Experiment 14 | food contamination

What is the right amount of colonies to have in a plate (think tftc tntc)

30-300

What is a limitation of the standard plate count? (think about the medium that is being used)

Only bacteria capable of growing in the culture medium used will form isolated colonies and can be counted

What does selective mean for media? (designed to in_ the gr_)

Selective media are designed to inhibit the growth of certain types of bacteria while allowing others to grow, facilitating the isolation of specific microbial species.

What does differential mean for media?(designed to do what between 2 t_ of bac_)

Differential media are designed to distinguish between different types of bacteria based on their biochemical properties, allowing for the identification and differentiation of species.

What type of media is the EMB agar? And what does it select for (g- or g+)

EMB agar is both selective and differential media used to isolate and differentiate gram-negative bacteria.

How is EMB agar differential as well?(fer_ of la_)

EMB agar is differential because it contains dyes that change color based on the fermentation of lactose by bacteria, allowing for the distinction between lactose fermenters and non-fermenters.Additionally, colonies of lactose fermenters typically appear purple or black, while non-fermenters remain clear or colorless.

On an EMB agar what color will the colonies of bacteria turn to if they ferment lactose

very dark pink/purple

What colors would the non lactose fermenters look like?

clear or colorless

Is Salmonella shigella (ss) agar a selective or differential media?

both.

How is ss agar selective?

inhibits gram +

How is ss agar differential? (same as last think la_)

distinguishes lactose fermenters from non-fermenters by color change.

What color will colonies be that ferment lactose on an ss agar

red