4.3

Pure culture

A population that descends from a single species. Makes it easy to observe species. Everything must be sterile for growth.

Aseptic technique

A set of procedures that minimize the chances that other organisms will be introduced.

Culture medium

Solid gel or liquid broth thats used to help grow microorganisms in the lab by providing nutrients and regulating conditions

How to get pure culture

1) Solid culture medium 2) Container to keep the medium sterile 3) method to separate cells

Colony

A single microbial cell will multiply to form a colony which is a mass of cells. Need one million to see w eyes.

Agar

A polysaccharide extracted from seaweed used to solidify culture media. Microbes cannot degrade it. Melted agar will only harden at 45°C. Melts above 95°C

Streak plate method

A sterile loop is dipped into microbe sample and drawn across 1/3 surface of agar plate. Sterilize and draw more on new portion of plate. Sterilize and draw on third portion. Can store in fridge as agar slant or freezed at -70°C in glycerol containing solution that prevents ice crystals that damage cells

Closed system

System like tubes, flask or agar plate where nutrients aren’t added and waste is not removed

Grow curve

Growth pattern observed when cells are grown in closed system

Lag phase

When microo. are just transferred and they are synthesizing enzymes required for growth

Exponential phase

Cells divide at constant rate. Generations time is measured at this phase. Medically significant. Eventually waste products accumulate. Endospores start sporulation. Other cells prepare for starving

Secondary metabolites

Metabolic products synthesize during late log and stationary phases like antibiotics.

Primary metabolites

Small valuable molecules made during exponential period.

Stationary phase

When nutrients are too low for cells to grow. Viable cells stay constant. Living cells are taking nutrients of the ones that are dying. Cells still make secondary metabolites.

Death phase

Viable cells start dying at a constant rate.

Phase of prolonged decline.

Some cells survive the death phase and adapted to the bad conditions, can still multiple for a little while using the nutrients of dead cells. Eventually they die but some still survive and generate more cells that are more fit for survival than the last one.

Cell location in colony

Broth: All nutrients is mixed together so no need to compete

Colony: After phase, cell multiply and compete w eachother for nutrients. Different cells be be of different stages. Cells at the edge have more nutrients compared to the ones in the middle.

Chemostat

Device used to grow bacteria in lab what allows you to add nutrients and remove waste. Makes is possible to study how populations respond to different nutrient concentrations.