Though the calculated means of diameter of the inhibition zone is greater with Chlorhexidine, it is not a definite indicator that verifies that Chlorhexidine is a more effective antiseptic than Tea Tree oil.
Reasons that may have lead to a greater mean, (of the diameter of the zone of inhibition) was probably due to the structure of the Chlorhexidine including its small size and more polar groups relative to the large tea tree oil molecules.
This gave Chlorhexidine an advantage in terms of faster rate of diffusion to the bacteria plasma membrane- and thus destroying the cells at a faster rate.
Considering the calculated mean, the value for T, and the scientific theory, I will accept the null hypothesises (stating that : There is no significant difference between the effectiveness of Chlorhexidine and Tea Tree oil on both B. Subtilis and E-Coli); however, still appreciating that Chlorhexidine works more faster than Tea Tree oil; and thus can inhibit bacterial growth at a marginal rate than TTO.
Susceptibility of E-Coli and B. Subtilis
Comparison Between E-Coli and B. Subtilis with Chlorhexidine:
Experimental hypothesis: B.Subtilis is significantly more susceptible to Chlorhexidine than E-Coli.
Null Hypothesis: Both B. Subtilis and E-Coli are essentially equal in terms of susceptibility to Chlorhexidine.
In the comparison between E--coli and B.subtilis on Chlorhexidine, the value I obtained for T was 2.38. This value is above the critical value for T (2.14); hence suggests that the experimental hypothesis, stating that B.Subtilis is significantly more susceptible to Chlorhexidine than E-Coli.
I will accept this experimental hypothesis due to the underlying theory of bacterial cell walls and also due to the value for T which both support this hypothesis.
This can be explained by the cell wall difference:
When B. Subtilis is flooded with crystal violet the cell walls of this bacteria retain the purple colour (such bacteria is called Gram positive bacteria). This is due to the structure of the cell wall- consisting of several layers of murein/ peptidoglcan.
Unlike B. Subtilis (gram positive), E-coli does nor retain the crystal violet dye due to a further barrier surrounding the much thinner murein layer of the cell wall.
This further barrier is an outer membrane consisting of lioppolysaccharides, presenting a physical barrier to anti-bacterial agents such as antiseptics! (the reasons for the smaller zone of inhibition on B.Subtilis) And this is what reduces the susceptibility of the gram negative E-Coli significantly.
Comparison Between E-Coli and B. Subtilis with Tea Tree Oil :
Experimental hypothesis: B.Subtilis is significantly more susceptible to Tea Tree Oil than E-Coli.
Null Hypothesis: Both B. Subtilis and E-Coli are essentially equal in terms of susceptibility to Tea Tree Oil.
In the comparison between E--coli and B.subtilis on Tea Tree Oil, the value I obtained for T was 1.45. This value is below the critical value for T (2.14); hence suggests that the null hypothesis,(stating that both B.Subtilis and E-coli are essentially equal in terms of susceptibility to Tea Tree Oil), is correct.
I believe this is due to the non-polar properties of Tea tree oil, which allows it to penetrate through the non-polar outer membrane of the gram-negative bacteria (made of lip polysaccharides)- and thus able to reach phosphoric bilayer of the gram negative bacteria at the same rate that it reaches the plama membrane bilayer of the gram positive bacteria, and then cause plasma membrane disruption.
I will therefore accept the null-hypothesis; however appreciating that the effect of antiseptics on bacteria does depend on the polarity of the molecule and whether or not it is working on a gram negative or gram positive bacteria.
I will now consider the Mechanism of action of Both Chlorhexidine and Tea Tree Oil:
Conclusions/ Points learnt (if mechanism of action is the same for the antiseptics):
