It
is the
tension 
between creativity and skepticism that has produced the stunning
and unexpected
findings of science. —Carl Sagan
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There may be an
increasing trend present in figure 1, but the trend, if it existed, was not
obvious enough to negate the possibility of it being induced by experimental
errors, as the error bars included almost the whole trend into its range,
especially at the control and at the 40-minute sonication. We cannot
definitively say that there was an increasing trend in this graph at this point
in time. Additional tests have to be done to confirm or reject this trend, since
we did not repeat this test due to time constraints. Assuming that in
figure 1 there was no increase in bacteria growth as sonication time increases,
then there was no synergistic effect that can be seen from figure 3. Ultrasound
did not help in the inhibition of the bacteria E.
coli DH5α. However, from the results that we’ve received, we can make
no definitive conclusion. However, if the
trend did in fact exist after additional testing, we can make the following
speculations: Since it was already
known that ultrasound enhances the transport of small molecules across polymer
membranes, the slight general increase of bacteria growth as sonication time
increases may be attributed to the increased permeation rate of nutrients into
the bacteria, speeding up its metabolism so that it can reproduce at a faster
rate. We hypothesized
previously that the application of ultrasound would increase the effectiveness
of antibiotics due to the enhanced permeation rate of the cell membrane. Figure
3 suggests that, if there was indeed an increasing trend in figure 1, then there
was a synergistic effect produced by the ultrasound and spectinomycin on E.
coli. Notice figure 1, where ultrasound slightly enhanced bacterial growth.
Notice figure 2, where when antibiotic concentration is lower than 32μg/mL,
there was a gradual decrease in bacterial growth. But figure 3 exhibited no
gradual increase in bacterial growth as sonication time increased, confirming
that the antibiotic did help in inhibiting bacteria more as time increased.
Figure 3 also showed no decrease in bacteria growth, initially suggesting that
the ultrasound had no effect on the bacterial growth/inhibition. This is
unlikely, considering that in figure 1 the presence of ultrasound has already
demonstrated to be enhancing bacterial growth. This can only mean that as
sonication time increased, the effectiveness of the antibiotic in inhibiting the
bacteria also increased. Therefore, if figure 1 did in fact exhibit an
increasing trend in bacteria growth, we can speculate that the
ultrasound-induced greater rate of bacterial growth had reached equilibrium with
the ultrasound-enhanced antibiotic action, producing an overall trend of
constant bacterial growth as sonication time increases. The exact mechanism
of action of ultrasound complementing antibiotics against bacteria is not known,
but we can make three postulates. We firstly propose the pores on the cell
membrane will be set into oscillatory motion by the pressure of the ultrasound.
When the pores open, antibiotics will be able to go through them more easily,
disabling the ribosomes within. We further postulate that it is possible for ultrasound to induce more energy into the antibiotic molecules than they originally possessed, and according to the Kinetic Molecular Theory (KMT), increasing the speed that these molecules are moving at, increasing the frequency at which they come into contact with the bacteria, and thus gaining a higher probability of permeating into the cell, reaching the MIC inside the cell in a given period of time.
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Enhancement of Antibiotic Action with an Application of
Ultrasound 01/05/2007 |
