Topics: Sodium chloride, Water, Plasmolysis Pages: 3 (656 words) Published: May 22, 2013


MLT1 Lab 9

Performed at Home

Microbial Growth

There are three types of environments in which cells are located which include isotonic, hypotonic and hypertonic. In an isotonic environment, the amount of water and solute are the same both inside and outside of the cell. As water drifts into the a cell, the same amount flows out creating a balanced environment both inside and outside of the cell. When there is a high level of water on the outside of the cell and a high amount of solute inside the cell, water will be drawn inside of the cell creating a hypotonic solution. The increase in water inside the cell causes the cell to become engorged and erupt. In a hypertonic environment, water will leave the cell, as the amount of water in the cell is higher than that outside of the cell. As a cell looses water in a hypertonic environment it becomes smaller in size and withers. Isotonic environments are preferred by most microbes for the most advantageous growth, although some live in slightly hypotonic solutions. (Alonzo, 2008) Growth in NaCl Solutions

Samples of S. cerevisiae and S. epidermidis were placed into sodium chloride (NaCl) solutions of 1, 7 and 15 percent which were supplied in the lab kit. The S. cerevisiae results are as follows. After 24 hours of observation there was a moderate amount of growth in the 1% NaCl solution which had a cloudy overall appearance and the growth appeared to be even throughout the specimen. There was minimal growth in the 7% NaCl solution and most of that growth was adhering to the sidewall of the tube. No growth was observed in the 15% NaCl solution. The results of the S. epidermidis specimens were very similar to those of S. cerevisiae. In the 1% NaCl solution a large amount of growth was noted. This specimen was not as cloudy as that of the S. cerevisiae but growth was consistent throughout the tube. Moderate growth was noted in the 7% NaCl...
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