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 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

Pseudomonas fluorescens Bacillus subtilis Glass beads to simulate soil Stopwatch 3 mm glass double burette mL beakers Contaminant – copper nitrate dissolved in 15 mL of distilled water Water quality tester to find concentration of contaminants B. subtilis P. florescens Molasses medium 10 g/L molasses g/L K2 HPO g/L KH2 PO4 1 g/L NaCl 3 g/L NaNO3 2 g/L NH4 NO g/L yeast 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.

Singh, R., Paul, D., & Jain, R. K. (2006). Biofilms: implications in bioremediation. Trends in Microbiology, 14(9), doi: /j.tim 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), doi: /j x Inderscience Publishers. (2011, April 14). Filtering out pesticides with genetically modified bacteria. ScienceDaily. Retrieved September 19, 2015 from Singh, P., & Cameotra, S. S. (2004). Enhancement of metal bioremediation by use of microbial surfactants. Biochemical and Biophysical Research Communications,319(2), doi: /j.bbrc