Nutritional Sources and Salinity

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In the laboratory, Serratia marcescens was utilized to test Growth and Prodigiosin production under various environmental factors. The environmental conditions were temperature, pH, oxygen availability, nutritional sources, and salinity. The temperatures tested were 4 degrees Celsius, 25 degrees Celsius, and 65 degrees Celsius, and the pH values were (3, 7, 11). The carbon source was maltose and glucose. The salinity measurements consisted of 0.1% NaCl, 1.0% NaCl, and 3.0% NaCl. Lastly, the oxygen requirement was tested by using two groups, one group was tested using aeration (shaking), and one group was tested with no aeration (no shaking). The results indicate that optimal growth was experienced at a temperature of 65 degrees Celsius, a pH of 7, NaCl concentration of 0.1% and no aeration. Prodigiosin production was affected under most of the same conditions, for example, it experienced optimal growth at a temperature of 65 degrees Celsius, a pH of 7, and the same carbon source. However, results differ because Prodigiosin production experiences a higher rate at a salt concentration of 3% NaCl, and, under conditions of no aeration.


Serratia marcescens is a pathogenic bacterium that invades humans and mimics the red color of blood making it hard to detect. S. marcescens was once considered a harmless saprophyte, which is a type of microorganism that lives on dead or decaying organic matter. However, S. marcescens is now recognized as a significant opportunistic pathogen which has a tendency to create healthcare related infection and antimicrobial resistance (Herra and Falkiner 1984). Prodigiosin is an antifungal red pigment produced by S. marcescens, it holds antibacterial, antimalarial, and antifungal activities, however, it is used primarily as a biochemical tool (NCBI 2014).

Although bacteria are highly adaptable in nature, which is why they are found in nearly every place on earth, certain environmental conditions affect optimal growth for different types of bacteria. For instance, most disease-causing bacteria thrive in warm temperatures, which is why the human body provides an ideal environment for many types of bacteria to grow. On the other hand, some bacteria are able to survive in freezing temperatures of 5 degrees Celsius, yet other types of bacteria would not survive in temperatures below 60 degrees Celsius (Wagner 2008). In another way, optimal growth of bacteria is affected by pH. pH is used to classify the hydrogen ion concentration in a solution, pH values range from 1.0 (very acidic) to 14.0 (very basic). Most bacterium grow best around a neutral pH value (7). However, some bacteria thrive in very basic conditions, yet some can tolerate a pH of 1.0 (Blamire 2000).

Carbon sources also play a significant role in the growth of bacteria. Carbon is known as the structural backbone of organic compounds, and each carbon source may support different bacterial growth rates. Salinity is the amount of salt dissolved in an amount of water, the percent of sodium chloride present in the solution used for this lab accounts for the salinity.

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