Triple - Bacteria
Bacteria Growth and Antispetics or Antibiotics
Bacteria Growth and Antispetics or Antibiotics
Bacteria
Investigating the growth of bacteria in the presence of antiseptic or antibiotics
Check your understanding with these quick common questions. Use the drop down boxes to see the correct answers.
Independent variable (IV): Antimicrobial type or concentration.
Dependent variable (DV): Size of clear zone (diameter/area) around each disc (inhibition zone).
Control variables: Bacterial species/strain, agar type/depth, incubation temperature & time, inoculum volume and spreading method, disc size & soak time, volume of antimicrobial per disc.
Nutrient agar plates,
bacterial culture (e.g. E. coli),
Inoculating/spreader (glass spreader),
Bunsen burner/bench disinfectant for asepsis,
sterile filter paper discs
clear tape (to secure lids), marker.
Improve accuracy with using photographs and image analysis to measure exact coverage size
Improve validity by ensuring plates are all stored at the same temperature. The bacterial solution is equally spread out.
Antibiotics/Antiseptics diffuse away from the discs. The further they diffuse, the lower the concentration becomes.
The larger the clear zone
The more bacteria have been killed
Because the antibiotics are effective at a lower concentration.
Aseptic set-up; pour/obtain set nutrient agar plates; label.
Spread a standard volume of bacterial suspension to make a uniform lawn.
Using sterile forceps, place soaked discs (different antiseptics/antibiotics or concentrations) evenly spaced.
Tape the lid (not all the way round), invert, and incubate for a set time/temperature.
Measure diameter of zones of inhibition / clear zones with a ruler.
Calculate each zone's area using PiR2