Escherichia Coli, Lab Report Example

Abstract

In this laboratory experiment, we cultured the Escherichia coli in broths of nutrients in addition to the T- 4 bacteriophage that was also contained in a nutrient broth. The hypothesis that was tested is that the mutational resistance takes placerandomly in correlation to the Escherichia coli and infection from the T- 4 phages. In order to verify that the cloned bacteria were classified as Escherichia coli, we provided a culturing of the bacteria (Luria and Delbr?ck 491). We observed the turbidity of the supernatant subsequent to its exposure to the centrifuge. The deep quality of turbidity was an indicator of the carbon dioxideproduction of  the Eschericchia coli cells.

Objective

In this laboratory experiment we facilitated the growth of a virus. The category of virus for which we facilitated development was designated as bacteriophages. The bacteriophages have the characteristics of infesting other bacteria. The specific virus that we grew is designated bacteriophage T- 4 and it was used in order to infect the bacteria Escherichia coli.  We used a special green agar that changes its hue faintly when the bacteria demonstrated signs of life.

Background

Conventionally in science, the viruses decimate animal cells that are acknowledged in the field of microbiology as eukaryotic cells. There are instances where the viruses invade prokaryotic cells. The prokaryotic cells are distinct from the eukaryotic cells that are possessed by animals in that the nucleus or the mitochondria is absent. The prokaryotic cells do not possess mitochondria due to the attribute of possessing their proprietary mitochondria that produces their energy. There are two primary categories of prokaryotesthat are archaea and bacteria. The viruses that have the trait of attacking bacteria are appropriately designated as bacteriophages. The bacteriophages only destroy bacterial cells by inserting their proprietary genetic information into the host bacteria cell Luria and Delbr?ck 496).

Transduction took place in the instance that the bacteriophage reproduced in the host cell and subsequently infested other cells. This process is designated as the lysis cycle. In certain circumstances when the bacteria receivedexposure to the bacteriophages,theEschericchia coli cells commenceddying and wer regenerated. This is contradictory with regards to what is known in reference to phages. When this phenomenon took place, the bacteria developed a resistance to the phages. The resistance took place when one of the bacterial cells acquired resistance and initiated reproduction. The cells that wereclonesdeveloped a resistance to the phages due to the attribute of having the identicalgeneticcomposition of the first resistant cell. The original culture was not composed of the resistant cells. The cells have inherited a mutation that has caused them to develop a resistance against the phage. The laboratory experiment was designed in order to observe if the Escherichia coli acquired an immunological resistance to the T-4 phage. The laboratory experiment that we conducted had been initially conducted by Max Delbr?ck and Salvador E. Luria (Luria and Delbr?ck 496). They observed that the bacteria can develop a resistance to the phages. Their outcome of work earned the 1969 Noble prize. The objective of their experiment was to ascertain that random mutations took place in the bacteria when the bacteriophages were applied.

Procedure

First Period

We diluted the diluted the phage lysate to a concentration of 10^-9. Subsequently, we acquired five testingtubesof molten top agar. We then placed labels on the agar tubes and the green agar tubes in order to distinguish them. The labels were marked 10^-7 and placed on the agar tubes. We marked the other labels 10^-10 and placed the labels on the green agar tube.  In the next step we injected 1000 µl with a pipette of each of the dilutions into the tubes that correlated with the vortex and the molten top agar. Afterwards, we poured each of the tubes of the molten top agars on the green agar plate that corresponded.  We allowedthe top agar to desiccate and solidify.  In the final step of the first period, we placed the plates in an incubator for two days at a temperature of 37° C.

Second Period

Weretrieved the incubated plates from the first period and observed for signs of growth. We observed that there was no growth of plaque. There was researcher’s error in the process of injecting the dilutions.  We were able to observe the results from the instructor’splates. The plates are demonstrated in the pictures below. We observed forty nine plaques in the plate that was labeled 10^-9(50/ 10^-9 = 5.0 x 10¹⁰ PFUs).  We applied the instructors sample in order to prepare a new phage lysate. We used a pipette with one   milliliter of the Escherichia coli culture into a novel testing tube. Afterwards, the phage was injected into the central part of the plaque and was injected in the TSB tube. We subsequently incubated the new phage culture in the TSB testing tube for a period of one day.

We acquired the phage culture and there was turbidity manifested in the sample.  We aggregated five drops of chloroform to the culture that possessed the phage culture. In the next step, we mixed the chloroform by applying a vortex. We allowed the culture and the chloroform to settle for five minutes afterwards, we used a pipette in order to inject one milliliter of culture. We applied a centrifuge for one minute. The final step was to decant the supernatant into a different tube. The color that was obtained was not milky white. The characteristicof the supernatant was light gray and turbid.

Discussion

The results that we obtained verified the hypothesis of the resistant quality of the Eschericchia coli cells taking place as a result of a mutation occurring in the genetic makeup of the bacterial cell.  In accordance with the results from Figure 1, the group that was applied a negative control showed that the first agar plate changed to a yellow/ green tint. This demonstrated the evidence of the bacteria’s growth on the plate that was labeled 10^-7. When the dilution was injected in the testing tube, the supernatant demonstrated a turbid color when we applied a centrifuge.  The turbid color was the outcome of the Eschericchia coli cells producing carbon dioxide. The turbidity in the supernatant confirms that the Escherichia coli had acquired resistance to the T- 4 bacteriophage. This was attributed to the color of the supernatant. The turbidity in the supernatant demonstrated that all of the Escherichia coli cells were not destroyed by the T- 4 bacteriophage (Luria and Delbr?ck 496).

Works Cited

Luria, Salvador and Max Delbr?ck “Mutations of bacteria from virus sensitivity to virus resistance.”Genetics 28(1943): 491- 511.