btls making media + testing plants

also lorenzo

what types of media will e coli bacteria grow in?

nutrient, blood, potato, dextrose, LB agar

what does the LB in LB agar stand for?

luria bertani

what is a media base?

a dry mixture of media components

media prep equation

mass/volume = mass/volume

how many days in advance should a broth culture be started

1-2 days

when is innoculating loop flame sterilized?

before starting, in between each streak, at the end

plates are labelled on the

bottom

when pouring, you should flame sterilize

the top of the bottle 3 times

how much should you fill the plate with agar?

to about ½ the height of the petri dish

how long does it take for the agar in plates to solidify after pouring?

15 minutes

proper disposal of agar?

thrown in trash, NOT in the sink

what is the goal of streaking bacteria?

to separate isolated colonies on the surface of a plate.

how should the inoculating loop be held when streaking plates?

parallel

what are the 3 goals/things to remember about streaking plates?

1. to have fewer bacterial colonies in each successive streak

2. to only go through the previous streak one time

3. flame sterilize between streaks

when streaking plates, what is the formation that should be used?

z technique

how do you cool the inoculating loop after flame sterilizing?

lightly put tip of inoculating loop to the agar at the edge of the plate and let rest for a few seconds

what is the purpose of the testing plants lab?

to ascertain what locally found plant materials contain active ingredients that will inhibit the growth of bacteria

what was the negative control in this lab?

the disk soaked in deionized h2o

what was the positive control in this lab?

the ampicillin soaked disk

what are 3 potential sources of error in the experiment’s design that could give false data?

1. incorrectly making the agar or broth

2. outside contamination

3. too much time in the incubator

what could be the benefit of using methanol as an extraction solution instead of deionized water?

methanol separates polar molecules. however it kills bacteria, making it not applicable for this lab

where is the bleach bin located?

in the back of the room

when is the bleach bin used?

when anything comes into contact with bacteria, it must go to the bleach bin to be properly sterilized.

why do we parafilm our plates?

it prevents moisture and volume loss and prevents contamination.

why must a plate culture be grown upside down?

because if grown right side up the condensation on the lid of the plate will drip down onto the sample, causing contamination

after streaking a plate with a colony of e. coli cells and incubating it overnight at 37 degrees C, a technician returns to find no colonies on the plate. list 3 viable reasons why this could happen.

1. there could have contamination in the plate

2. he could have made his agar incorrectly, resulting in no growth

3. he could have taken too little of a bacteria sample that he put on the petri dish

you make 1 L of LB agar and pour it into 5 media bottles for sterilization. adter autoclaving and cooling them, you notice some of the bottles have agar that is not completely solid, while other bottles do have solidified agar as expected. what should you do? are any of them useable? if so, which owns?

neither of them are useable, because the ratio distribution of the LB agar is very uneven, so even though the other bottle appears useable, it could very possibly be defective and should not be used