The45Girl
Title: An experimental study on the effectiveness of antibiotics on different bacteria, as
determined by the zone of inhibition
Name: The45Girl
Colleagues: [deleted]
Research question: What is the effect of varying the type of bacteria on which the
antibiotic is applied on the diameter of the zone of inhibition?
Background Theory:
Bacterial infections can be treated with antibiotics, which are compounds that kill or inhibit the
growth of microbes, especially, bacteria, by targeting prokaryotic metabolic features such as
enzymes, 70S ribosomes and formation of the cell-wall. Bactericidal antibiotics kill the bacteria while
bacteriostatic antibiotics only inhibit the ability of the bacteria to reproduce. Antibiotics do not harm
eukaryotes, such as humans, as eukaryotes do not possess prokaryotic metabolic features. (BioNinja,
2017).
Antibiotics were discovered by Alexander Fleming in 1928. His discovery of pencilin paved the way
for many more antibiotics to be developed to treat various infections, whether they were narrow-
spectrum (effective against specific bacteria) or broad-spectrum (effective against many bacteria).
Unfortunately, the widespread use of antibiotics has led to bacteria developing resistance to them.
(BioNinja, 2017).
Humans are increasingly becoming infected by bacteria which are resistant to antibiotics for many
reasons. First, antibiotics are over-prescribed or misused to treat viral infections. Furthermore, many
antibiotics are available without a prescription and livestock feed tends to include antibiotics. Finally,
hospitals are often centres of multi-drug-resistant bacteria, such as those which cause nosocomial
infections, because antibiotics are used regularly there. (BioNinja, 2017).
Antibiotic resistance is the ability of bacteria to resist the lethal effects of antibiotics. When
antibiotics were first used, they were very effective and almost all the bacteria being targeted were
killed. However, some bacteria with genes that provide resistance by degrading the antibiotic,
blocking its entry, increasing its removal or altering the target survived and passed on their genes to
offspring. As bacteria reproduces very quickly, the proportion of bacteria that were resistant to
antibiotics rapidly increased. To worsen matters, resistant strains of bacteria can pass on this
resistance to other strains through bacterial conjugation and some strains are resistance to many
types of antibiotics. (BioNinja, 2017).
There is a possibility that different strains of bacteria have different degrees of resistance to
antibiotics.
References
BioNinja. (2017). Antibiotic Resistance. [online] Available at: http://ib.bioninja.com.au/standard-
level/topic-5-evolution-and-biodi/52-natural-selection/antibiotic-resistance.html [Accessed 23 Nov.
2017].
, The45Girl
BioNinja. (2017). Antibiotics. [online] Available at: http://ib.bioninja.com.au/standard-level/topic-6-
human-physiology/63-defence-against-infectio/antibiotics.html [Accessed 23 Nov. 2017].
Hypothesis
If the antibiotics are applied on different strains of bacteria, then their effectiveness will be altered
because different bacteria have different degrees of resistance to different antibiotics.
Variables
Independent variable:
The type of antibiotic.
The antibiotics used are:
A.P. or Ampicilin (represented by the colour grey on the multidisc).
C. or Chloramphenicol (represented by the colour green on the multidisc).
P.G. or Penicilin G. (represented by the colour pink on the multidisc).
S. or Streptomycin (represented by the colour white on the multidisc).
S.T. or Sulphatriad (represented by the colour mauve on the multidisc).
T. or Tetracycline (represented by the colour brown on the multidisc).
Dependent variable:
The effectiveness of the antibiotics.
This will be determined by the diameter of the zone of inhibition (mm). This will be measured
with a 30 cm ruler with an uncertainty of ±1 mm.
Title: An experimental study on the effectiveness of antibiotics on different bacteria, as
determined by the zone of inhibition
Name: The45Girl
Colleagues: [deleted]
Research question: What is the effect of varying the type of bacteria on which the
antibiotic is applied on the diameter of the zone of inhibition?
Background Theory:
Bacterial infections can be treated with antibiotics, which are compounds that kill or inhibit the
growth of microbes, especially, bacteria, by targeting prokaryotic metabolic features such as
enzymes, 70S ribosomes and formation of the cell-wall. Bactericidal antibiotics kill the bacteria while
bacteriostatic antibiotics only inhibit the ability of the bacteria to reproduce. Antibiotics do not harm
eukaryotes, such as humans, as eukaryotes do not possess prokaryotic metabolic features. (BioNinja,
2017).
Antibiotics were discovered by Alexander Fleming in 1928. His discovery of pencilin paved the way
for many more antibiotics to be developed to treat various infections, whether they were narrow-
spectrum (effective against specific bacteria) or broad-spectrum (effective against many bacteria).
Unfortunately, the widespread use of antibiotics has led to bacteria developing resistance to them.
(BioNinja, 2017).
Humans are increasingly becoming infected by bacteria which are resistant to antibiotics for many
reasons. First, antibiotics are over-prescribed or misused to treat viral infections. Furthermore, many
antibiotics are available without a prescription and livestock feed tends to include antibiotics. Finally,
hospitals are often centres of multi-drug-resistant bacteria, such as those which cause nosocomial
infections, because antibiotics are used regularly there. (BioNinja, 2017).
Antibiotic resistance is the ability of bacteria to resist the lethal effects of antibiotics. When
antibiotics were first used, they were very effective and almost all the bacteria being targeted were
killed. However, some bacteria with genes that provide resistance by degrading the antibiotic,
blocking its entry, increasing its removal or altering the target survived and passed on their genes to
offspring. As bacteria reproduces very quickly, the proportion of bacteria that were resistant to
antibiotics rapidly increased. To worsen matters, resistant strains of bacteria can pass on this
resistance to other strains through bacterial conjugation and some strains are resistance to many
types of antibiotics. (BioNinja, 2017).
There is a possibility that different strains of bacteria have different degrees of resistance to
antibiotics.
References
BioNinja. (2017). Antibiotic Resistance. [online] Available at: http://ib.bioninja.com.au/standard-
level/topic-5-evolution-and-biodi/52-natural-selection/antibiotic-resistance.html [Accessed 23 Nov.
2017].
, The45Girl
BioNinja. (2017). Antibiotics. [online] Available at: http://ib.bioninja.com.au/standard-level/topic-6-
human-physiology/63-defence-against-infectio/antibiotics.html [Accessed 23 Nov. 2017].
Hypothesis
If the antibiotics are applied on different strains of bacteria, then their effectiveness will be altered
because different bacteria have different degrees of resistance to different antibiotics.
Variables
Independent variable:
The type of antibiotic.
The antibiotics used are:
A.P. or Ampicilin (represented by the colour grey on the multidisc).
C. or Chloramphenicol (represented by the colour green on the multidisc).
P.G. or Penicilin G. (represented by the colour pink on the multidisc).
S. or Streptomycin (represented by the colour white on the multidisc).
S.T. or Sulphatriad (represented by the colour mauve on the multidisc).
T. or Tetracycline (represented by the colour brown on the multidisc).
Dependent variable:
The effectiveness of the antibiotics.
This will be determined by the diameter of the zone of inhibition (mm). This will be measured
with a 30 cm ruler with an uncertainty of ±1 mm.
