1. Kaddijatou Jallow , Ali Eastman Oku
Faculty Mentor: Dr. Dorothy Wrigley
Minnesota State University, Mankato, Department of Biological Sciences.
Streptomyces and Bacillus Tolerance to Alkaline Conditions and Production of Calcite
Introduction
Special thanks to Dr. Dorothy Wrigley for mentoring us and allowing us to use
her lab during this research and also to the Undergraduate Research Center for
sponsoring the research.
Conclusions
Results
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.
Concrete is a major construction material consisting of Portland
cement, gravel/crushed stone, sand and water [3]. Concrete is prone to
damage (cracks) from water and these damages have been shown to
expand and worsen if not repaired immediately and properly. Some
bacteria have the ability to precipitate Calcium Carbonate/Calcite
(CaCO3) when placed in the right environmental conditions with
available resources and nutrients. This project focused on discovering
the best environmental conditions in which three strains of bacteria
could produce optimum amounts of calcite. Since the pH of concrete
is relatively alkaline, it is important that the calcite-precipitating
bacteria tolerates and maintains an alkaline environment. The three
calcite-forming bacteria used were Streptomyces 1, Streptomyces 2
and Bacillus 1.
Picture 1: Microscopic picture of bacteria and calcite precipitation
The glucose traditionally used in B4 lead to a more acidic pH. Peptone
based B4 cultures become more acidic but not as acidic as glucose based
B4 media. However , media with higher amounts of peptone media were
more alkaline . The liquid conditions described above lead to very low
precipitation of calcite in peptone and slightly higher precipitation in
glucose. The organisms were very filamentous and difficult to observe on
a plate culture. Finally, the calcium concentration in the B4 media may
be the limiting factor in the quantity of calcite formed. In conclusion, a
different media and buffer system would be required to keep the media
environment alkaline and increase calcite precipitation.
Methods
The three bacteria were cultured in different media and carefully
monitored. Bacterial growth, pH change and amount of calcite
deposited in the media were monitored. Bacterial growth was initially
monitored by measuring the turbidity of the media but was later
measured through plate count. Calcite production was measured by
passing the bacteria through a filter paper. The filter paper was dried
and weighed. The amount of calcite deposited was monitored by
calculating the change in mass of the dry filter paper. B4 media was
used for the majority of the experiment with variable sources and
concentrations of energy, amino acids, and calcium (needed for
calcite). These variable sources of energy, amino acids and calcium
utilized were glucose, yeast extract, calcium chloride, calcium
acetate, TRIS and peptone.
• Achal, V., & Pan, X. (2011). Characterization of urease and carbonic anhydrase
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• De Muynck, W., Verbenken, K., De Belie, N., & Verstraete, W. (2010). Influence
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• De Muynck, W., De Belie, N., & Verstraete W (2010). Microbial carbonate
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References
Acknowledgement