The purpose of this experiment is to obtain isolation of individual species of particles from the mixed culture. This is completed through the isolation technique of streak plate. The objective of this experiment is to replicate the technique of streak plate but on a much larger scale. Because it is on a larger scale the particles are able to be visually observed as they are isolated using the streaking technique as the experiment is conducted. The benefits of the streaking technique is when a cultures has multiple species they are able to be more easily identified once they have been isolated.
This experiment is much like the experiments completed on an agar plate but on one a much larger scale and where techniques can be perfected before the use of agar plates and specimens are used. Because this experiment uses materials that represent those used in the streaking on agar plates the ability to simulate the events that occur when streaking is similar and allows for visualization instantly. In this experiment materials will be gathered that are representative of the tools need to complete the actual experiment of agar plate streaking.
The techniques used will be the same however the items that are used will be on a much larger scale. In replacement of flaming a loop the use of particle remover or water will be used to clean the utensils The end result of the experiment will show the isolation of the particles and degrees in consistency Materials & Methods- The materials used in the lab were collected as seen in Picture 1. For this lab multicolored sprinkles were used to represent small particles. Because of the variation in color these particles used created a mixed culture and therefore are it was not a pure culture.
Ketchup was used for a medium and was mixed with the with the sprinkles to create a culture and was contained in a square tupperware to represent a culture tube. A spoon was used a a streak utensil and was cleansed using a cup of water as a particle remover. The spoon was cleansed between streaking using the particle remover. A disposable paper plate was used as the spreading surface. In preparation for this lab the above materials were collected and the particles where mixed into medium, as seen in picture 2. The clean spoon which which represents the sterile loop for this lab was used to collect a sample of the mixed culture.
The clean spoon or streaking utensil was held like a pencil while the tupperware dish (which represents the culture tube) was held at an angle as if to prevent from contaminating the culture from airborne microbes. The streaking utensil was held still as the tupperware dish was moved and the streaking utensil tip was dipped into and out of the mixed culture. Then the culture that was obtained on the streaking utensil was then streaked onto the paper plate or spreading surface using a back and forth motion, as seen in picture 3. Resulting in a larger area of more concentrated particles.
The streaking utensil was then cleaned using the cup of water which represents the particle remover, as seen in picture 4. The streaking surface was then rotated 90 degrees. Using a cleaned streaking utensil the second streak was made from the middle of the of the first streak in a back and forth motion, as seen in picture picture 5. This streak significantly decreased the constancy of the particles from streak one. The streaking utensil was then cleaned the particle remover, as seen in picture 4. The streaking surface was then rotated 90 degrees.
Using a cleaned streaking utensil the third streak was made from the middle of the of the second streak in a back and forth motion, as seen in picture picture 6. The third streak further decreased the consistency even further spreading out the individual particles. The streaking utensil was then cleaned using the particle remover, as seen in picture 4. The streaking surface was then rotated 90 degrees. Using a cleaned streaking utensil the fourth streak was made from the middle of the of the third streak in a back and forth motion, as seen in picture picture
7. The particles were even more narrowed down in this final streak allowing for further separation of each individual particle. The streaking utensil was cleaned using the particle remover and returned to the utensil storage area. And the other items collected for this lab were cleaned and returned to their storage areas. Results- The particles that were collected for the lab were very concentrated prior to being mixed into the medium. Once the particles where mixed into the medium they was a decreased in their concentration as the medium allowed for separation by filling the spaces between them.
Once the first streak was made it was slightly less concentrated and this allowed for the particles to be spread out over the surface. The concentration of particles that were spread with each streak continued to decrease. In the final streak, as seen in picture 7, the particles were separated almost to the point of being able to individually identify each color of particle. Much as the same results that you might see with a mixed culture that was completed in a lab and final results reviewed under a microscope.
Discussion- The conclusion that was made from this experiment was that as the streaking is completed the consistency as well as the concentration degrees allowing for a more accurate identification of the individual particles. The results lead me to this conclusion because as the streaks were completed the concentration of the particles as well as the consistency of the medium decreased allowing for the individual identification of the colored sprinkles based on their color. Several attempts were made at this experiment prior to coming to the final results represented in the pictures below.
The first error that was made was not completely reading the instructions to this lab prior to the first attempt. See that several things would need to be collected to simulate a streaking experiment the materials that were used in the first attempt did not match the materials needed to complete this experiment. One the first attempt at this experiment the medium was not mixed with the particles. But separately applied to the streaking surface first the medium was applied and then the particles of rise were attempted to be streaked through the medium that was applied to the plate.
After desired results were not obtained the instructions for the experiment were reviewed to reveal the wrong materials were used and they were used in the wrong ways. The second attempt at this experiment was with cheerios in place of the sprinkles. This experiment failed because the particles as they sat in the medium began to breakdown from absorption of water from the medium. This caused the particles to be too soft for streaking and obtaining the desired results of this experiment. On the third attempt the sprinkles were used but the wrong technique was used during streaking.
The streaking surface was not rotated 90 degrees. Since the streaking surface was not rotated the back and forth motion used in the experiment was done more on the diagonal and some streaks began to touch each other. Another error that was made during this experiment was that the first streak was applied to the streaking surface without use of the back and forth motion and the pressure applied to the streaking utensil was took strong that the particles were not evenly spread out but yet more to one side of the streak.
Causing the third streak to contain no particles. Improvements that could be made to this experiment include better review of instructions prior to starting the experiment. And more practice in order to perfect the art of streaking. But, more information could be drawn from this experiment in the future including counting the particles that were transferred in each streak. For example a log could be made of the number of each color of particle in the first streak, second streak and so on.
How does this simulate exercise 1-4 and what are the differences? One of the major differences between this experiment and that completed in lab 1-4 is the use of broth culture verses medium culture. Another difference is the use of flaming verse particle cleaner. Another notable difference is the ascetic technique while we did attempt to perform these labs as they would be in a laboratory with real instruments there was no use of gloves no true concern that the culture obtained would contaminate the counter top in which the experiment was performed. And with the experiments in 4-1 there was already a pure culture existing and you are starting a new pure culture.
1. Leboffe, Michael J. and Pierce, Burton E. (2012). Breif Microbiology Laboratory Theory and application Second Edition, Common Aseptic Transfers and Inoculation Methods (pp. 26-38). Englewood, CO: Morton Publishing. 2. Leboffe, Michael J. and Pierce, Burton E. (2012). Breif Microbiology Laboratory Theory and application Second Edition, Streak Plate Methods of Isolation (pp. 39-44). Englewood, CO: Morton Publishing.