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Sunday, February 21, 2010
Dictyostelium development and the relationship with temperature
I. Introduction
The group Mycetozoa, classified as an protozoa, includes the slime mold Dictyostelium and under certain conditions this amoebae is a useful organism that can be observed in multiple stages of development. It can develop form spores, to mature fruiting bodies that again release spores, and start the life cycle again. When the spores hatch they are called myxamoebae. Myxamoebae are eukaryotic cells, and while they feed, and mate the amoebae starts to aggregate. Aggregation is a starvation period that can last up to eight hours. During this stage of development cAMP receptors are made, phosphodiesterase inhibitors are formed, and a chemical signal is released (Gilbert, 2003). The amoebae is now shaped similar to a flatten nerve body with dendrites. The ameobiod is able to increase the cAMP gradient because of the signal and develop into the next stage of development. The amoebae next stage of development is now called a pseudoplasmodium. The pseudoplasmodium is slug like and can only move in one direction. While the slug is slinking along the agar dish, it eventually starts to settle on the posterior end, which are full of prespore cells. This stage is called transformation, but it is also nicknamed after the amoebae’s shape, a Mexican hat. During this stage of development the slime mold cells reorganize, and a tube on the top of the hat appears and secretes cellulose. Then, the prespore cells in the fruiting body migrate to the anterior, and prestalk cells migrate to the posterior and die at the fruiting body. The migration process of the two cell types takes up to ten hours to produce a mature fruiting body with a fruiting body mass, stalk, and spore mass (Gilbert, 2003). The Dictyostelium observed in the experiment were gorgeous under the microscope, and resembled a delicate tulip, with a very skinny stem, and a tightly wrapped bud. The spore mass on the anterior of the mature slime mold were now ready to release the spores and the development cycle will repeat itself.
The hypothesis of the experiment is Dictyostelium development will flourish at 37 degrees Celsius in an agar dish, rich of E. coli, and the slime mold with develop much slower at room temperature in an agar dish treated with E. coli.
II. General Procedures
The experiment was designed to test the life cycle of Dictyostelium under two different controlled temperatures and to observe how it influenced developmental stages.
In the experiment, approximately 8 pseudoplasmodium were identified and verified using a microscope. Then, the slugs where transplanted into two other Petri dishes. In the experiment a sterile loop was used, lightly passing the slime mold in a brush like motion onto the two separate Petri dishes that were labeled with initials, and temperatures. The Petri dishes both contained a nutrient agar, E. coli, and were carefully opened to prevent contamination, and to only opened to replant the slugs. Finally, one dish was placed in a controlled area at room temperature and the other dish was placed in a controlled area at 37 degrees Celsius. The Dictyostelium was observed eight times during a period of 12 school days.
III. Observations & Results
See attached observation log and drawings for addition experimental data.
IV. Discussion
The results of the experiment showed one prediction of the hypothesis was true, but the data also showed the second prediction was incorrect. The Dictyostelium that were placed in 37 degrees Celsius were observed in all stages of development, including spores, and myxamoebae. At 37 degrees Celsius the amoebae were also observed during aggregation, as a pseudoplasmodium, Mexican hat shape, in culmination, and as mature fruiting body. It appeared the slime molds were constantly developing spores and generating mature fruiting bodies and repeating the life cycle. The data concludes the cellular slime mold thrives in warm conditions, with E. coli. The life cycle in the 37 degree plate was continuous and repeating and the observations concluded that Dictyostelium enjoys hot, tropical conditions (like my grandparents), and would most likely be found in areas with this type of environment.
The pseudoplasmodium transferred into the room temperate Petri dish developed to a mature fruiting body with stalk and a spore mass. At first observation the mature fruiting bodies were in perfect condition, immobile, and resembled a pristine fossil secured in the agar. Twenty-four hours later, during the second observation the mature fruiting bodies were unchanged and the assumption is the Dictyostelium matured within the first twenty-fours hours and then died. The spore mass of the mature organism did not release spores for fertilization and the life cycle ended. The observation concluded Dictyostelium does not survive at room temperature, even though it was transferred into a nutrient agar plate with its favorite food, E. coli.
References:
Gilbert, S. F., (2003). Developmental Biology (7th ed.). Massachusetts: Sinauer Associates
Dictyostelium development and the relationship with temperature
The group Mycetozoa, classified as an protozoa, includes the slime mold Dictyostelium and under certain conditions this amoebae is a useful organism that can be observed in multiple stages of development. It can develop form spores, to mature fruiting bodies that again release spores, and start the life cycle again. When the spores hatch they are called myxamoebae. Myxamoebae are eukaryotic cells, and while they feed, and mate the amoebae starts to aggregate. Aggregation is a starvation period that can last up to eight hours. During this stage of development cAMP receptors are made, phosphodiesterase inhibitors are formed, and a chemical signal is released (Gilbert, 2003). The amoebae is now shaped similar to a flatten nerve body with dendrites. The ameobiod is able to increase the cAMP gradient because of the signal and develop into the next stage of development. The amoebae next stage of development is now called a pseudoplasmodium. The pseudoplasmodium is slug like and can only move in one direction. While the slug is slinking along the agar dish, it eventually starts to settle on the posterior end, which are full of prespore cells. This stage is called transformation, but it is also nicknamed after the amoebae’s shape, a Mexican hat. During this stage of development the slime mold cells reorganize, and a tube on the top of the hat appears and secretes cellulose. Then, the prespore cells in the fruiting body migrate to the anterior, and prestalk cells migrate to the posterior and die at the fruiting body. The migration process of the two cell types takes up to ten hours to produce a mature fruiting body with a fruiting body mass, stalk, and spore mass (Gilbert, 2003). The Dictyostelium observed in the experiment were gorgeous under the microscope, and resembled a delicate tulip, with a very skinny stem, and a tightly wrapped bud. The spore mass on the anterior of the mature slime mold were now ready to release the spores and the development cycle will repeat itself.
The hypothesis of the experiment is Dictyostelium development will flourish at 37 degrees Celsius in an agar dish, rich of E. coli, and the slime mold with develop much slower at room temperature in an agar dish treated with E. coli.
II. General Procedures
The experiment was designed to test the life cycle of Dictyostelium under two different controlled temperatures and to observe how it influenced developmental stages.
In the experiment, approximately 8 pseudoplasmodium were identified and verified using a microscope. Then, the slugs where transplanted into two other Petri dishes. In the experiment a sterile loop was used, lightly passing the slime mold in a brush like motion onto the two separate Petri dishes that were labeled with initials, and temperatures. The Petri dishes both contained a nutrient agar, E. coli, and were carefully opened to prevent contamination, and to only opened to replant the slugs. Finally, one dish was placed in a controlled area at room temperature and the other dish was placed in a controlled area at 37 degrees Celsius. The Dictyostelium was observed eight times during a period of 12 school days.
III. Observations & Results
See attached observation log and drawings for addition experimental data.
IV. Discussion
The results of the experiment showed one prediction of the hypothesis was true, but the data also showed the second prediction was incorrect. The Dictyostelium that were placed in 37 degrees Celsius were observed in all stages of development, including spores, and myxamoebae. At 37 degrees Celsius the amoebae were also observed during aggregation, as a pseudoplasmodium, Mexican hat shape, in culmination, and as mature fruiting body. It appeared the slime molds were constantly developing spores and generating mature fruiting bodies and repeating the life cycle. The data concludes the cellular slime mold thrives in warm conditions, with E. coli. The life cycle in the 37 degree plate was continuous and repeating and the observations concluded that Dictyostelium enjoys hot, tropical conditions (like my grandparents), and would most likely be found in areas with this type of environment.
The pseudoplasmodium transferred into the room temperate Petri dish developed to a mature fruiting body with stalk and a spore mass. At first observation the mature fruiting bodies were in perfect condition, immobile, and resembled a pristine fossil secured in the agar. Twenty-four hours later, during the second observation the mature fruiting bodies were unchanged and the assumption is the Dictyostelium matured within the first twenty-fours hours and then died. The spore mass of the mature organism did not release spores for fertilization and the life cycle ended. The observation concluded Dictyostelium does not survive at room temperature, even though it was transferred into a nutrient agar plate with its favorite food, E. coli.
References:
Gilbert, S. F., (2003). Developmental Biology (7th ed.). Massachusetts: Sinauer Associates
Dictyostelium development and the relationship with temperature
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