Chapter 9: Introduction to Microbial Nutrition, Transport, Growth, and Ecological Interactions

Vocabulary flashcards covering key terms and concepts from microbial nutrition, transport, growth, and ecological interactions discussed in the lecture notes.

CHONPS

The six essential elements for life: Carbon, Hydrogen, Oxygen, Nitrogen, Phosphorus, and Sulfur (often grouped as CHONPS); required by microbes for growth.

Macronutrients

Nutrients required in large amounts for growth (examples include CHON elements and other inorganic ions for structural and metabolic purposes).

Micronutrients (trace elements)

Nutrients required in small amounts that often serve as cofactors in enzymatic reactions.

Cofactor

Nonprotein chemical compounds or metal ions that assist enzymes in catalysis.

Heterotroph

An organism that obtains carbon from organic compounds (uses organic nutrients for growth).

Phototroph

An organism that uses light as an energy source to drive metabolism.

Photoautotroph

A phototroph that uses light energy to fix CO2 into organic matter (produces organic compounds from CO2).

Chemotroph

An organism that derives energy from chemical reactions rather than light.

Chemoautotroph

An organism that obtains energy from inorganic chemical reactions and fixes CO2 (carbon source from CO2).

Chemoorganoheterotroph

An organism that uses organic compounds for both energy and carbon (a subset of chemotrophs).

Methanogen / Methanogenesis

Microbes in anaerobic environments that produce methane (CH4) as a metabolic byproduct.

Saprobe / Saprotroph

An organism that feeds on dead or decaying organic matter (decomposer).

Parasite

An organism that lives on or in a host and harms the host, benefiting the parasite rather than the host.

Symbiosis

A close, long-term interaction between two or more different organisms.

Mutualism

A type of symbiosis where both organisms benefit from the relationship.

Commensalism

A type of symbiosis where one partner benefits and the other is neither helped nor harmed.

Parasitism

A relationship where one organism benefits at the expense of the other host.

Biofilm

A structured, surface-attached microbial community encased in a self-produced matrix.

Quorum sensing

Cell-to-cell communication in microbial populations that coordinates gene expression based on population density.

Diffusion

Movement of solutes from a region of high concentration to low concentration without energy input.

Osmosis

Diffusion of water across a selectively permeable membrane from low solute concentration to high solute concentration.

Isotonic

A solution with the same solute concentration as the cell interior, resulting in no net water movement.

Hypotonic

A solution with lower solute concentration than the cell interior; water tends to move into the cell.

Hypertonic

A solution with higher solute concentration than the cell interior; water tends to move out of the cell.

Simple diffusion

Diffusion across a membrane without the aid of transport proteins.

Facilitated diffusion

Diffusion that requires specific membrane transport proteins; saturable and does not use energy.

Saturation (transport)

When transport proteins’ binding sites are fully occupied, limiting the rate of transport.

Active transport

Energy-dependent transport that moves substances against their gradient via pumps (e.g., Na+/K+ pump, proton pumps).

Sodium-Potassium Pump (Na+/K+ pump

A membrane pump that maintains electrochemical gradients by pumping Na+ out and K+ in; essential for osmotic balance.

Proton pump

A membrane transporter that moves protons to generate a proton motive force used for ATP synthesis.

Aerobe

An organism that requires oxygen for metabolism.

Obligate aerobe

An organism that absolutely requires oxygen and cannot grow without it.

Obligate anaerobe

An organism that cannot tolerate oxygen and lacks the enzymes to detoxify reactive oxygen species.

Facultative anaerobe

An organism that can grow with or without oxygen; prefers oxygen but can ferment or respire anaerobically when oxygen is absent.

Aerotolerant anaerobe

An organism that does not use oxygen but can survive in its presence.

Psychrophile (cyclophile)

An organism with an optimum growth temperature below 15°C; can grow at 0°C but not above ~20°C.

Mesophile

An organism with an optimum growth temperature around human body temperature (roughly 20–40°C).

Thermophile

An organism with an optimum growth temperature above 45°C; extreme thermophiles can tolerate 80–121°C.

Barophile

An organism that thrives under high hydrostatic pressure, such as deep-sea environments.

Halophile

An organism that requires or tolerates high salt concentrations for growth.

Acidophile

An organism that grows best in acidic environments (low pH).

Alkalinophile (alkalinophile)

An organism that grows best in alkaline environments (high pH).

Reactive oxygen species (ROS)

Damaging byproducts of oxygen, such as superoxide and hydrogen peroxide, that organisms must manage.

Superoxide dismutase (SOD)

An enzyme that dismutates superoxide radicals into oxygen and hydrogen peroxide, reducing oxidative damage.

Catalase

An enzyme that decomposes hydrogen peroxide into water and oxygen.

Hydrogen peroxide (H2O2)

A reactive oxygen species produced by immune responses and metabolism; decomposed by catalase and other enzymes.

Lag phase

Initial growth phase where cells adapt; little to no cell division occurs.

Log (exponential) phase

Phase of rapid, exponential growth where cells divide at a constant rate.

Stationary phase

Phase where growth rate slows and equals the death rate due to limited nutrients and space.

Death phase

Phase where cells die at an accelerated rate due to severe resource depletion and waste accumulation.

Generation time / Doubling time

The time required for a microbial population to double in number; often used in growth calculations.

Two to the power n (2^n)

Mathematical expression for exponential growth where n is the number of generations.

Growth curve

A plot of population size versus time showing lag, exponential, stationary, and death phases.