Bacteria And Sterilization Essay, Research Paper

In a classroom lab situation, as with hospitals, research centers, and other lab research areas, accurate measurements and observed results are desired. In order to obtain this objective while observing a desired organism, the specific organism must be isolated and placed into a sterile medium to ?exclude unwanted or contaminant organisms.?1

Many different techniques are useful to sterilize the culture media in the lab procedure, depending on the state and size of the medium. A popular sterilization of liquid media is through heat. If the liquid is placed in a pressure cooker-like device called an autoclave2, after approximately 15 or 20 minutes of sterilization at 1210 C all microorganisms, as well as those stubborn endospores, will have been killed. Therefore, the medium is left sterile to receive the desired organism.

Although not as effective or accurate as heat, filters also work well to sterilize heat-sensitive liquids. The liquid passes through the tiny-pored filter paper while the unwanted microorganisms become caught in the paper due to their large size. However, size plays a part in the inaccuracy of this procedure because some bacteria may be smaller than the pore size, and thus be added to the ?sterile? liquid. Therefore, although still helpful, ?sterilization by filtration is not as certain as sterilization by heat.?2

Closures are an inexpensive and easy-to-handle way of liquid medium sterilization. Cotton, plastic foam, screw caps, metal caps, and plastic caps are the popular forms of closures. One of these materials is pushed into or screwed on the top of a test tube containing the medium. With the cotton and foam plug, air is allowed to travel in and out of the tube while microorganisms are not. The caps are an advantage because of their firm, non-fraying material, despite their lack to permit the passage of air in and out of the tube.3

Solid media can be sterilized best through the use of heat. Slides, inoculation loops, and other lab materials can be treated to wet heat (autoclaving) or dry heat.4 Heat or liquid sensitive media can be sterilized using gas, as was done in the inoculation lab last week. The intense heat of the flame incinerates the object and kills off any existing unwanted microorganisms. Sterilized lab instruments must be handled by equally sterilized hands.

A sterile environment is mandatory while working with microbes because sterilized material is crucial to accurate results, and accurate results are so crucial to a successful lab.

4 Basic Microbiology (pg. 92-93)

Aseptic technique, according to the Basic Microbiology textbook definition, is ?the procedure used in handling cultures, media, and equipment so that only the desired organisms (if any) are present, with no contaminants.?1 This technique is performed to prevent contaminating or unwanted organisms from entering the sterile environment of the lab. The aseptic technique involves many suggested procedures to keep the lab environment as sterile as possible.

Many microorganisms, contaminating or not, travel in the air and possibly into bacteria being observed, if the observer (student) is not careful. Containers should be closed securely when not taken from or added to. This prevents harmful organisms in that air to expose the medium. Dust and air currents also add to the failure of an accurate lab result, if one is not careful.2

As in last week?s inoculation lab, an inoculating loop is sterilized via gas incineration and then used in the ?aseptic transfer of a (solid) culture from one tube of medium to another.?3 The transfer of a liquid culture is performed by using a sterile (before and after use) pipette.

Petri plates, as with the other containers, should be kept securely closed as often as possible, and opened just enough when needed. Creation of mist or droplets is harmful to a culture medium and its possible contamination. Long-term air exposure and misting should be avoided at all costs to perform a truly successful lab procedure.3

Therefore, aseptic technique is a lab procedure that holds an objective of isolating the desired organism throughout the lab, and to prevent contamination to the organism with a sterile lab environment.