Mic 3
Title
Laboratory 3: Examination of Living Bacteria
Introduction
Unstained bacteria are difficult to observe because of the lack of contrast between the cells and the surrounding. To see them in an unstained state and also to observe their motility, a hanging-drop or a wet mount technique is used. A wet mount is the technique of placing small amounts of specimen in a droplet of water for viewing with the compound microscope. Motility is an inheritable phenotype and is critical for identification and classification of bacteria. The technique is done by applying petroleum jelly to all sides of a cover glass. Add a water droplet and specimen using an aseptic loop onto the concave side of a depression slide. Put the jelly side of the cover glass over the droplet. View the droplet as it is suspended or "hanging" from the side. It is a "hanging drop" slide because the droplet remains untouched due to the concave shape of the cover glass and it just hangs from the cover glass. Microscopic study of such a wet preparation can provide useful information. Primarily, the method is used to determine whether or not an organism is motile, but it also permits an undistorted view of natural patterns of cell groupings and of individual cell shape. Hanging-drop preparations can be observed for a fairly long time, because the drop does not dry up quickly. Wet-mounted preparations are used primarily to detect microbial motility rapidly. The fluid film is thinner than that of hanging-drop preparations and therefore the preparation tends to dry up more quickly, even when sealed. Although the hanging drop is the classical method for viewing unstained microorganisms, the wet mount is easier to perform and usually provides sufficient information.
Objective
To become familiar with method to examine the living bacteria.
Materials 1. 24 hours nutrient broth cultures of
a) Staphylococcus aureus
b) E. coli 2. Hollow ground depression slides 3. Inoculating loops
Laboratory 3: Examination of Living Bacteria
Introduction
Unstained bacteria are difficult to observe because of the lack of contrast between the cells and the surrounding. To see them in an unstained state and also to observe their motility, a hanging-drop or a wet mount technique is used. A wet mount is the technique of placing small amounts of specimen in a droplet of water for viewing with the compound microscope. Motility is an inheritable phenotype and is critical for identification and classification of bacteria. The technique is done by applying petroleum jelly to all sides of a cover glass. Add a water droplet and specimen using an aseptic loop onto the concave side of a depression slide. Put the jelly side of the cover glass over the droplet. View the droplet as it is suspended or "hanging" from the side. It is a "hanging drop" slide because the droplet remains untouched due to the concave shape of the cover glass and it just hangs from the cover glass. Microscopic study of such a wet preparation can provide useful information. Primarily, the method is used to determine whether or not an organism is motile, but it also permits an undistorted view of natural patterns of cell groupings and of individual cell shape. Hanging-drop preparations can be observed for a fairly long time, because the drop does not dry up quickly. Wet-mounted preparations are used primarily to detect microbial motility rapidly. The fluid film is thinner than that of hanging-drop preparations and therefore the preparation tends to dry up more quickly, even when sealed. Although the hanging drop is the classical method for viewing unstained microorganisms, the wet mount is easier to perform and usually provides sufficient information.
Objective
To become familiar with method to examine the living bacteria.
Materials 1. 24 hours nutrient broth cultures of
a) Staphylococcus aureus
b) E. coli 2. Hollow ground depression slides 3. Inoculating loops