is generation time in bacterial growth?

The time required for a bacterial population or cell to complete one doubling through cell division.

What happens during the lag phase of the bacterial population growth curve?

Cells adjust to their environment and prepare for division, so there is little or no increase in population size.

What happens during the exponential growth phase of the bacterial population growth curve?

Cells divide rapidly at a relatively constant rate, causing the population to increase exponentially.

What happens during the stationary phase of the bacterial population growth curve?

The rate of new cell production equals the rate of cell death, so the population size remains relatively stable.

What happens during the death phase of the bacterial population growth curve?

More cells die than are produced, causing the number of viable cells to decrease.

What are the four phases of the bacterial population growth curve, in order?

• Lag phase

• Exponential phase

• Stationary phase

• Death phase

Why does a bacterial population enter the stationary phase?

Nutrients become limited and waste products accumulate, reducing the rate of new cell production.

Why does a bacterial population enter the death phase?

Conditions become increasingly unfavorable, and cell death exceeds the production of new cells.

What is the relationship between binary fission and exponential population growth?

Each cell division can double the number of cells, producing exponential growth when conditions allow repeated division.

If Escherichia coli has a doubling time of 20 minutes and an experiment begins with 5 cells, how many cells will be present after 3 hours?

2,560 cells, because 3 hours contains 9 twenty-minute doubling periods and 5 × 2^9 = 2,560.

Chlamydomonas nivalis grows on Alaskan glaciers, and its photosynthetic pigments give the snow a red crust. How is this organism best described by its temperature preference?

A psychrophile.

If a cell is in a concentrated glucose solution and glucose moves into the cell through a carrier protein, what type of transport is occurring?

Facilitated diffusion.