Ben,+Y-Lynn+and+Natasha

__How do saturated salt and sugar solutions affect the rate of bacterial growth?__

Aim: To find out which (saturated) solution, salt or sugar, is the most effective bacteria killer.

Independent variable: Type of solution. Dependent variable: Size of bacteria colonies (measured in percent)

__Background__ Originally, our group was inspired by an age-old remedy: gargling salt water or eating honey will cure a sore throat. Supposedly, the concentrated amounts of sugar and salt kill any bacteria residing in your throat, alleviating ones pain and discomfort. This is linked to two processes, osmosis and diffusion.

Diffusion is a molecular process where solute particles (dissolved in a solvent) travel from an area of high concentration to an area of low concentration, which basically means that particles evenly spread themselves out until they reach a dynamic equilibrium, and a difference in concentrations no longer exists.

During osmosis, water molecules travel through a selectively permeable membrane (such as a cell's) from a **hypotonic** solution to a **hypertonic** solution. In other words, water molecules travel through a membrane from an area with a relatively **low** concentration of solute and a **high** concentration of water molecules to an area with a relatively **high** concentration of solute and a **low** concentration of water molecules.

When a cell is placed in a hypertonic solution (relative to the inside of the cell), osmosis causes the water inside the cell to diffuse outward in attempt to reach dynamic equilibrium. As water diffuses out of it, the cell shrivels up and eventually dies. This might be the reason why bacteria infecting the throat die when exposed to saturated solutions of salt and sugar.

__Materials__
 * Saturated salt solution
 * Saturated sugar solution
 * A microscope with an awesome computer interface
 * Three cultures of bacteria from a similar source

__Procedure__
 * 1) Grow one bacterial colony from each culture, in separate petri dishes (Friday)
 * 2) Prepare the saturated solutions (Tuesday)
 * 3) Coat bacteria colonies in the solutions (Tuesday)
 * 4) Take pictures, record observations over a period of four days.
 * 5) Clean up workstation

How to streak and innoculate plates: http://polymer.bu.edu/ogaf/html/chp51exp2.htm Alternate procedure that might work with tweaking: **http://secure.sciencecompany.com/Bacteria-Growing-Experiments-in-Petri-Dishes-W54C659.aspx** Scroll down to experiment Three

__Results__ Area (in %) covered by bacteria colonies over a three-day period || Day 1 || Day 2 || Day 3 || Salt || 2.3 || 1.5 || Waiting on Natasha || Sugar || 6.2 || 1.7 || “ || Water || 19 || 19 || “ ||
 * = Type of Solution = ||||||