Microbial Requirements Part 2: Nutrient Transport and Temperature Adaptations

Comprehensive vocabulary flashcards covering microbial nutrient absorption, membrane transport mechanisms, osmotic conditions, and temperature adaptations from Dr. Katrina D. Keith's lecture.

Cell Membrane

A semi-permeable structure specialized for transport across which necessary nutrients are taken into the cell and waste materials are exported, unlike the cell wall which is too nonselective.

Diffusion

The movement of molecules in a gradient from an area of higher density or concentration to an area of lower density or concentration, governed by the concentration gradient and membrane permeability.

Osmosis

A specific type of diffusion defined as the movement of water across a selectively permeable membrane toward the side with higher solute concentration until equilibrium is reached.

Selective Membrane

A membrane whose transport is based on specific molecular traits and actively regulated by the cell using active transport, protein channels, gates, and often $ATP$ to pump molecules against a gradient.

Differential Membrane

A purely passive membrane that separates substances based strictly on physical properties like size or charge acting like a sieve, requiring no energy and relying on pore size and simple diffusion.

Isotonic Conditions

An environment where the solute concentration outside the cell equals that inside the cell, resulting in water diffusing at the same rate in both directions and providing the most stable state for cells.

Hypotonic Conditions

An environment where the solute concentration outside the cell is lower than inside, driving the net diffusion of water into the cell and causing cells lacking walls to swell and burst.

Hypertonic Conditions

An environment where the solute concentration outside the cell is higher than inside, exerting high osmotic pressure that draws water out of the cell and inhibits microbial growth.

Plasmolysis

The process occurring in walled cells exposed to a hypertonic solution where water diffuses out, causing the cytoplasmic membrane to shrink away from the rigid cell wall.

Contractile Vacuole

An energy-requiring adaptation in freshwater amoebas that continuously pumps excess water out of the cell to prevent bursting in hypotonic pond environments.

Haloarchaea

Microorganisms that survive hypertonic environments by taking in salt to make their internal environment isotonic with their surroundings, possessing a physiological requirement for high salinity.

Active Transport

The nutrient transport process moving molecules against a concentration gradient (or with it at an accelerated rate) using specific membrane permeases and pumps, requiring cellular energy to transport substances including $K^+$, $Na^+$, and $H^+$.

Carrier-Mediated Active Transport

A transport mechanism in which atoms or molecules are pumped across the cell membrane by specialized receptor proteins driven by $ATP$ or the proton-motive force.

Group Translocation

A form of active transport driven by $ATP$ where a molecule is moved across the membrane and simultaneously converted into a metabolically useful substance.

Endocytosis

A bulk transport process driven by $ATP$ in which a eukaryotic cell encloses large particles, cells, or liquids in segments of its membrane to form vacuoles or vesicles.

Phagocytosis

A type of endocytosis utilized by amoebas and certain white blood cells that involves extending pseudopods to engulf whole cells or large solid particles into vacuoles.

Pinocytosis

A type of endocytosis where oils or liquids containing dissolved molecules enter the cell via enclosed vesicles formed by membrane folds or microvilli.

Cardinal Temperatures

The species-specific range of temperatures (comprising the minimum, maximum, and optimum temperatures) that permits continued growth and metabolism of a microorganism.

Minimum Temperature

The lowest temperature that permits a microbe's continued growth and metabolism, below which physiological activities are severely limited.

Maximum Temperature

The highest temperature at which microbial growth and metabolism can proceed; exceeding this threshold denatures enzymes and nucleic acids, leading to cell death.

Optimum Temperature

The intermediate temperature range between the minimum and maximum temperatures that promotes the fastest rate of growth and metabolism in a given microbial species.

Psychrophile

An obligate cold-loving microbe with an optimum growth temperature below $15^\circ\text{C}$, capable of growth at $0^\circ\text{C}$, and strictly unable to grow above $20^\circ\text{C}$.

Psychrotolerant

Microbes that are capable of growing slowly in cold environments but have an optimum growth temperature between $15^\circ\text{C}$ and $30^\circ\text{C}$.

Mesophile

Organisms that grow in an intermediate temperature range of $10^\circ\text{C}$ to $50^\circ\text{C}$ with an optimum between $20^\circ\text{C}$ and $40^\circ\text{C}$, comprising the majority of medically significant microbes and human pathogens.

Thermoduric

Microbes that normally grow as mesophiles but can survive short-term exposures to high temperatures, commonly acting as contaminants in pasteurized or heated food products.

Thermophile

Microorganisms that grow optimally at temperatures above $45^\circ\text{C}$ with a general range of $45^\circ\text{C}$ to $80^\circ\text{C}$, inhabiting volcanic soils, water, compost piles, and sun-exposed habitats.

Extreme Thermophile

Hyperthermophilic organisms that thrive at extreme temperatures between $80^\circ\text{C}$ and $121^\circ\text{C}$.

Thermus aquaticus

A thermophilic bacterium isolated from hot springs in Yellowstone National Park that grows at a minimum of $50^\circ\text{C}$, optimal $65\text{--}70^\circ\text{C}$, and maximum $80^\circ\text{C}$, providing the heat-stable Taq polymerase used in PCR.

Chemoorganic Autotroph

An autotrophic organism that uses $CO_2$ as its carbon source and derives its metabolic energy from organic compounds, exemplified by methanotrophs.

Chemolithoautotroph

An autotrophic organism that uses $CO_2$ as its carbon source and obtains energy from inorganic compounds or minerals, exemplified by Thiobacillus ('rock-eating' bacteria).

Saprobe

A chemoheterotrophic decomposer, such as certain fungi and bacteria, that satisfies its carbon and energy requirements by metabolizing the organic matter of dead organisms.