Shannon

Hi I'm Shannon, I am 14 years old and from Wellesley, Massachusetts. I will be a sophomore at Wellesley High School this upcoming year. There are four kids in my family. Erin--who is also going to this camp--is the oldest, then there is me, my brother, Connor, and my sister, Bridget. I have a very limited background in biology having only studied it in 7th grade. During that year, we covered the basics of each of the systems, but we didn't go into DNA. Though, I am interested in math and science, which is why I took this course. In the future, I would like to do something that involves those subjects. So, I wanted to see if synthetic biology is an interest of mine. In addition, I would also like to see if I would want to go into AP biology, because it is offered junior year. In my free time, I like to read and play the oboe. At school, I am in the band, which includes the pep band. I am also in the astronomy club, and key club.

Research project: synthetic chloroplast

Chloroplasts that are now found in almost all plants originated from the endosymbiotic relationship between photosynthetic prokaryote and a eukarotic cells. Half a billion years ago, eukarotic cells that had already obtained mitochondria engulfed prokaryote cells. Those that survived were able to provide energy for the eukarotic cells until eventually the eukarotic cells couldn’t survive without the prokaryote. The prokaryote cells evolved to become the chloroplast organelle. This idea became known as the endosymbiosis theory and is now generally accepted.

As the leader of her team, Dr. Palma A. Silver experimented and manipulated endosymbiotic relationships with the intention of creating an endosymbiosisbetween the bacteria //Synechococcus elongatus// and zebrafish embryos. In addition, //E. coli// was tested on to figure out if they could be part of a symbiotic relationship. For the experiment, Silver used the strain //Synechococcus elongatus pcc 7942//. This bacterium is in the Cyanophyta phylum, which is a type of bacteria that get their energy through photosynthesis. The bacteria are also autofluorescent, which helped the experiment, because the bacteria could be concluded to be alive based on whether they emit light. Zebrafish embryos are eukaryotes in their earliest stage of development. The reason for the choice of this specific animal cell was because in their early development stages, the embryos are clear, which allows light to pass through and the Synechococcus to photosynthesize. In addition, they are easy to microinject and are well studied. As the first method for insertion, the zebrafish were injected with live // S. elongatus // and // E. coli //. The embryos were put into egg water and incubated at 30°C. To track the progress of individual embryos, they were put into twelve separate wells. A fluorescence-dissecting microscope checked the development of the embryos, and the bacteria were illuminated with fluorescent lamps from both sides of the tissue culture plate. The result from this was that the zebrafish embryos with // S. elongatus // were able to hatch and thrive, completing the first step to endosymbiosis. During the animal cells development, red fluorescent bacteria were found throughout embryos without the appearance of affecting growth. Additionally, the // Synechococcus elongatus // were also able to survive for twelve days before the experiment were terminated due to the fact that the fish began to develop a pigment that would obstruct light. In contrast, the // E. coli // killed the cells within two hours of injection, and this occurred even when the E. coli were killed by UV prior to being injected.

The second way the //Synechococcus elongatus// could get into the animal cells was if they were engineered with invasin from //Yersinia pestis// and listeriolysin O from //L monocytogenes,// which allowed for them to invade the cells//.// Invasin is a protein that causes the uptake of bacterial cells, and listeriolysin O is a hemolysin that allows bacteria to enter the cytoplasm after the uptake. The bacteria were able to invade the animal cells, and after the 24 hours of infection, the cells were sorted based on their fluorescence. The cells positive for the fluorescence were reattached to a glass-bottomed tissue culture and examined based on their fluorescence. This experiment is one was for endosymbiosis to happen naturally in the environment. The result was that //S. elongatus// with invasin and listeriolysin were able to invade the cells with 4.8% of the cells positive for red fluorescent light.

Another way that bacteria can also enter cells is through phagocytosis, which is where a cell takes in a large object that it will eventually digest. But for the bacteria to survive, they need to avoid digestion. Similar to the first experiment, the E. coli quickly killed the macrophage, and those expressing listeriolysin were able to kill the macrophage even faster then the wild type. Though, the // S. elongatus // were able to remain inside the macrophage for up to two days, but after that they also killed the macrophage. From these experiments, it is expected that //S. elongatus// engineered with listeriolysin O will eventually be able to divide in the cytoplasm. In the current conditions, //S. elongatus// are able to coexist within animal cells, without damaging either of them, and they divide once every eight to twelve hours. If the bacteria are in the light, their autofluorescence slowly decrease in intensity over several days. But, the //S. elongatus// with invasin and listeriolysin were able to escape lysosome digestion and increased in auto fluorescence in the first few days, decreasing only after three days.

Previous research done on endosymbiosis was by Kwang W. Jeon who was able to create an endosymbiotic relationship between an amoeba and a parasitic bacterium. In the time span of several years, the amoebae became reliant on the bacteria, and soon could not survive without it. This is because the amoebae stopped producing an enzyme that was required for survival. But the amebae could stay alive by getting that enzyme from the bacteria, though if the bacteria were removed, the amoebae’s nucleoli would be damaged, since it no longer had access to the enzyme.

Jeon’s experiment proves that endosymbiosis can be sped up and occur in a lab. This means zebrafish could eventually become dependent on the energy produced by the //Synechococcus elongatus//. As a photosynthetic prokaryote, the //Synechococcus// could evolve to perform a similar function as the chloroplast, providing the cell with energy from the sun. This means that a synthetic chloroplast was produced, because it would have been made completely artificially in a lab.

Works Cited: [] [] [] [] [] [] [|http://link.springer.com/content/pdf/10.1007/978-1-4684-5251-8_28.pdf#page-1] [] []