Investigating Antibiotics And Antiseptics Flashcards
what is grown and cultured in growth mediums
bacteria and some other microorganisms
what does a growth medium contain
- carbohydrates
- minerals
- proteins
- and vitamins they need to grow
what are the two things the growth medium could be
- a nutrient broth solution
- or solid agar jelly
what do bacteria grown on agar plates form
- visible colonies on the surface of the jelly
- which could spread out to give an even covering
how do you make an agar plate
- hot agar jelly is poured into petri dishes
- when jelly cools and sets, incoulating loops are used to transfer microorganisms to the agar jelly
- the microorganisms then multiply
what is a petri dish
a shallow round plastic dish
how could you alternatively place the microorganisms on the agar jelly
- use a sterile dropping pipette to drop the microorganisms on to the jelly
- and use a spreader to get an even covering of bacteria
why are cultures of microorganisms kept at 25C in school
harmful pathogens are less likely to grow at this temperature
how is temperature managed when growing bacteria outside of school
- you may culture microorganisms at a higher temperature
- to provide the optimum conditions for growth
what do antibiotics simply do
they kill bacteria inside the body
what do antiseptics simply do
they kill bacteria outside the body
what can you use to investigate the effect of antiseptics and antibiotics
cultures of bacteria
what is the process of investigating the effects of antibiotics (and antiseptics alike)
- soak paper disks soaked in different types of antibiotics on an agar plate with an even covering of bacteria
- leave some space between the discs
- the antibiotic should diffuse into the agar jelly
- leave the plate for 48 hours at 25C
what will antibiotic resistant bacteria do on the agar jelly compared to non-resistant bacteria
- the resistant bacteria will continue to grow on the agar around the paper discs
- while the non-resistant bacteria will die
what is the inhibition zone
the clear area that is left where the bacteria have died
what is the control in this experiment and why should you use it
- a paper disc that has not been soaked in an antibiotic
- you should use it because you can be sure that any difference between the growth of the bacteria around the control disc and the antibiotic disc is due to the effect of the antibiotic alone
how will a more effective antibiotic against the bacteria be shown after the time is up
the antibiotic will have a larger zone of inhibition
how do you avoid contamination by unwanted microorganisms which can affect your results
by using aseptic conditons
what are the five things you can do to make sure the bacteria is in aseptic conditons
- sterilise petri dishes and growth medium
- sterilise the incoulating loop
- keep liquid cultures in a culture vial with a lid
- cover the petri dish with a lid
- store the petri dish upside down
how do you sterilise the petri dishes and growth medium
- by placing them in a machine called an autoclave
- which uses steam at a high pressure and temperature to kill any microorganisms present
how should the incoulating loop be sterilised
- by passing it through a flame
- so that any unwanted microorganisms are killed
why should you keep liquid bacteria cultures in a cultural vial with a lid
- to prevent other microbes from getting in
- you should only be briefly removing the lid when transferring the bacteria
why should the petri dish be stores upside down
to stop drops of condensation falling onto the agar jelly
