Topic 2 - Nutrition and growth - micro unit 2.1

Vocabulary flashcards covering key terms related to bacterial nutrition, growth requirements, stress responses, environmental adaptations, and laboratory measurement techniques.

Autotroph

Organism that uses carbon dioxide as its sole carbon source.

Heterotroph

Organism that requires pre-formed organic compounds for carbon; also called organotroph.

Chemoorganotroph

Heterotroph that obtains energy from oxidation of organic molecules; includes most medically important bacteria.

CHONPS

Acronym for the six major elements needed in large amounts: carbon, hydrogen, oxygen, nitrogen, phosphorus, sulfur.

Macronutrient (minerals)

Element such as Ca²⁺, Fe³⁺, Mg²⁺, or K⁺ required in moderate quantities.

Micronutrient (trace element)

Metal ion such as Zn²⁺, Mo²⁺, or Mn²⁺ needed only in very small amounts.

Growth factor

Organic compound (vitamin, amino acid, blood component, etc.) that some bacteria must obtain from their environment.

Siderophore

Bacterial molecule that scavenges and transports iron across membranes.

Hemolysin

Bacterial toxin that lyses red blood cells to release iron and other nutrients.

Fastidious organism

Bacterium that requires numerous growth factors or special media to grow.

Oligotroph

Microbe adapted to environments with very low nutrient concentrations.

Copiotroph

Microbe that thrives in nutrient-rich environments; grows rapidly in the lab.

Semi-starvation state

Reduced metabolic activity and smaller cell size in response to nutrient limitation.

Sporulation

Process by which some bacteria form highly resistant endospores under stress.

Endospore

Dormant, thick-walled structure formed inside certain bacteria for survival, not reproduction.

Compatible solute

Small neutral molecule accumulated inside cells to counteract external hypertonic conditions.

Heat-shock protein

Stress protein expressed by bacteria to protect cellular components from high-temperature damage.

Defined medium

Culture medium containing known amounts of pure chemicals.

Complex medium

Culture medium containing extracts or hydrolysates with unknown exact composition.

Selective medium

Culture medium that inhibits unwanted microbes while permitting growth of desired ones.

Differential medium

Culture medium that allows visual distinction between different microbial types.

Suffix “-phile”

Indicates an organism that prefers or requires a particular condition (e.g., thermophile).

Suffix “-tolerant”

Indicates an organism that can withstand but does not prefer an extreme condition (e.g., halotolerant).

Catalase

Enzyme that converts hydrogen peroxide into water and oxygen, protecting cells from oxidative damage.

Superoxide dismutase

Enzyme that converts superoxide radicals to peroxide and oxygen, enabling aerobic life.

Obligate aerobe

Organism that requires oxygen for metabolism and growth.

Microaerophile

Obligate aerobe that grows only at low oxygen concentrations.

Facultative anaerobe

Organism that can grow with or without oxygen, using aerobic respiration when O₂ is present.

Aerotolerant anaerobe

Anaerobe that does not use oxygen but is not harmed by its presence.

Obligate (strict) anaerobe

Organism inhibited or killed by oxygen due to lack of protective enzymes.

Psychrotroph

Bacterium that grows at room temperature but can also proliferate in a refrigerator; causes food spoilage.

Thermoduric

Bacterium able to survive brief exposures to high temperatures.

Acidophile

Organism that grows optimally at low pH values.

Alkalophile

Organism that grows optimally at high pH values.

Halophile

Organism that requires or tolerates high salt concentrations for growth.

Osmophile

Microbe that thrives in environments with high solute (sugar, salt) concentrations.

Xerotolerant

Organism capable of surviving very dry conditions.

Deinococcus radiodurans

Extremely radiation-resistant bacterium with highly efficient DNA repair systems.

Barophile

Microbe that requires high hydrostatic pressure, such as that in deep-sea environments.

Generation time

Time required for a bacterial population to double in number.

Lag phase

Initial period of a growth curve when cells adapt to medium and prepare for division.

Log (exponential) phase

Growth phase in which bacterial cells double at regular intervals.

Stationary phase

Growth phase where cell division rate equals death rate; total population stabilizes.

Decline (death) phase

Final growth phase characterized by net loss of viable cells.

N = N₀ × 2ⁿ

Formula describing exponential bacterial growth, where n equals the number of doublings.

Petroff-Hausser counting chamber

Microscope slide with etched grid used for direct counting of cells in a known volume.

Coulter counter

Automated instrument that counts cells by detecting electrical resistance changes as cells pass through an aperture.

Viable plate count

Method that estimates bacterial numbers by counting colonies formed on agar plates from diluted samples.

Optical density (OD)

Measure of culture turbidity used to estimate cell concentration; does not distinguish live from dead cells.