Sydney

= **Introduction ** =

My name is Sydney-like-the-city Gibson-like-the-guitar, and I was born and raised in Oklahoma City, OK. I found the Boston Leadership Institute's summer programs after extensively searching for a summer program that could further my education in the animal science and biological field.

I've been interested in biology from a very early age; I knew I had a passion for biology before I even knew the meaning of the word. My mother often tells me of how, when I was a toddler, I cried during snowstorms because I was worried the trees would be too cold. During my elementary school years, I was swept into a passion for paleontology. To this day, I can still tell you more about the prehistoric world than I can tell you about the town I grew up in. Once I got older, I realized my interest in terms of a career path lay more along the lines of something to do with animals that were still alive. Nowadays, frequenting zoos, volunteering at local animal shelters, and taking courses in school keep my interest satisfied.

My academic science experience thus far includes Honors Biology and Pre-AP chemistry at Casady School, as well as a summer medical forum in 2012 with the NYLF organization.

My hobbies include freestyle roller skating, drawing and painting, and long distance running. Additionally, I spend most of my free time at home reading and looking after my younger sister, Sara. My mother recently began working towards a Respiratory Therapy degree at a community college in our area. Since school takes up a large portion of her time, I've been Sara's primary caretaker for the majority of the past two years.



= Research Project: The Story of the American Chestnut Tree =



**The History** In pre-colonial, and even more so during colonial New England, it was difficult to exaggerate the importance of the massive //Castanea dentata//, the American chestnut tree. D ue to a combination of rapid growth and a large annual seed crop, o ne out of every four trees in the virgin Appalachian forest belonged to this deciduous, hardwood species of beech. This prevalence held true from Maine and Southern Ontario to Mississippi, and from the Atlantic coast to the Appalachians. The trees produced reliably abundant nuts each fall, and thus were a significant food and shelter source to the indigenous animals such as black bears, moose, elk, white-tailed deer, mountain lions, wild turkey, Carolina parakeets, and even humans. Essentially, these trees were part of the very backbone of the complex ecological system in their domain.

Often referred to as the "Redwoods of the East," the American chestnut tree historically grew to heights of more than 100 feet tall, and had a diameter of over ten feet. The wood of the American chestnut was easy to split, water-resistant, rot-resistant due to a high tannin content, and grew at a rate fifty percent greater than the leading oak varieties. These qualities made the American chestnut economically vital to early American settlers and a mainstay of loggers, who could fill an entire train car with boards cut from a single tree. The cut timber was then utilized for more diverse purposes than any other type of wood; the timber became housing structures, furniture, instruments, telephone and telegraph poles, fence posts, and more. Tannin extract from the wood made the chestnut trees crucial for tanning heavy leathers, as well. The American chestnut tree was truly a cornerstone tree species. Up to the turn of the 20th century, the tree dominated the forests of the region and was hailed for its versatility. However, one of the American chestnut trees advantageous qualities was simultaneously a downside: the massive size of the trees made accessing their nuts difficult, prompting those wishing to harvest chestnuts as a cash crop to search for shorter, smaller varieties. Introduction of the Japanese Chestnut Tree Asiatic varieties of chestnut trees imported to New England in the 1870's were an apparent solution to many American's chestnut harvesting difficulties. Smaller in statures and wide-spreading branches made the Chinese (Castanea mollissima) and Japanese (Castanea crenata) varieties' nuts more accessible, and many orchard keepers sought to grow them in place of, or in addition to, the native American chestnut trees.
 * Sudden Near-Extinction **

Some of these exotic varieties, particularly the Japanese variant//,// harbored //Cryphonectria parasitica,//a necrotrophic fungal disease now known simply as Chestnut blight. The disease was first discovered and documented in American varieties in 1904 by Hermann Merkel at the New York Zoological Park, which is now the Bronx Zoo. The Asiatic varieties of chestnut that had evolved alongside the fungus had resistance to the blight; it damaged the trees only cosmetically. The same could not be said for the American chestnut. By 1910, the American chestnuts in the Bronx Zoo were dying. Within the following 50 years, the fungus' spores spread through and infected an estimated four billion American chestnuts along the Appalachians. Today, nearly all of the chestnuts sold for culinary purposes come from the Chinese variety, and oak has replaced chestnut wood within the timber industry.

The Blight
// Cryphonectria paracitica // enters the tree trunk through a wound and colonizes beneath the bark, creating a distinctive canker on the bark as a mycelial fan forms beneath. The spreading hyphae produce a large quantity of oxalic acid, lowering the normal pH for 5.5 within the bark to 2.8, which is toxic to plant cells. This results in the death of the cambium, a layer of bark composed of embryotic cells vital to plant growth.

As the blight spreads throughout the American chestnut, the outcome is not the true death of the tree but the suffocation of the stem. The blight manages to kill the vast majority of the tree but it cannot out-compete many of the microbes living within the roots of the American chestnut. Since chestnut trees have the ability to sprout from a stump, the result of the blight is not the extinction of the American chestnut, but instead what has been referred to as a "functional extinction." The infected American chestnuts become stumps that occasionally shoot up, but are overtaken by the blight before they ever grow tall. These "living stumps" now litter areas along the Appalachians in ghost forests, remnants what they once were.

Shortly after the destruction of the American chestnuts in the Bronx Zoo in 1910, leading American plant explorers collected the seeds of the Asian varieties of chestnut that were resistant to the blight. Since chestnut varieties crossbreed with considerable ease, the creation of Chinese-American and Japanese-American hybrids was the natural first approach to inventing a blight-resistant tree. However, the Asian varieties of chestnut aren't nearly as hardy as the American chestnut, and the early hybrids never resulted in a tree as versatile as the pure American variety. In addition, the resistance genes found in the Chinese and Japanese chestnuts are only partially dominant, making the creation of a truly resistant hybrid much more difficult. The most extensive planting of early hybrids were carried out between 1947 and 1955 by the Lesesne State Forest in Virginia. Out of all the hybrids planted, relatively few survived the blight.
 * Genetic Engineering and Attempts at Recovery **

Another early attempt at combating the chestnut blight consisted of the creation of chestnut-free zones several miles long, meant to isolate populations of the uninfected American chestnut and ensure that the blight did not spread from one side of a zone to another. This effort was ultimately futile, as it was discovered, much too late, that chestnut blight can infect and survive in oaks (although it does not kill them). Discouraged and otherwise preoccupied and financially drained by war, most New England states abandoned breeding projects before 1960.

**Backbreeding Resistant Strains** In the 1980's, another attempt to revive the American chestnut was made by the private, non-profit The American Chestnut Foundation (TACF). Using a method derived from Mendelian genetics called backcross breeding, the organization aimed to create a resistant hybrid that was phenotypically identical to a pure American chestnut in every way other than in its resistance to // Cryphonectria paracitica. //Previously, backcross breeding methods had only been attempted in wheat and barley.

Backcross breeding involves crossing a hybrid organism with one of its parents or an individual genetically similar to its parent, so that offspring with a genome closer to one parent can be obtained, while certain traits from the second parent can be selectively maintained or certain traits from the first parent may be methodically excluded. In other words, backcrossing is a process of gene knockout through multiple generations.



In chestnuts, blight resistance genes usually express themselves clearly when present in seedlings purposely inoculated with a virulent form of the blight pathogen. Only seedlings displaying the greatest resistance are used for further backbreeding with an American parent. When lines of backbred chestnuts result in primarily American genomes, they are then intercrossed in order to obtain a fully resistant tree that no longer contains any genetic coding for blight susceptibility. TACF's breeding system incorporates a wide range of American chestnut parents from multiple areas along the Appalachians in order to ensure proper genetic diversity and sustainability in their final product. However, this results in a much longer breeding process and requires breeding multiple generations of partially-resistant trees. Several generations of TACF's trees have been planted throughout the last decade with much success, although as of July 2013 they have not obtained a fully resistant specimen. Their efforts to breed strong, pathogen-resistant American chestnuts are still ongoing today.

Alternative Approach: Transgenic Trees
Although The American Chestnut Foundation's backcrossing efforts appear promising, William Powell of SUNY College of Environmental Science and Forestry in Syracuse, New York, has another way of approaching the American chestnut revival. He and his colleague Charles Maynard have been working on genetic engineering efforts for the American chestnut at SUNY-ESF for more than two decades.

The goal of the team at SUNY-ESF was to build a better American chestnut tree. First, however, they had to figure out a method of tampering with the chestnut genome in the first place. Unlike other plants being genetically modified, chestnut trees cannot be regenerated from a sample of leaf tissue. Instead, an immature nut must be harvested, then its embryo and soaked in a medium that induces replication. This prerequisite method for genetically engineering chestnut trees took sixteen years to develop. Once that was completed, he was able to begin tampering with the American chestnut genome.

The direction of Powell's research came as a result of an article abstract one of his graduate students brought back from a meeting of the American Society of Plant Biologists in 1997. The article, entitled // Expression of Oxalate Oxidase in Transgenic Plants Provides Resistance to Oxalic Acid and Oxalate-Producing Fungi, // provided the crew at SUNY-ESF exactly what they needed. Powell tracked down the author of the article, Randy Allen at Texas Tech, and obtained copies of the gene that Allen had used for testing. All Powell's team needed to do was figure out how to make it work in the genome of the American chestnut.

Oxalate oxidate is an enzyme that occurs in common wheat (Triticum aestivum). It catalyzes the reaction C 2 O 42− + O 2 + 2 H + > 2 CO 2 + H 2 O 2 , which allows for the rapid oxidation of oxalic acid, H 2 C 2 O 4, the toxic chemical produced by // Cryphonectria paracitica. //The gene responsible for encoding oxalate oxidase (OxO) was thus inserted into the genome of an American chestnut cell.
 * The Science Behind It **

In March 2013, the SUNY-ESF team created transgenic American chestnuts transformed with the OxO gene and a  strong constitutive promoter, CaMV 35S. The trees showed legion lengths comparable to the resistant Chinese variety, //Castanea mollissima, // when introduced to the blight. This is the first report on enhanced pathogen resistance in transgenic American chestnut.

**Current Status** On April 18th, 2013, 10 of Powell's transgenic trees were planted at the New York Botanical Garden, directly across the street from where the chestnut blight was first discovered in 1904. The planted trees will be the first true test of whether or not Powell's trees will remain blight-resistant with age. Powell and his team have expressed confidence in their design, and plan to continue trying to develop a better American chestnut.

Powell has expressed intentions to incorporate several resistance genes from Asiatic varieties of chestnut into the transgenic American ones, in addition to the originally incorporated wheat gene. He would also like to begin crossbreeding his resistant trees with the few surviving wild ones in order to build up a diverse population, all containing the protective transgenic material. Before any breeding or restoration programs can be carried out, Powell will need approval from the USDA, the EPA, and the FDA. If the transgenic trees are incorporated into the wild, it will be the first instance of a genetically modified organism intentionally being introduced to open land.

= Design Project: N-Acyl Homoserine Lactone (N-AHL) Directed Bdellovibro bacteriovorus =

The Problem
Stewart’s wilt, also known as corn blight or bacterial blight, is caused by //Pantoea stewartii//. This plant pathogen is a facultative anaerobic, nonflagellate, nonspore-forming, nonmotile rod-shaped Gram-negative bacteria that seriously affects several corn types, such as sweet, dent, flint, flower, and popcorn. It is epidemic in the mid-Atlantic and Ohio River Valley areas and in the southern half of the Corn Belt. Other occurrences of the blight coincide with occurrence of the corn flea beetle, //Chaetocnema pulicaria//. The corn flea beetle is the primary vector of //P. stewartii//, which annually overwinters in the gut of the beetle. Each spring, adult beetles feast on fresh corn seedlings and transmit the blight via fecal contamination of the wounds they create on the plant. Surviving kernels from these infected specimens can also harbor the disease, resulting in a systemic infection of the seedling upon planting. Ultimately, Stewart’s wilt results in affected crops producing fewer and smaller ears of corn.

The greatest economic impacts of Stewart’s wilt on field corn occurred in the 1930’s, during a series of particularly hot summers and mild winters that resulted in thriving populations of flea corn beetles for several growing seasons, and during epidemics in the 1990’s when, Stewart’s wilt became a significant economic issue for the entire corn seed industry due to logistics of trading large volumes of field corn seed throughout the world. Today, economic impact upon field corn is minimal due to well-bred resistant hybrids. Most varieties of sweet corn, however, are still extremely susceptible to the blight and cause annual strain on sweet corn farmers in areas where the disease occurs. Yield losses in susceptible varieties of the corn after early-stage infections frequently range from 40 to 100%. Additional economic impacts of Stewart’s wilt include many phytosanitary regulations imposed upon sweet corn seed traders by trading partners. These regulations affect commerce by preventing seed export or adding additional costs to seed producers from areas known to harbor flea corn beetles.

Current Management Issues
The current prevention and management methods for Stewart’s wilt consist of spraying corn seeds, and then later the corn sprouts, with a cocktail of the insecticides clothianidin, imidacloprid and thiamethoxam. Repeated spraying is recommended in order to establish the presence of the insecticides within the field. The insecticides are not targeted at preventing or destroying //P. stewartii//, but aim to control the population of the corn flea beetle. Corn flea beetles are not an inherent threat to the health or growth of crops. The corn flea beetle injures corn plants by removing the outer surfaces of their leaves. These scratches rarely result in economic impact. The transmission of //P. stewartii// to the corn is the primary motive behind controlling the corn flea beetle population. Thus, the main organism necessitating preventative action is //P. stewartii//, not the corn flea beetle.This has not been shown to decrease incidence or severity of the disease in susceptible varieties of corn. All three of the aforementioned insecticides, however, belong to the class of neuro-active insecticides known as neonicotinoids. Neonicotinoids are chemically related to nicotine, and are the first new class of insecticides introduced in the last 50 years. Imidacloprid, in particular, is the most widely used insecticide in the world.

In March 2013, the American Bird Conservancy called for a ban on neonicotinoids and published a review of 200 studies showing their toxicity to birds, aquatic invertebrates, and other wildlife. Neonicotinoids have also been specifically named as the primary cause of honey-bee colony collapse disorder. In April 2013, the European Union voted to impose a two-year ban on neonicotinoid use in bee-attracting crops in hopes of seeing honey-bee population recovery. Although the Environmental Protection Agency has recognized the harmful and potentially long-term effects neonicotinoids have on honey-bee populations, no measures have been taken to restrict their use within the United States, partially do to the costs and efforts associated with using alternative forms of pest control. So, Stewart's wilt is a problem, the corn flea beetles that transmit //P. stewartii// are not, and the current environmentally-toxic methods of controlling Stewart's wilt target the beetles, not the bacteria. Clearly there is room for improvement of the system. Suppose a technology could be developed in such a way that it targeted //P. stewartii// and prevented corn blight in an environmentally friendly way. It would need to be able to effectively locate //P. stewartii// within the wounds of corn leaves, then destroy it without the use of harsh chemicals that otherwise damaged the plant. In order to imagine such a technology, a greater understanding of how Stewart's wilt operates is required.

How the Pathogen Works
//P. stewartii// attacks the infected plant by colonizing the plant’s vascular system and producing extracellular polysaccharides (EPS) that cause obstruction of xylem vessels, which causes stunted growth, wilting leaves, withering, and death. The initial symptoms of Stewart’s wilt often appear as leaf legions surrounding flea beetle feeding scars. These pale legions then spread as streaks along leaf veins. These streaks eventually turn brown and necrotic, and yellow masses of bacteria can sometimes be seen oozing from the legions. Corn kernels become gray and dwarfed, and open cavities often form within the stalk, making the plant highly susceptible to stalk rot fungi in addition to Stewart’s wilt.

The EPS produced by //P. stewartii// are injected directly into corn cells via a type three protein secretion system (T3SS). Production of these EPS are regulated by quorum-sensing regulatory proteins that prevent the injection of EPS into the corn cells until a certain, effective population density of //P. stewartii// bacteria are present, ~2 X 10^8 cells/ml when grown in liquid culture. Although quorum-sensing systems in Gram-negative bacteria all reply on the same basic principle of interactions between N-acyl homoserine lactones (AHLs) and corresponding receptor proteins, the mechanisms and reactions that occur within each system vary, and to current knowledge each species of bacteria has an AHL with a slightly different shape due to differences in the composition of their R-group side-chain. Chain lengths vary from 4 to 18 carbon atoms and in the substitution of a carbonyl at the third carbon.

The quorum-sensing system in //P. stewartii// is primarily composed of the EsaI and EsaR proteins. EsaI is an N-acyl homoserine lactone (AHL) signal synthase, and EsaR is the cognate AHL-responsive transcription factor. The AHL produced by //P. stewartii// is N-(3-oxo-hexanoyl)-L-homoserine lactone (OHHL). When concentrations of OHHL in the extracellular matrix of //P. stewartii// are low, EsaR dimerizes and binds the DNA, thereby repressing target genes involved in synthesis of EPS. When concentrations of OHHL are great enough to be detected by the EsaR receptor proteins, EsaR binds in a 1:1 ratio with OHHL and detaches from the DNA sequence, allowing for the transcription of the rcsA gene, which codes proteins needed for EPS construction. In other words, the EsaR protein is a repressor, with derepression dependent upon OHHL. This fact will be important to the mechanics of the completed design.

The Solution: Another Bacteria
//Bdellovibrio bacteriovorus// is a predatory, obligate aerobic, Gram-negative bacteria discovered by Stolp and Petzhold in 1962. This comma-shaped bacteria is approximately 0.2 to 0.5μm wide and 0.5 to 2.5μm long and highly motile; specimens have been recorded swimming over 100 times their body length per second with the use of a single sheathed polar flagellum. //B. bacteriovorus// has been located in a wide range of terrestrial and aquatic environments such as soil, sewage, and river water.

The most distinct aspect of //B. bacteriovorus// is its biphasic predatory life-cycle. //B. bacteriovorus// preys solely on other Gram-negative bacteria in a parasitic manner. In the “attack phase,” //B. bacteriovorus// attaches to, and then lyses, the outer membrane of its prey. It then enters the cell, seals the membrane hole and forms a two-cell complex called a bdelloplast. //B. bacteriovorus// then breaks down the prey cell’s molecules, which it uses to elongate and form a filament. After exhausting available nutrients, the filament divides into several progeny //Bdellovibrios//. These progeny become mobile shortly before lysing the host cell and entering the open environment. They are then considered to be in the free living and motile phase, during which the traverse their environment in search of prey. The life cycle takes an average of one to three hours, and progeny cell number is dependent upon the size of prey in which they form.



Due to the necessity of prey for the reproduction of most strains of //B. bacteriovorus//, efficient motility is important to //B. bacteriovorus//. In B//dellovibrio bacteriovorus// strain HD100, the wild-type strain on which this article will base its information, genome sequencing and analysis have shown that there are three sets of motAB operons. These operons, Bd0144-Bd0145 (MotA1-MotB1), Bd3021-Bd3020 (MotA2-MotB2), and Bd3254-Bd3253 (MotA3-MotB3), code proteins involved in flagellar rotation.

MotAB protein pairs are transmembrane protein complexes which affect flagellar rotation by undergoing conformational changes in response to ion gradients maintained by the electron transport system of the cytoplasmic membrane. These changes act upon the rotor protein FliG, which causes rotation of the MS ring, rod, hook, and filament, thus causing the bacteria to swim.

Individual deletion of the motA gene sequences in a laboratory setting has revealed that each operon contributed to flagellar-mediated motility and that no single pair of proteins was essential for neither movement nor exit from the bdelloplast. The singular flagellum of B. bacteriovorus is thus thought to be powered by a hybrid motor controlled by all three pairs of stator proteins. However, deletion of MotA3 significantly reduced swimming speed by nearly a third compared to the minute speed differences observed in specimens with the deletion of MotA1 or MotA2. The MotAB3 operon therefore plays the most significant role in the functional ability of the bacterium’s flagella. Causality of the increased significance of the MotAB3 operon is believed to be related to aspartate resides in the MotB3 stator protein that are not found in MotB1 or MotB2.



These MotAB protein complexes, however, only control the swimming power of //B. bacteriovorus//; they do not regulate swimming direction of the bacterium. //B. bacteriovorus// utilizes the “run and tumble” method of movement in which it alternates between phases of “running” or “smooth swimming” in a straight line and “tumbling” in a stationary rotation. This creates a pattern of movement known as a “random walk.” The change in movement occurs due to a change in flagellar rotation. A counter-clockwise rotation of the flagella of //B. bacteriovorus// causes a straight, smooth swim. A clockwise rotation induces tumbling. Many bacteria, including // B. bacteriovorus //, have adapted a way of having a “biased random walk” that favors movement across a concentration gradient towards or away from particular chemicals so as to benefit or protect the bacteria. This phenomenon is known as chemotaxis.

The chemotactic system utilizes methyl-accepting chemotactic proteins (MCPs) which are transmembrane sensor proteins that detect molecules within the extracellular matrix. They react either directly with a ligand or with ligand-binding proteins, then transduce the signal down their hairpin structure to signaling proteins within the cytoplasm. These proteins, known as the Che complex, control the frequency the bacteria goes into the rotational “toggle” mode. Increasing concentrations of an attractant increase the likelihood that the bacteria will orient itself in a direction of positive chemotaxis, or towards the greatest level of concentration.



The Synthetic Element
Now, hypothetically, if both the expression of the MotAB3 operon and the chemotactic system of //B. bacteriovoru//s could be adapted to express and respond only to the particular N-Acyl homoserine lactone emitted by the EsaI proteins in //P. stewartii//, the statistical probability of //B. bacteriovorus// selecting //P. stewartii// for prey may increase to such an extent that the mutated B. bacteriovorus could be considered a unique biopesticide for that pathogen. The engineered bacteria would simply need to be mixed into the crop soil in great abundance and/or sprayed upon the plants themselves after being suspended in an aqueous solution. Two major alterations of the //B. bacteriovorus// genome would be necessary for such a specimen. First, the addition of the esaR gene such that the EsaR protein acts as a repressor of the MotAB3 operon, thereby making significant swimming speed dependent upon detection of OHHL molecules from P. stewartii. As previously discussed, the EsaR protein in //P. stewartii// acts as a repressor. Therefore when this protein is placed on the promoter of the MotAB operon, expression of the proteins MotA3 and MotB3 will not occur until the corresponding ligand for EsaR is detected.

Second, replacement of the natural methyl-accepting chemotaxis proteins with artificial MCPs that recognize N-(3-oxo-hexanoyl)-L-homoserine lactone (OHHL) as their ligand. Evolutionary adaptations have led to a wide range of MCPs that accept an equally diverse range of molecules as ligands. Thus, the creation of an OHHL-accepting MCP with relative ease is not unrealistic. Once the OHHL binds with this artificial MCP, it will set off the usual chain reaction of proteins within the chemotactic system that induce a biased walk towards the greatest concentration of OHHLs, hence causing //B. bacteriovorus// to swim towards //P. stewartii.//

Because these two alterations of //B. bacteriovorus// are regulated by the same external chemical, the two responses will occur simultaneously when the OHHLs of //P. stewartii// are present. Ideally, this concurrent swim speed increase and directional bias will “lock in” //B. bacteriovorus// to the desired prey. A simple truth table can be constructed: ||= 26.5 +/- 1.8  ||
 * = Detection of OHHL by B. bacteriovorus ||= Positive Chemotaxis ||= Transcription of MotAB3 ||= Mean Swim Speed (μm/s) +/- SD* ||
 * = 0 ||= 0 ||= 0
 * = 1 ||= 1 ||= 1 ||= 63.2 +/- 5.5 ||
 * source: []

Upon concentration of // P. stewartii // to the extent at which pathogenicity occurs (when EPS is produced), // B. bacteriovorus // will speed up, swarm the area and prey on the pathogen. Predation should continue beyond the point of merely lowering the concentration of // P. stewarti // i, because once the original attraction to the region occurs and draws // B. bacteriovorus // to the infected site on the leaf, // B. bacteriovorus // will still continue to prey upon // P. stewartii // specimens it comes into contact with, despite a lowered speed and loss of chemotaxis once the concentration of P. stewartii is lowered below the point of being detected by MCPs. // P. stewartii // are naturally nonmotile, therefore a slowed movement of // B. bacteriovorus // that is already in close proximity should not hinder predation and near-sterilization of the leaf wound.

Considerations
Potential problems with the design of the system arise when one considers that a preference and direction towards a specific prey does not translate to one-hundred percent certainty that the prey selected by //B. bacteriovorus// will be //P. stewartii//. Fortunately, testing of the engineered bacteria could be conducted with relative ease. Engineered //B. bacteriovorus// should be placed in an environment abundant in Gram-negative bacteria, including //P. stewartii//; predation levels on //P. stewartii// by the engineered //B. bacteriovorus// should then be compared to a control sample with an identical set-up in which the engineered bacteria were replaced with wild-type //B. bacteriovorus// HD100. Since neither //B. bacteriovorus// nor //P. stewartii// are human pathogens, only minimal safety precautions would be necessary for these trials.

Assuming optimal predatory behavior from the engineered //B. bacteriovorus//, this design, could eradicate the need for the use of heavy pesticides throughout the United States’ corn fields. Engineered //B. bacteriovorus// mixed into crop soil and/or sprayed on corn seedlings upon corn flea beetle sighting could potentially control the concentration of //P. stewartii// to such an extent that vascular colonization and thus crop devastation never occurs.

Since replication and multiplication of //B. bacteriovorus// occur each time a specimen successfully preys upon another bacterium, the populations of //B. bacteriovorus// should theoretically be sufficiently self-maintainable within a crop field and therefore not require reapplication within one growing season. However, since motility of the engineered bacterium will be compromised in the absence of //P. stewartii//, significant population survival beyond the point of management of Stewart’s wilt is unlikely.

Perhaps more importantly than management of Stewart’s wilt, this model for the adaptation of //B. bacteriovorus// could potentially be adapted to operate in response to any Gram-negative bacteria that uses an AHL-based quorum-sensing system, and may provide an alternative option for controlling antibiotic resistant strains of bacteria such as //Pseudomonas aeruginosa// or //Staphylococcus aureus.//

= = = Sources = **American Chestnut Trees** [] [] [] [] [] [] [] [] [] [] [] [] [] [] [][]

Stewart’s Wilt (general)
[] [] [][]

Quorum Sensing:
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Bdellovibrio bacteriovorus, motility and chemotaxis:
[|http://microbewiki.kenyon.edu/index.php/Bdellovibrio_bacteriovorus#Cell_structure_and_metabolism] [] [] [] [] [] [] [] [] [] [] [] [] []