Microbial Growth

This set of flashcards covers essential vocabulary and concepts regarding microbial growth, including definitions of key terms, requirements for bacterial growth, and methods of culturing and preserving bacteria.

Microbial Growth

Refers to the increase in number of organisms, primarily bacteria.

Growth Requirements

The essential conditions and nutrients needed for microbial growth, divided into physical and chemical categories.

Physical Requirements

Factors such as temperature, pH, and osmotic pressure that influence bacterial growth.

Temperature Range

The specific minimum, optimum, and maximum temperatures at which different bacteria can grow.

pH

A measure of acidity or alkalinity of a solution, important for bacterial survival, typically 6.5-7.5 for many bacteria.

Osmotic Pressure

The pressure required to prevent the flow of water across a semipermeable membrane; crucial for bacterial cell integrity.

Chemical Requirements

Essential nutrients like carbon, nitrogen, sulfur, phosphorous, trace elements, and organic growth factors needed for microbial growth.

Autotrophs

Organisms that obtain carbon from fixing atmospheric carbon dioxide.

Heterotrophs

Organisms that obtain carbon from the breakdown of organic compounds.

Deep Freezing

A method used to preserve bacterial cultures by rapid freezing with a cryoprotectant.

Biofilms

Complex microbial communities that form through the aggregation of bacteria in a protective layer of extracellular polymeric substance.

Quorum Sensing

The process by which bacteria communicate and coordinate behavior through chemical signaling.

Selective Media

Culture media designed to encourage the growth of a specific organism while inhibiting others.

Psychrotrophs

organisms that grow at low temperatures, typically at or below 20°C, often causing food spoilage.

Obligate halophiles

organisms that require high salt concentrations for growth, commonly found in salt lakes and salt mines.

Catalase

an enzyme that breaks down hydrogen peroxide into water and oxygen, protecting cells from oxidative damage.

Inoculum

the introduction of microbes into a culture medium to initiate growth.

Chemically defined media

culture media with known chemical composition, allowing precise control of nutrients provided to microbes.

Incubator

a device used to maintain optimal temperature and conditions for microbial growth in laboratory settings.

Stationary Phase

The phase of microbial growth where the rate of cell division equals the rate of cell death, leading to a constant population size.

Spread plating

A microbiological technique used to isolate and quantify microorganisms by spreading a diluted sample evenly on the surface of an agar plate.

Extracellular polymeric substance

A complex mixture of polysaccharides, proteins, and nucleic acids produced by microbial cells that helps in forming biofilms and provides structural stability.

Facultative halophiles

Microorganisms that can tolerate and thrive in high salt concentrations, but do not require them for growth.

Psychrophiles

Microorganisms that thrive in cold temperatures, typically between -20°C and 10°C. They are commonly found in polar regions and deep sea environments.

Culture media 

Substances used to support the growth of microorganisms in laboratory settings, providing essential nutrients and conditions for various types of microbes.

Culture

A method of growing microorganisms in controlled conditions to study their behaviors and characteristics.

Agar

A gelatinous substance derived from algae, commonly used as a solidifying agent in culture media to grow bacteria and other microorganisms.

Anaerobic jar

A specialized container used to cultivate anaerobic bacteria by creating an oxygen-free environment.

Differential media

A type of culture medium that distinguishes between different microorganisms based on their biochemical characteristics, allowing for easy identification.

Log phase

Also known as the exponential phase, is the period of microbial growth where cells divide at a constant and rapid rate, leading to a significant increase in population size.

Death phase

The stage in microbial growth where the number of viable cells decreases significantly due to nutrient depletion and toxic accumulation.

Snap freezing

A method of rapidly freezing biological samples to preserve cellular structures and function, often used in microbial culture preservation.

Mesophiles

Microorganisms that thrive in moderate temperature ranges, typically between 20°C and 45°C, and are often responsible for human infections.

Acidophiles

Microorganisms that thrive in acidic environments, typically with a pH of 3 or lower, and can be found in locations like acid mine drainage.

Superoxide dismutase

An enzyme that catalyzes the conversion of superoxide radicals into oxygen and hydrogen peroxide, playing a crucial role in protecting cells from oxidative damage.

Inoculation

The introduction of microorganisms into a culture medium to initiate growth, often used in laboratory settings for testing and propagation.

Complex media

Nutrient-rich formulations that support growth of a wide variety of microorganisms, containing various organic and inorganic compounds.

Reduced media

Media that contains agents to reduce oxygen levels, promoting the growth of anaerobic organisms.

Pure culture

A laboratory culture containing a single type of microorganism, free from contamination by other species, essential for studying specific growth characteristics.

Enrichment media

Specialized media that enhances the growth of specific microorganisms while inhibiting others. Used to isolate particular types of bacteria from mixtures.

Lag phase 

The initial phase of microbial growth where bacteria adapt to their new environment, with little to no cell division occurring.

Pour plating

A microbiological technique where a diluted microbial sample is mixed with melted agar and poured into a plate, allowing colonies to grow throughout the medium.

Lyphilization

A method of preserving microorganisms by freezing them and then removing water through sublimation, leading to a dry state that can be rehydrated later.

Carbon

constitutes 50% of the dry weight; obtained from CO2 (autotrophs) or organic compounds (heterotrophs) 

Hydrogen

critical for energy generation; typically supplied by water

Nitrogen

accounts for about 14% of dry mass; used in amino acids and nucleic acids

Sulfur

used for amino acids and vitamins; usually derived from hydrogen sulfide or organic breakdown 

Phosphorus

integral for DNA, RNA , and ATP structure; typically required in phosphate form

Trace Elements

potassium, magnesium, calcium; used in small amounts as enzyme cofactors

Organic growth factors

Essential organic compounds required for growth, such as amino acids, vitamins, and purines.

Oxygen

essential for aerobic life but toxic to cells in certain forms

The increase in number of organisms, primarily bacteria, is referred to as __.

Microbial Growth

The essential conditions and nutrients needed for microbial growth are categorized as __.

Growth Requirements

Organisms that obtain carbon from fixing atmospheric carbon dioxide are known as __.

Autotrophs

__ are organisms that obtain carbon from the breakdown of organic compounds.

Heterotrophs

Complex microbial communities formed by the aggregation of bacteria within a protective extracellular polymeric substance are called __.

Biofilms

Bacteria communicate and coordinate behavior through chemical signaling, a process known as __.

Quorum Sensing

__ is a type of culture media designed to encourage the growth of a specific organism while inhibiting others.

Selective Media

Microorganisms that thrive in cold temperatures, typically between -20°C and 10°C, are known as __.

Psychrophiles

During the __ of microbial growth, the rate of cell division equals the rate of cell death.

Stationary Phase

A laboratory culture containing a single type of microorganism, free from contamination, is called a __.

Pure culture

The enzyme __ breaks down hydrogen peroxide into water and oxygen, protecting cells from oxidative damage.

Catalase

The initial phase of microbial growth, where bacteria adapt to their new environment with little to no cell division, is called the __.

Lag phase