Ch 4 & 5: Dynamics of Prokaryotic Growth & Laboratory Cultivation and Control (Flashcards)

Key vocabulary terms and concise definitions covering prokaryotic growth, laboratory cultivation, growth curves, environmental/nutritional factors, and control methods (physical and chemical).

Binary fission

Prokaryotic cell division where one cell splits into two; basis of exponential growth.

Exponential growth

Growth pattern where population doubles with each cell division.

Generation time (doubling time)

Time required for a population to double; varies among species.

Nt = N0 × 2^n

Formula for the number of cells after n divisions; Nt is final count, N0 is initial count.

N0

Original number of cells in the population at the start of growth.

Nt

Number of cells in the population after n divisions.

n

Number of cell divisions that have occurred.

Biofilm

Structured community of bacteria attached to surfaces with open channels; resists immune responses and antimicrobials; useful for bioremediation.

Slime layer

A surface-associated coating often part of biofilm architecture.

Planktonic

Free-floating, non-attached bacteria.

Bioremediation

Beneficial use of biofilms to clean up environmental contaminants.

Mixed microbial community

Prokaryotes living together with cooperative and competitive interactions.

Antibiotics (in microbial context)

Toxic substances synthesized by microbes to inhibit competitors.

Pure culture

Population derived from a single cell; all cells genetically identical.

Aseptic technique

Methods to minimize contamination during culturing.

Culture media

Substrates (broth or solid) used to grow bacteria.

Broth

Liquid culture medium.

Agar

Solidifying agent derived from marine algae; melts above 95°C and solidifies around 45°C.

Colony

Visible cluster of cells on solid media originating from a single cell.

Single cell origin

All cells in a colony descend from one progenitor cell.

Streak-plate method

Technique to isolate bacteria by progressively diluting cells on a solid surface.

Stock culture

Culture stored for use as an inoculum in later procedures.

Agar plate

Petri dish containing solid agar as growth medium.

Agar slant

Solid medium in a test tube slanted for long-term storage.

Glycerol stocks

Long-term storage of cultures at −70°C with glycerol as a cryoprotectant.

Lyophilization

Freeze-drying; preserves cultures by removing water under low temperature and pressure.

Growth curve

Five-stage growth pattern in a closed system: lag, log, stationary, death, prolonged decline.

Lag phase

Phase where cell numbers do not increase; cells prepare for growth.

Log phase

Exponential growth phase; primary metabolites produced.

Primary metabolites

Metabolites required for growth produced during log phase.

Secondary metabolites

Metabolites produced in late log phase that aid survival (e.g., antibiotics).

Stationary phase

Growth rate equals death rate; nutrients exhausted.

Death phase

Viable cell numbers decline; death is exponential and slower than growth.

Prolonged decline

Very gradual decline after most cells are dead; may last months or years.

Colony edge

Cells at the periphery of a colony with more oxygen and resources.

Colony center

Highly dense area with less oxygen; greater competition.

Continuous culture

Maintenance of exponential growth by regularly supplying nutrients and removing waste.

Chemostat

Apparatus that achieves continuous culture by constant nutrient input and waste removal.

Psychrophile

Optimal growth at −5°C to 15°C; typically found in cold environments.

Psychrotroph

Optimal growth at 20°C to 30°C; important in food spoilage.

Mesophile

Optimal growth around 25°C to 45°C; common in many environments.

Thermophile

Optimal growth 45°C to 70°C; often in hot environments.

Hyperthermophile

Optimal growth 70°C to 110°C; usually archaea in extreme heat.

Obligate aerobes

Require oxygen for growth and energy production.

Obligate anaerobes

Cannot tolerate oxygen and may be killed by it.

Facultative anaerobes

Grow with or without oxygen; may use fermentation or anaerobic respiration.

Microaerophiles

Require reduced oxygen levels for growth.

Aerotolerant anaerobes

Do not use oxygen but tolerate its presence; fermentative metabolism.

Neutrophiles

Prefer neutral pH (approximately 5–8 in growth range).

Acidophiles

Thrive at acidic pH (below ~5.5).

Alkalophiles

Grow best at alkaline pH (above ~8.5).

Capnophile

Require increased CO2; grown with candle jars or CO2 incubators.

Anaerobe

Organisms that grow without oxygen; some cannot tolerate O2 at all.

Complex media

Media with varied ingredients and no exact chemical formula.

Chemically defined media

Media with precise, pure chemical components and exact concentrations.

Selective media

Inhibit unwanted organisms; allow only desired organisms to grow.

Thayer-Martin agar

Selective for Neisseria gonorrhoeae; contains antibiotics to suppress other bacteria.

MacConkey agar

Selective for Gram-negative bacteria; differentiates lactose fermenters from non-fermenters.

Differential media

Contain substances that cause distinguishable changes in microbes.

Hemolysis

Destruction of red blood cells; alpha, beta, and gamma types observed on blood agar.

Lactose fermentation indicator

pH indicator in differential media (e.g., MacConkey) showing lactose fermentation as color change.

Growth factors

Vitamins, amino acids, and other compounds required by some organisms for growth.

Photoautotroph

Energy from sunlight; carbon from CO2; primary producers.

Chemolithoautotroph

Energy from inorganic chemicals; carbon from CO2; autotrophic bacteria.

Photoheterotroph

Energy from light; carbon from organic compounds.

Chemoorganoheterotroph

Energy from organic compounds; carbon from organic compounds; common in animals.

Plate counts

Viable cell counts on solid media; colonies counted ideally between 30 and 300.

Turbidity

Optical measure of culture density using a spectrophotometer; inversely related to cell concentration.

Autoclave

Sterilization using pressurized steam at 121°C and 15 psi for about 15 minutes; prions require harsher treatment.

Boiling

Kills most microorganisms and viruses but does not destroy endospores.

Pasteurization

Brief heat treatment to reduce pathogens (not sterilization); e.g., 72°C for 15 seconds.

Moist heat

Heat method (steam) used for sterilization or disinfection.

Dry heat

Sterilization method requiring higher temperatures and longer times than moist heat.

Filtration

Physical removal of microbes; membranes trap cells; used for heat-sensitive liquids and air filtration (HEPA).

HEPA

High-efficiency particulate air filter; removes nearly all microbes from air.

Ionizing radiation

Gamma/X-rays that damage DNA; used to sterilize heat-sensitive materials.

Ultraviolet radiation

Non-ionizing radiation that damages DNA; limited penetration; endospores resistant.

High pressure processing

Preserves color and flavor while destroying microbes via extreme pressure (no high heat).

Germicidal chemicals

Chemical agents that kill or inactivate microorganisms by acting on vital cell sites.

FDA

U.S. Food and Drug Administration; regulates antiseptics and related products.

EPA

U.S. Environmental Protection Agency; regulates disinfectants.

Sterilants

Chemicals or processes that destroy all microorganisms, including endospores.

High-level disinfectants

Destroy viruses and vegetative cells; not effective against endospores.

Intermediate-level disinfectants

Kill vegetative cells, fungi, and most viruses; not endospores.

Low-level disinfectants

Remove fungi, vegetative bacteria, and enveloped viruses; not mycobacteria or endospores.

Alcohols

Germicidal chemical class used for disinfection (e.g., ethanol, isopropanol).

Aldehydes

Germicidal chemicals (e.g., formaldehyde) used for sterilization/filtration decontamination.

Nitrates and nitrites

Chemical preservatives in foods; inhibit spore germination and bacterial growth.

Freezing

Low-temperature storage that essentially stops microbial growth; some cells may die.

Desiccation

Drying to reduce water activity; many microbes are inhibited or killed.

Salting

Increasing solute (osmotic) pressure to reduce water availability for microbes.

Endospores

Highly resistant bacterial spores that survive harsh conditions.

Prions

Infamously resistant infectious proteins requiring extreme decontamination.

Nosocomial infections

Hospital-acquired infections; heightened concern for antimicrobial resistance.