Emma Nikols
 How does the efficiency of Bacillus subtilis and
Pseudomonas fluorescens biofilters compare
when used to prevent soil contamination?
 This experiment should take 3 weeks to carry out.
 Bacteria will be cultured and a biofilm will
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form which will be placed in a burette filled
with glass beads to simulate soil.
The contaminants will consist of copper nitrate
dissolved in distilled water and will be poured
into the burette.
The flow rate of these contaminants will be
measured.
A water quality tester will be used to measure
the amount of copper nitrate remaining in the
water after it filters through the burette.
Lower concentration  biofilm effective at
removing contaminants.
Independent Variable
 The type of bacteria used.
Dependent Variable:
 The flow rate of the contaminants
through the soil will be measured in
seconds or minutes using a stop watch.
 Concentration of contaminants using
water quality test kit in ppm
Control Group
 Trial run without any bacteria.
Factors that must remain constant
 temperature, amount of contaminants, size and
type of glass beads used, pH level of the setups,
amount of dissolved water used, size of burette,
type of water quality test kit
P. florescens
 Pseudomonas fluorescens
 Bacillus subtilis
 Glass beads to simulate
B. subtilis
soil
 Molasses medium
 Stopwatch
 3 mm glass double burette  10 g/L molasses
 0.123 g/L K2 HPO4
 2 150 mL beakers
 0.04 g/L KH2 PO4
 Contaminant – copper
nitrate dissolved in 15 mL  1 g/L NaCl
 3 g/L NaNO3
of distilled water
 2 g/L NH4 NO3
 Water quality tester to
find concentration of
 0.005 g/L yeast
contaminants
extract
 1 L distilled water
 Biofilms can potentially be used to prevent the
spread of contaminants through soil that kill plants
and animals.
 In some cases, biofilms have even been able to
neutralize contaminants such as nuclear waste.
 This could reduce many detrimental effects to
individual species and to ecosystems.
 Explains research of a wide variety of bacterial
biofilms and their possible role in bioremediation.
 Studied differences in gene expression between
different bacteria within a biofilm, in addition to
their quorum sensing communication system, and
how these relate to their ability to adapt and survive.
 Found that plasmid-mediated gene transfer occurs
because biofilms are dense and heavily populated.
 Chemotactic bacteria are discussed as an
advantageous choice due to the augmentation of
bacteria survival and degradation of contaminants.
Singh, Paul & Jain, 2006)
 Study done that investigates ability of sulphate-
reducing bacteria to reduce hexavalent chromium
and remove it from a solution as an insoluble
precipitate.
 Used pure culture of Desulfovibrio desulfuricans and
a mixed culture of sulphate-reducing bacteria, each
added to a separate biocell. Bacteria and sediment
that settled on the bottom of the cell were collected.
 It was found that 86% of the chromium was removed
by the D. desulfuricans and 88% was removed by the
mixed culture.
(Smith & Gadd, 2000).
 Researchers experimented with genetic modification of
Escherichia coli and the usage of its biofilms as an air
filter.
 Biofilter breaks down and mineralizes pesticides in air,
which converts them to safe substances. E. coli
biofilters specifically target parathion and methyl
parathion pesticides.
 Bacteria removed 95.2% of the parathion and 98.6% of
the methyl parathion from the air it was used on
 System could be improved until it has a 100% efficiency
rate. Process could potentially be applied to soil
bioremediation as well.
(Inderscience Publishers, 2011)
 It was hypothezied that P. fluorescens will be a more efficient
biofilter than Bacillus subtilis in a site contaminated with copper
nitrate. Both Bacillus subtilis and Psuedomonas fluorescens are
chemotactic and produce surfactants, meaning that they will at
least be able to survive toxic enviornments. However, B. subtilis
has been proven to be less successful at removing the
contaminants it targets than P. fluorescens (Singh, Cameotra
2004). Although B. subtilis specifically targets copper, the
contaminant being used in this experiment, P. fluroescens targets
chromium which is more difficult to reduce (Priester et al.,
2006)(Singh, Cameotra 2004). This is because chromium is a
stronger reducer and copper is more of an oxidizer when the
acitivity series of metals is taken into account. It is unknown
whether B. subtilis is able to survive better in copper, but it can be
inferred that P. fluorescens will be able to adapt to the and
decontaminate the soil due to its higher reduction ability.
Inderscience Publishers. (2011, April 14). Filtering out pesticides with genetically
modified bacteria. ScienceDaily. Retrieved September 19, 2015 from
www.sciencedaily.com/releases/2011/04/110414104211.htm
Singh, R., Paul, D., & Jain, R. K. (2006). Biofilms: implications in bioremediation.
Trends in Microbiology, 14(9), 389-397. doi:10.1016/j.tim.2006.07.001
Smith, W. L., & Gadd, G. M. (2000). Reduction and precipitation of chromate by
mixed culture sulphate-reducing bacterial biofilms. Journal of Applied
Microbiology, 88(6), 983-991.
doi:10.1046/j.1365-2672.2000.01066.x
Singh, P., & Cameotra, S. S. (2004). Enhancement of metal bioremediation by use
of microbial surfactants. Biochemical and Biophysical Research
Communications,319(2), 291-297. doi:10.1016/j.bbrc.2004.04.155