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Salinity Lab


Halobacterium salinarum (halo) is an obligatory halophile; it requires a media of very high salinity in order to survive and will not grow or will lyse in media waith to low a salinity. Thus the quality of the halo’s growth is greatly affected by the salinity of its media. The purpose of this investigation is to determine how the salinity of the halo’s media affects its growth and in what concentration it grows best.


Since the halo are thrive in very salty places they will grow best in the media with the highest salinity (4.3 M).


1. Arrange 24 test tubes into six groups for each of six salinity levels (distilled water, 2.3 M, 2.8M, 3.3M, 3.8 M, 4.3 M).
2. In each group, pipette 5mL of the corresponding concentration of medium.
3. In three of the four test tubes in each group, add 100.0 µl of Halo (NRC-1) of the same initial OD.
4. Leave the fourth test tube in each group as the control.
5. Incubate all the test tubes for 48 hours.
6. After the incubation, measure and record the cell densities of each cultures using the controls as blanks.
7. If possible, reincubate cultures for another 48 hours and repeat step 6.
8. Compare growth patterns of the Halo cultures.



After 46 hours, the Halo in the 3.3 M salinity grew the most. We know that the Halo in the 3.3 M had the most growth because it had the greatest OD average of 1.065. We think the reason why the Halo grew the most in a salinity solution of 3.3 M was because Halo reaches its growth peak more quickly and the peak is higher. Halo in the salinity solutions of 2.3 M and 2.8 M also reach their growth peak quickly, however, their peak is not so high like the growth peak of 3.3 M solution. After 46 hours, the growth of Halo in 4.3 M salinity was 3rd greatest, after 3.3 M and 3.8 M solutions. We think this was because it takes Halo in 4.3 M salinity longer for it to reach its peak than it takes when Halo is in 3.3 M and 3.8 M solutions.

After 110.5 hours, the Halo grew the most in the salinity solution of 4.3 M. We know that the Halo grew the most in 4.3 M salinity because it had the greatest OD average of 1.353. We think that Halo had the most growth in salinity of 4.3 M because Halo grows the best in high salinity conditions. The solution of 4.3 M had the greatest salinity of all samples. The salinity solution of 4.3 M also grew the most because it had the greatest/highest growth peak. The reason why Halo grew the most in the 3.3 M solution in 46 hours because it takes 3.3 M the shortest length to reach its growth peak. This means that Halo reached its growth peak in 3.3 M in 46 hours or less. However, it took 4.3 salinity 110.5 hours or less to reach its growth peak. Over the long run, 4.3 M showed the greatest growth of an average of 1.353 OD and 3.3 M was second to show 1.159 OD.

Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.

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