Culturing Microorganisms

Culture

Act of growing bacteria or means the microorganisms themselves growing in a nutrient broth or on a solid media

Pure Culture

One species of bacteria

Mixed Culture

Two or more species of bacteria

Inoculate

Add bacteria to a nutrient broth or a solid agar

Liquid Broth

Contains all the essential elements, biochemicals, and minerals bacteria need to grow, appears cloudy or turbid when bacteria is present

Grow Bacteria Quickly

What is liquid broth used for?

Agar

A polysaccharide that is gelatinous at room temperature and obtained from species of red seaweed

Storage or biochemical tests

What are agar slants used for?

Individual colors or antibiotic susceptibility tests

What is agar plates used for?

Colony Forming Unit (CFU)

A colony growing on an agar plate contains thousands of bacteria cells that arose from a single parent cell

Lawn

Too many cells were added to an agar plate and colonies form one continuous film

Aseptic Technique

Used to transfer bacteria from one media type or culture to a new one while avoiding cross contamination

3 way streak Culture

Each sequential streak has less cells or is more dilute, goal is to obtain individual colonies.

First has highest concentration of cells

Last has the least concentration of cells

Pouring Plates

Initial liquid culture is diluted several times through a serial dilution, typically a 1 to 10 dilution is performed. Each dilution will have less cells and will have more colonies to work with

Pure Media

The exact chemical composition is known. All quantities of biochemical or inorganic chemicals are known

Complex Media

Complex materials of biological origin. Exact amounts of biochemicals are usually unknown

Ex. Beef, blood, milk, etc.

Selective Media

Contains specific ingredients that inhibit the grow of some species while promoting the growth of others

Differential Media

This will cause a change the physical appearance certain species of microbes allowing you to distinguish between multiple microbes present. Media itself may also change due to the presence of particular microbes

Anaerobic Media

Slab culture or liquid cultures where the levels of oxygen differ or chambers with the complete absence of oxygen.

Candle jar/Thioglycollate

Transport Media

Used specifically as temporary storage of microbes, transport from point a to b

Refrigeration

Slows down microbial growth and allows from short periods of storage

Deep Freezing

Cultures are stored at temperatures that completely halt growth (-80C)

Lyophilization

Cultures are completely dried out or desiccated

Days to Months

What is the storage time of refrigeration?

Years

What is the storage time of deep freezing?

Decades

What is the storage time of lyophilization

Generation TIme

The time required for a bacterial cell to grow and divide, dependent on physical and chemical conditions.

Binary Fission

Bacterial Cells divide asexually, creating an exact copy of itself

Lag Phase

Characterized by cellular activity but not microbial growth, population size does not increase. Synthesize proteins necessary for growth but need to get used to new environment before they make the decision to grow and devide

Log Phase

Bacteria cells are dividing by cell division and doubling in numbers after each generation time. Metabolic activity is high, plenty of resources and space, low metabolic waste

Stationary Phase

Number of dividing cells equals the number of dying cells. There is no population growth in this phase

Death Phase

Number of dying cells is higher than the number of actively dividing cells, population size decreases. Nutrients are depleted and metabolic wastes become very high