Planning an experiment into the effect of mouthwash on bacteria

A2 Investigation Draft Plan (2010-2011)

RESEARCH AND RATIONALE

Aims:

To find out the effect of different brands of mouthwashes on microbes.
Comparing the efficiency of a range of anti microbials in mouthwash on the microbes and which works better than the others.

Theory:

Growth of microbes

Bacterial growth is the division of one bacterium into two daughter cells, which are genetically identical to the original cell and refers to the number of cells. There are different factors that influence the growth of microbes and this is due to specific enzymes. Each of these enzymes function best when in the presence of the optimal environmental conditions of temperature, pH, oxygen, redox potential and osmotic pressure and these increase the growth rate of microbes. Microbes obtain almost all their nutrients in solution of surrounding water and in addition, the presence of the listed factors increases this growth.

Prevention of growth of microbes

The control of microbial growth is important in the prevention of microbe development and is affected in two ways, by killing microorganisms or by inhibiting the growth of microorganisms. The control of the growth usually involves physical or chemical agents, which either kill or prevent the growth and are referred to as static agents.

Enzymes and Inhibition

In the presence of enzymes, living cells rapidly carry out many biochemical reactions. All enzymes consist of globular proteins, which have the ability to increase the biochemical reactions. In the mouth, there is an enzyme called salivary amylase, which breaks down and turns starch into a sugar called maltose.

If enzyme reactions inside the cell were to continue without regulation, there would be many problems. Cells possess regulatory chemicals, which slow down or stop enzyme catalysed reactions and are called inhibitors. The inhibitors are able to bind to the active site and leave after a time without any product forming. The enzymic reaction is reduced because while the inhibitor is in the active site, no substrate can enter. Substrate molecules compete for the active site so the rate of reaction decreases as the higher the proportion of competitive inhibitor the slower the rate of reaction.