Microbiology Chapter 06: Microbial Nutrition and Growth

This set of vocabulary flashcards covers essential nutrients, environmental growth factors, metabolic classifications, transport mechanisms, and population growth dynamics in microbiology.

Essential nutrient

Any substance that must be provided to an organism.

Macronutrients

Nutrients required in relatively large quantities that play principal roles in cell structure and metabolism, such as carbon, hydrogen, and oxygen.

Micronutrients

Also known as trace elements; substances like manganese, zinc, and nickel that are required in small amounts for enzyme function and protein structure maintenance.

Inorganic nutrient

An atom or simple molecule that contains a combination of atoms other than carbon and hydrogen, often found in the earth's crust or atmosphere.

Organic nutrients

Molecules containing carbon and hydrogen atoms that are products of living things, ranging from simple methane to large polymers like carbohydrates and proteins.

Heterotroph

An organism that must obtain its carbon in an organic form.

Autotroph

An organism that uses inorganic $CO_2$ as its carbon source and is not nutritionally dependent on other living things.

Phototroph

Microbes that gain energy from visible light rays via photosynthesis.

Chemotroph

Microbes that gain energy from chemical compounds.

Photoautotrophs

Photosynthetic organisms that produce organic molecules using $CO_2$ to be used by themselves and heterotrophs.

Chemoorganic autotrophs

Organisms that use organic compounds for energy and inorganic compounds as a carbon source.

Lithoautotrophs

Organisms that rely totally on inorganic minerals for energy and carbon, requiring neither sunlight nor organic nutrients.

Chemoheterotrophs

Organisms that derive both carbon and energy from organic compounds via respiration or fermentation.

Saprobes

Free-living decomposers that feed on organic detritus from dead organisms to recycle organic nutrients.

Parasites

Organisms that derive nutrients from the cells or tissues of a living host.

Pathogens

Parasites that cause damage to tissues or death in their hosts.

Obligate parasites

Parasites that are unable to grow outside of a living host, such as the leprosy bacillus.

Diffusion

The movement of atoms or molecules in a gradient from an area of higher density or concentration to an area of lower density or concentration.

Osmosis

The diffusion of water through a selectively, or differentially, permeable membrane.

Isotonic

A condition where water concentration is equal inside and outside the cell, resulting in equal rates of diffusion in both directions.

Hypotonic

A solution where the net diffusion of water is into the cell; in cells without walls, this may cause bursting.

Hypertonic

A solution where water diffuses out of the cell, causing the cell to shrink.

Plasmolysis

The process in a hypertonic solution where the cytoplasmic membrane pulls away from the cell wall as the cell shrinks.

Endocytosis

A transport process where a cell encloses a substance in its membrane and forms a vacuole to engulf it.

Phagocytosis

A type of endocytosis used by amoebas and white blood cells to ingest whole cells or large solid matter.

Pinocytosis

The ingestion of liquids, such as oils or molecules in solution, by the cell.

Cardinal temperatures

The range of temperatures (minimum, maximum, and optimum) for the growth of a specific microbial species.

Minimum temperature

The lowest temperature that permits a microbe’s continued growth and metabolism.

Maximum temperature

The highest temperature at which growth and metabolism can proceed before proteins are denatured.

Optimum temperature

The temperature that promotes the fastest rate of growth and metabolism.

Psychrophiles

Organisms with an optimum temperature below $15^{\circ}\text{C}$ that are capable of growth at $0^{\circ}\text{C}$.

Psychrotrophs

Organisms that grow slowly in the cold but have an optimum temperature between $15^{\circ}\text{C}$ and $30^{\circ}\text{C}$; examples include Staphylococcus aureus and Listeria monocytogenes.

Mesophiles

The majority of medically significant microorganisms that grow at intermediate temperatures between $20^{\circ}\text{C}$ and $40^{\circ}\text{C}$.

Thermoduric

Organisms that are normally mesophiles but can survive short exposure to high temperatures, often contaminating pasteurized foods.

Thermophile

An organism that grows optimally at temperatures greater than $45^{\circ}\text{C}$, often found in volcanic activity or compost piles.

Extreme thermophiles

Organisms that grow between $80^{\circ}\text{C}$ and $121^{\circ}\text{C}$.

Superoxide dismutase

The enzyme that converts the toxic superoxide ion ($O_2^-$) into hydrogen peroxide ($H_2O_2$).

Catalase

The enzyme that converts toxic hydrogen peroxide ($H_2O_2$) into harmless water and oxygen.

Obligate aerobe

An organism that cannot grow without oxygen.

Microaerophiles

Organisms that do not grow at normal atmospheric oxygen levels but require a small amount for metabolism.

Facultative anaerobes

Organisms that do not require oxygen for metabolism but use it when present and can also perform anaerobic metabolism.

Obligate anaerobes

Organisms that lack the enzymes for processing toxic oxygen and die in its presence.

Aerotolerant anaerobes

Organisms that do not utilize oxygen but can survive and grow to a limited extent in its presence.

Capnophiles

Organisms that grow best at higher $CO_2$ tensions than normally present in the atmosphere, such as Neisseria.

Acidophiles

Organisms that thrive in acidic environments, such as Euglena mutabilis which grows between pH $0$ and $1$.

Alkalinophiles

Organisms that thrive in alkaline conditions, such as Natromonas (pH $12$).

Osmophiles

Organisms that live in habitats with high solute concentration.

Halophiles

Microbes that prefer high concentrations of salt.

Barophiles

Bacteria adapted to high pressures (up to $1,000$ times atmospheric pressure) that will rupture at normal pressure.

Symbiosis

A general term for a situation in which two organisms live together in a close partnership.

Mutualism

A symbiotic relationship that is obligatory and mutually beneficial to both organisms.

Commensalism

A relationship where the commensal receives benefits while the partner is neither harmed nor benefitted.

Parasitism

A relationship where the host provides the microbe with nutrients and a habitat, usually resulting in harm to the host.

Antagonism

An association between free-living species where members compete for space and nutrients, often through antibiosis.

Synergism

An interrelationship between two organisms that benefits them but is not necessary for survival; they cooperate to produce results neither could achieve alone.

Biofilms

Mixed communities of bacteria and other microbes attached to a surface and each other, such as those found on gauze fibers.

Quorum sensing

The release of chemicals by bacteria to interact with members of the same or other species and monitor population density.

Binary fission

The process by which one bacterial cell duplicates its chromosome and divides into two cells.

Generation time (Doubling time)

The time required for a complete fission cycle from parent cell to two daughter cells.

Nitrogen fixation

The calculation of total cells in a population expressed by the formula $N_t = (N_i) 2^n$.

Lag phase

A 'flat' period of growth following inoculation where cells adjustment, enlarge, and synthesize but are not yet multiplying at the maximum rate.

Exponential growth (log) phase

The phase where growth increases geometrically and continues as long as nutrients are adequate and the environment is favorable.

Stationary growth phase

The phase where cell birth and cell death rates are equal, caused by depleted nutrients and waste buildup.

Death phase

The phase where cells begin to die at an exponential rate due to the buildup of wastes; slower than the exponential growth phase.

Viable nonculturable state (VNC)

A dormant state in the death phase where cells remain alive but will not grow on culture medium.

Turbidity

The cloudiness of a nutrient solution that increases as microbes grow, used to analyze population size.

Coulter counter

An electronic device that scans a fluid as it passes through a tiny pipette to count cells.

Flow cytometer

A device that counts cells, measures cell size, and differentiates between live and dead cells.