Bacterial Growth and Cultivation

This set of vocabulary flashcards covers key terms and concepts related to bacterial growth principles, cultivation methods, and environmental factors influencing bacterial life, as discussed in the lecture notes.

Binary fission

A form of asexual reproduction in which one cell splits into two, leading to exponential growth.

Generation time

The time it takes for a bacterial population to double in number, which is species-specific.

Exponential growth equation

Nt = N0
× 2n, where Nt is the total number of cells, N0 is the starting number of cells, and n is the number of divisions.

Biofilms

Multicellular associations of bacteria that attach to surfaces and increase their survival.

Planktonic bacteria

Free-floating bacteria that are not attached to a surface.

Polysaccharide slime

A substance produced by bacteria in biofilms that helps other bacteria attach.

Pure culture

A population of cells derived from a single parent cell, making them genetically identical.

Robert Koch

The scientist credited with developing methods for obtaining pure cultures.

Aseptic technique

Procedures used to prevent unwanted microbial contamination.

Broth media

Liquid culture medium used for growing large populations of bacteria.

Solid media (agar)

A culture medium solidified with agar, an extract from marine algae, used to grow bacterial colonies.

Visible colonies

Visible masses on solid media, typically containing about 1 million bacterial cells.

Streak-plate method

The most common laboratory method for isolating individual bacterial colonies by diluting bacteria across a surface.

Closed/batch system

A laboratory growth environment where no new nutrients are added and no waste products are removed.

Growth curve

A graphical representation of the distinct phases of bacterial growth in a closed system.

Lag phase

The initial phase of bacterial growth where cells prepare for division, are metabolically active, but do not yet increase in number.

Log (exponential) phase

The phase of rapid, exponential bacterial doubling.

Primary metabolites

Compounds produced during the log phase that are essential for bacterial growth.

Secondary metabolites

Compounds (like antibiotics) produced in the late log phase, often for survival or competition.

Stationary phase

The phase of bacterial growth where the rate of cell growth equals the rate of cell death, often due to nutrient depletion.

Death phase

The phase where the number of viable bacterial cells declines exponentially.

Prolonged decline phase

A phase following the death phase where most cells die, but the fittest survivors can persist for extended periods.

Continuous culture

A method of culturing bacteria where fresh nutrients are continuously added and waste products are continuously removed.

Chemostat

A device used to maintain bacteria in continuous culture, allowing for ongoing exponential growth.

Psychrophiles

Bacteria that thrive in cold temperatures, typically between -50C and 150C (e.g., Arctic/Antarctic regions).

Psychrotrophs

Bacteria that can grow in cold temperatures, typically between 200C and 300C, often associated with food spoilage.

Mesophiles

Bacteria that grow optimally in moderate temperatures, typically between 250C and 450C, including most human pathogens.

Thermophiles

Bacteria that thrive in hot temperatures, typically between 450C and 700C (e.g., hot springs).

Hyperthermophiles

Archaea that grow in extremely hot environments, typically between 700C and 1100C (e.g., hydrothermal vents).

Obligate aerobes

Bacteria that require oxygen for growth.

Obligate anaerobes

Bacteria that cannot survive in the presence of oxygen.

Facultative anaerobes

Bacteria that prefer oxygen but can grow without it through fermentation.

Microaerophiles

Bacteria that require low concentrations of oxygen for growth; higher levels are toxic.

Aerotolerant anaerobes

Bacteria that do not use oxygen for metabolism but can tolerate its presence.

Neutrophiles

Bacteria that grow optimally at a neutral pH, typically between 5 and 8 (optimum around 7).

Acidophiles

Bacteria that thrive in acidic environments, with an optimum pH below 5.5.

Alkalophiles

Bacteria that thrive in alkaline environments, with an optimum pH above 8.5.

Osmotolerant

Microbes that can tolerate high salt concentrations.

Halophiles

Microbes that require high salt concentrations for growth.

Growth factors

Organic compounds (like vitamins or amino acids) that some bacteria cannot synthesize and must obtain from their environment.

Fastidious bacteria

Bacteria that have complex nutritional requirements, needing many specific growth factors.

Phototrophs

Organisms that use sunlight as their primary energy source.

Chemotrophs

Organisms that obtain energy from chemical compounds.

Autotrophs

Organisms that use carbon dioxide (CO₂) as their main carbon source.

Heterotrophs

Organisms that obtain carbon from organic molecules.

Photoautotrophs

Organisms that use sunlight for energy and CO₂ as their carbon source (e.g., plants).

Chemolithoautotrophs

Organisms that use inorganic chemicals for energy and CO₂ as their carbon source.

Photoheterotrophs

Organisms that use sunlight for energy and organic carbon as their carbon source.

Chemoorganoheterotrophs

Organisms that use organic chemicals for energy and organic carbon as their carbon source (e.g., humans, animals).

Complex media

Culture media with ingredients of variable, not exact, chemical composition (e.g., nutrient broth).

Chemically defined media

Culture media with a precisely known chemical composition, used in research.

Selective media

Culture media designed to allow the growth of certain microbes while inhibiting others.

MacConkey agar

A selective medium that favors the growth of Gram-negative bacteria.

Thayer-Martin agar

A selective medium specifically used for the isolation of Neisseria gonorrhoeae.

Differential media

Culture media that allow for the visualization of differences between types of bacteria, often by changes in color or appearance.

Blood agar

A differential medium used to observe hemolytic reactions (clear zones) caused by bacterial enzymes.

Capnophiles

Bacteria that require elevated levels of carbon dioxide (CO₂) for optimal growth.

Anaerobic cultivation

Methods used to grow anaerobic bacteria by creating an oxygen-free environment (e.g., anaerobic jar, sodium thioglycollate media).

Direct cell counts

Methods used to count the total number of cells, including both live and dead.

Direct microscope count

A direct cell counting method that involves counting cells under a microscope, requiring at least 10 million cells/mL.

Coulter counter

An instrument that counts cells by sensing changes in electrical resistance as they pass through an aperture.

Flow cytometer

An instrument that counts cells by detecting and analyzing light scattered by individual cells as they pass through a laser beam.

Viable cell counts

Methods used to count only the living, reproducing cells in a population.

Plate counts

A viable cell counting method where each colony is assumed to have originated from a single live cell.

Membrane filtration

A viable cell counting method where a liquid sample is filtered, and bacteria on the filter are cultured to form colonies.

Most probable number (MPN)

A statistical method used for estimating the number of viable cells in a liquid sample based on dilutions.

Turbidity

A measure of bacterial biomass by assessing the cloudiness of a liquid culture using a spectrophotometer.

Durham tube

A small inverted tube placed in culture broth to collect gas produced by microbial fermentation.

Luciferase

An enzyme that produces light in the presence of ATP, used to detect microbial presence and metabolic activity.