Common Microorganisms

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Common Microorganisms

By | August 2002
Page 1 of 4
INTRODUCTION

Microorganisms such as bacteria, fungus, mold, and yeast are present and common in almost every environment on earth. The normally microscopic organisms can easily be seen using differing types of agar, which creates an ideal environment for the organisms to form colonies, which are groups of hundreds of organisms that can be seen with the naked eye. In order to see individual microorganisms, it is necessary to use the magnification of a high-powered microscope. These techniques of microbiology are used in the following five experiments. The first experiment used Trypticase Soy Nutrient Agar (TSA), which can grow a wide variety of organisms and contains casein and soybean meal and a minute NaCl, to study the effectiveness of alcohol as a skin antiseptic. The second experiment tested the effectiveness of different kinds of mouthwashes as antiseptics using TSA as well. Experiment number three explored the normal human flora existing on skin and in nasal cavities, and two types of agar were used, including TSA and Mannitol Salt Agar, which contains manitol sugar, phenol red, and 7.5% NaCl. Mannitol Salt Agar tests for the presence of staphylococci bacteria that can survive in the salt that inhibits the growth of most other bacteria. Some forms of staph bacteria ferment mannitol and produce a yellow color around the colonies, which can easily be seen against the red background. The fourth experiment studied the number of bacteria in a diluted sample of uncooked hamburger meat using nutrient agar and a Quebec counter to count the colonies. The final experiment involved the growth of yeast cells under aerobic and anaerobic conditions.

MATERIALS
- Trypticase Soy Nutrient Agar
-Mannitol Salt Agar
-Sterile alcohol swab
-Listerine mouthwash
-Tubes of nutrient agar
-Diluted hamburger meat
-Quebec colony counter
-Apple juice
-Anaerobic yeast culture
-Hemacytometer
-Iodine
METHODS
Experiment 1. Effectiveness of alcohol as an...