Microbial Communities on a Salt Concentration Gradient (9C)

 

1. If you consider the series of increasingly saline solutions as a habitat gradient, how does your experiment compare with Whitaker's study of trees in the Great Smokey Mountains?
   • This experiment compares with Whitaker's study in that we measured at regular intervals along a gradient, just as Whitaker did.
2. Somewhere between no salt and the salt concentration of sea water, a freshwater protozoan will reach its tolerant limit, and the experimenter would not expect to see that species in more saline solutions. What would the Clements model predict for all the ranges of species in a microbial community sampled along this salt gradient? What would Gleason predict?
   • Clements would predict that there is no overlap between the gradients while Gleason would predict overlap, going along with his continuum theme.
3. Which model best represents your data? Explain.
   • The Gleason model best represents the data because the same species was found in different infusions.
4. If you had collected dried grass from a salt marsh near the sea as your source of culture medium and resting protozoans for this experiment, would you expect a different result from your series of infusions? Why?
   • I would expect somewhat different results because even the spring water infusion would have salt in it because of the original salty environment.
5. Early stages of hay infusions are dominated by bacteria; then protists that feed on bacteria tend to reduce bacterial populations. From the appearance and odor of your cultures, could you tell which tubes had the most robust bacterial populations? Although you cannot see bacteria well under a compound microscope, do you suspect different types may grow in different salt concentrations? Explain.
   • I could not tell which cultures had the most bacteria because I did not smell them and they generally looked the same, although the seawater had more “muck” on it than the other infusions. I would suspect that different types of bacteria grow in different salt concentrations based on personal experience wherein I used salt water to clean out new piercings to prevent bacterial infections. 
   
   
   

** Aidan Bailey and I did this lab together.