Bacterial Growth in the Lake Waco Wetlands in Different Nitrogen Concentrations
Kara Klott, Derek Green, Michael Terrasa; Baylor University Biology 1106
Abstract
Results
Discussion
An experiment was designed to determine if there was a correlation between bacterial growth and the
Nitrogen levels are higher in cell five than in cell one. The nitrogen test also proved the
The results for the amount of nitrogen naturally occurring in each cell (Table 1) oppose the
nitrogen levels of cell one and cell five of the Lake Waco Wetlands. Dilute, nitrogen-enriched, and
nitrogen concentrations of the dilution solutions to be almost half that of the fertilized
hypothesis; there is more nitrogen naturally present in cell five than in cell one. The hypothesis was
control solutions were created using water drawn from cell one and cell five. Nitrogen levels of each
samples (Table 1). From the incubated dilution plates, it can be seen that the greatest
based on the amount of plants in each cell; the more plants present the greater possibility of
solution were tested using a Bechman Spectrophytometer. Serial dilutions were made from each
number of bacteria grew in the most nitrogen rich population in cell five and in cell one.
nitrogen fixation, therefore, the less nitrogen available in the environment. From the literature,
solution then plated on tryptic soy agar and incubated for twenty-four hours. Colonies on each plate
Compared to cell one, cell five had more nitrogen present and a greater amount of
nutrient rich environments are actually environments that are full of life (Wu 538). There is more
were counted to calculate the concentration of bacteria in each solution. Nitrogen levels were higher
bacterial growth. Also, among the individual dilution plates the more concentrated plates
bacterial growth in nitrogen-enriched environments. This supports the hypothesis, and although
in cell five and bacterial concentrations were highest in the nitrogen-rich solutions. These results show
had greater bacterial growth. The first round of dilution plates was made after the
carbon is the main limiting factor for bacterial growth, nitrogen also plays a large role in the growth
a positive correlation between the nitrogen levels and bacteria population growth.
bacteria grew for forty-eight hours. In the second experiment, the bacteria was allowed to
of bacteria ( Wu 537).
Introduction
grow for a shorter period of time, twenty-four hours, before making the dilution plates;
In the Waco water supply, nitrogen levels are high due to fertilizer in surface runoff. The North
Bosque River filters through the Lake Waco Wetlands before entering Lake Waco and a water
treatment plant. “A considerable number of bacterial species” in the wetlands “are able to exert a
however the results were inconclusive. Then, the plates were recounted after another
Conclusion
twenty-four hours of incubation. The results were still inconclusive. Finally, a fourth trial
Results indicate more bacterial growth occurs in the nitrogen solution than incubating on
was performed and the results were similar with the first trial (Figure 1).
dilution plates. Bacteria in cell five and cell one of the wetlands grow more efficiently in
nitrogen-rich solutions (Figure 1). The experiment revealed a higher level of nitrogen present
beneficial effect upon plant growth” (Rodríguez 17). Some bacteria share a mutualistic relationship
in cell five than in cell one of the wetlands located in Waco, TX. Further observations
with plants: these nitrifying bacteria fix nitrogen in the form of ammonia to a nitrate that is usable by
Table 1. Nitrogen Concentrations in Cell One and
Cell Five
plants; “root secretions supply most of the energy in the rhizosphere, so bacterial adaptations that
help a plant thrive and secrete nutrients also help the bacteria” (Cambell 793). We hope to
Cell 5
establish a correlation between bacterial populations and nitrogen concentration, and its
Diluted
Nitrogen Rich
Control
relationship to cell one and cell five at the Lake Waco Wetlands.
Cell 1
Diluted
Nitrogen Rich
Control
Materials and Methods
growth, however, the experiment proved that nitrogen also directly effects the growth of
bacterial populations. Therefore, the preliminary research indicates that nitrogen positively
affects the growth of bacteria.
0.0087
0.018
0.0141
Using six sterile, 100ml plastic containers, separate each of the two samples into three
individual containers for a total of six. Seal each container with a lid.
Control with 60ml of wetlands water
Diluted sample with 30ml of wetland water and 30ml of deionized water
Nitrogen-rich sample with 60ml of wetland water and 1 g of nitrogen-only fertilizer
Rodríguez H., (1999), Phosphate Solubilizing Bacteria and Their Role in Plant Growth
Promotion, Biotechnology Advances, 17, 319-339.
300
300
300
Figure 1. Bacterial Population Counts from Dilution
Plates
300
•
•
•
the amount of bacterial growth. Wu (2006) states carbon is the limiting reagent for bacterial
Literature Cited
1. Obtain samples from two locations:
•
The entrance into the Wetlands from the North Bosque River (cell one)
•
The wetland exit into the Bosque River (cell five)
2.
Nitrogen Results (ABS)
0.0265
0.0553
0.0487
unveiled a positive correlation between the levels of nitrogen found in an environment and
300
•Wu Gen-Fu, (2006), Evaluation of nutrient limitation in aquatic ecosystems with nitrogen
fixing bacteria, Journal of Environmental Sciences, 18.3, 537-542.
•Campbell, Reid, Biology. San Francisco: Pearson, 2008.
250
3. Take the six samples from cell one and cell five and test the nitrogen levels using a Bechman
Spectrophytometer
Acknowledgements
4. Allow bacteria to grow for a minimum of forty-eight hours
We would like to thank Dr. Marty Harvill (Baylor University, Biology Senior Lecturer), Mrs. Nora
200
Reservior & Aquatic Systems), College of Arts and Sciences, Department of Biology, and the
180
166
Lake Waco Wetlands.
Diluted 30ml
wetlands water
30ml DI water
100
79
Fertilized 60ml
of wetlands
water 1g of
nitrogen
72
16
14
14
25
36
37
43
50
Cell 1
Cell 5
Trial 1
Cell 1
Cell 5
Trial 2
Cell 5
Trial 3
Cell 1
0
0
0
0
0
0
0
0
0
0
10^4
10^5
10^6
10^7
0
1
0
0
0
0
0
0
0
10^4
10^5
10^6
10^7
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Cell 1
10^4
10^5
10^6
10^7
10^4
10^5
10^6
10^7
10^4
10^5
10^6
10^7
10^4
10^5
10^6
10^7
0
10^4
10^5
10^6
10^7
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
0
0
0
0
1
1
5
0
0
0
0
0
0
2
0
1
Examine results
Count colonies on each individual agar plate and record results
Colony counts below 30 are labeled TFTC (too few to count) and are not used for calculations
Colony counts between 30 and 300 are used for calculations
Colony counts above 300 are labeled TNTC (too numerous to count) and are not used for
calculations
Control 60ml
wetlands water
0
1
6.
•
•
•
•
for Reservior & Aquatic Systems), Dr. Robert Dyle (Baylor University, Biology Chair/Director,
10
•
University, Biology Lab TA’s), Sara Seagraves (Baylor University, Project Assistant at the Center
150
0
•
•
Schell (Lake Waco Wetlands Director), Amanda Hartman, Anica Debelica, Frank Booc (Baylor
10^4
10^5
10^6
10^7
•
•
Make dilution plates
Take 1ml from each sample and add it to a 200ml container with 99ml of deionized water
for a 10^-2 dilution
Add 1ml from the 10^-2 dilution to another 99ml of deionized water for a 10^-4 dilution
Add 1ml of the 10^-4 dilution onto an agar plate and 0.1ml of the 10^-4 solution onto an agar
plate for a 10^-5 dilution
Add1ml from the 10^-4 dilution to another 99ml of deionized water for a 10^-6 dilution
Add 1ml of the 10^-6 dilution onto a 10^-6 agar plate and 0.1ml of the 10^-6 dilution onto
an agar plate for a 10^-7 dilution
Allow the bacterial populations to grow on the agar plates for 24 hrs in an incubator
Number of Bacteria Populations
5.
•
Cell 5
Trial 4