Transcript ecotoxicology - Isis Tassinari

ECOTOXICOLOGY
A RESEARCH ABOUT THE TOXICITY OF THE
VIPAVA RIVER WITH BIOLUMINESCENT BACTERIA
VIBRIO FISCHERI
Authors: Nina, Tina, Francesco, Agostino
THEORY
• Ecotoxicology
is a study of the effect of toxic
chemicals on biological organisms. It’s interdisciplinary field
between ecology and toxicology.
• The Organization of economic cooperation and development
(OECD) has guidelines to the specific tests which measure
toxicity levels in organisms.
• The most important acute toxicity test is called LC50 – it is
quantity of some substance that is fatal for 50% of tested
population. The tests are usually performed on mice, other
rodents and bees.
• The most important chronic toxicity test is EC50 – this is
quantity of some substance that causes adverse affects on
50% of tested population.
VIBRIO FISCHERI
• Vibrio fischeri is a bacterium, found in marine
environments. It has bioluminescent properties. It is a
heterotrophe.
• It is found in all oceans of the world. The are found in
higher concentrations in symbiosis with certain deep sea
life withing special light organs.
• The bioluminescence is caused by transcription of the
Lux operon, indected by population dependent a quorum
sensing. The luminescence is seen only in unpolluted
environment.
VIBRIO FISCHERI
• Lux operon is a functional unit of DNA that is controlled by
single promotor. It controls light production.
• Quorum sensing is a system of simulae and response
correlated to population density.
• A heterotrophe is an organism that uses organic carbon
for growth.
• Symbiosis is cooperation between two or more organisms
(of different spieces).
HYPOTHESIS
• The water at the spring of the Vipava river is less polluted
than the water in Miren village, because human activity has
not affected it yet.
• The water at the spring of the Vipava river is more suitable
for the living environment of Vibrio Fischeri bacteria than
the water near Miren village.
METHODS
• Equipment used:
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electronic pH meter
scale
magnetic stirrer and magnet
spectrophotometer and
computer
• test tubes
• pipettes
• cuvettes
• Reagents used:
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Water samples 1 & 2
NaCl
NaOH (0,1M)
HCl (0,1M)
K2Cr2O7
METHODS
• Procedure:
• Sampling at two different parts of the Vipava river. Once at
the spring and second time at the lower part of the river (in
village called Miren). Each time, three samples were taken.
• Adjusting pH and salinity of the samples in the
laboratory in order to prepare optimal living conditions for
the bacteria.
• Activating (unfreezing) the bacteria.
• Preparing solutions for measuring the luminescence with
spectrophotometer.
• Spectrophotometry.
RESULTS
INHIBITION AFTER 15 MINUTES
INHIBITION AFTER 30 MINUTES
CONCLUSIONS
• Our toxicity test was valid.
• The first sample was less polluted/toxic and appropriate for
the growth of the bacteria. Surprisingly, the bacteria felt
better in the 1st sample than in the blank one.
• The bacteria emitted even more light when they were in the
1st sample therefore the inhibition was negative (nearly
zero). That means that the bacteria felt really good in the
new environment.
CONCLUSIONS
• The second sample was heavily polluted and inappropriate
for the growth of the bacteria.
• After the bacteria were exposed to our sample for 15
minutes, the emmission of the light decreased for 33% that means that 33% of the bacteria were inhibited (they
died or did not feel well)
• After 30 minutes the bacteria emitted 37% less light than
in the blank sample. The percentage didn’t increase very
much, because the bacteria adjusted to the new conditions.
• Both hypothesis were confirmed.