Abstract This report explains in detail the function, structure and assembly of flagella in E.coli and Salmonella, using plain language and a number of diagrams. Movement (chemotaxis) is the primary function of flagella but its design also incorporates efficient repair capability and antigenic variation. In Salmonella and E.coli the flagellar filament is a homopolymer of flagellin monomers, although other species (such as Helicobacter) build their flagella from mixtures of two types of subunit. All the properties of the functioning filament are reflected in the structure of the flagellin monomer, which has conserved and variable regions, regions targeted by chaperones and coiling enzymes and regions evolved specifically for interaction between monomers. Chemotaxis is driven by a proton motive force (as in oxidative phosphorylation) and the basal complex that converts this energy into rapid rotation of the flagellum is highly complex.
From the Paper "Many bacteria are motile and exhibit chemotaxis ? migration through the extracellular medium towards attractants (e.g. carbon sources), and away from repellents (e.g. antibiotics). The majority move using flagella ?protein structures variable in number and position (Box 1) that generate thrust by rotating like propellers. Flagella are 15nm in diameter and can be observed under light microscopy after thick metal staining or using advanced microscopy techniques such as electron microscopy. Because of the competitive advantages of chemotaxis, there has been strong selection for efficient chemotactic apparatus and flagellar efficiency. The flagellum is based in the bacterial surface layers where a complex array of proteins forms the flagellar motor. Resembling the electric rotary motor and the membrane-bound F1F0-ATPase, and powered by a proton influx across the inner membrane, this highly efficient machine is merely 30nm in diameter. Its mechanism is the subject of ongoing research."
Abstract This paper explains that the e-coli bacillus is a microbe about which much is known but has defied efforts to stamp out its unpleasant impact upon human health. The author points out that these extraordinarily tiny cells are invisible to the naked human eye and can accumulate in vast quantities in food preparation areas without individuals being aware of them. The paper relates that e-coli cells are prokaryotic and distinguished by a single, circular chromosome; such cells also contain DNA as plasmids. The author states that, in simple cases of e-coli poisoning, rehydration is essential; however, there is no evidence that antibiotics improve the course of the disease and/or expedite recovery and anti-diarrheal agents are strongly discouraged. The paper concludes that this tiny "bug" certainly seems resilient enough to cause human beings misery for some time to come.
From the Paper "The living environment and the reproductive process of the e-coli cell are also interesting. Simply put, e-coli most commonly flourish in the intestines of warm-blooded animals. In terms of reproduction, the process is simply one of binary fission, with the circular DNA chromosome replicated. The cell splits into two identical cells with each cell having the same DNA; it should be pointed out that, during the fission process, the identical chromosomal material attaches itself to different parts of the cell membrane so that "replicate" material is firmly anchored where it needs to be when the cell begins to pull apart and halve."
Abstract This a detailed, and well researched paper discussing how e. coli can be prepared and used for study of Molecular genetics. The author looks at how e.coli lends is an ideal candidate for this area because it is such a simple organism. The paper also examines how scientists have been immeasurably helped in their progression of learning about the fundamentals of molecular genetics by the fact that E. coli can be induced into competence through a number of methods. The paper includes numerous illustrations.
From the Paper "Most of us, when we think of Escherichia coli at all, tend not to have very pleasant associations with the organism. It is in fact among the organisms that are most likely to affect (and infect) households. While E. coli is actually an integral part of the normal gastrointestinal flora, certain strains can cause diarrhea, fever and vomiting by one of three ways: by giving off toxins, by directly invading the mucosal lining of the intestinal wall, or by adhering to the intestinal wall. A person infected with E. coli may also have malaise or overall weakness and abdominal cramps. And a new virulent strain of E. coli, which is passed to humans via contaminated and improperly stored or prepared food, can cause a fatal kidney condition ? a finding that has prompted public health and food industry officials to suggest changes in the meat-inspection process, including the irradiation of some ground beef. But the bad name that E. coli deserves as a very nasty bug that infects humans must be offset by the fact that study of this organism has vastly increased our understanding of the field of molecular genetics. This paper outlines some of the most important basic principles of this field by focusing on the specific findings that studying E. coli have allowed scientists to derive."
Tags: bacteria, genetics molecule molecular geneticsgenes dna rna cell, recombinant
Abstract The writer points out that the purpose of this laboratory was to acquire fundamental knowledge and experience in microbiological procedures, specifically in growing bacterial colonies on a nutrient medium under controlled conditions. In this case, Escherichia coli (E. coli) bacteria were grown on nutrient agar, contamination was minimized by keeping the surroundings sterile, and all agar plates were incubated. The writer notes that the first part involved making five serial dilutions from a bacterial suspension in order to pinpoint colony numbers. The second experiment compared two methods of spreading bacteria across agar plates using streaks. The goal was to isolate single colonies. Lastly, the third portion of the laboratory involved replicating plates from a master plate in order to isolate strains of mutant bacteria onto different nutrient mediums and determine bacterial auxotrophy to these nutrients.
Outline:
Introduction
Materials and Methods
Results
Discussion
References
From the Paper "In the streaking experiment, method B proved to be much more effective for isolating single colonies. The different streaking methods may have contributed to the morphological differences between the E. coli on the two plates. There were evident differences in the size and colour. Since method B was dominated by spaced out single colonies, the darker colour and larger size can be attributed to more nutrients being available to each colony, and more room (surface area) for growth. For the same reason, the more crowded groups of bacteria on the method A plate were a lighter colour and generally smaller. Aside from these two differences, the E. coli shared great resemblance, and based on morphology alone, should not be classified as different species. Nonetheless, the only way to determine whether or not two sets of visibly different bacteria are genetically different is to actually observe their DNA."
Abstract This paper reports on an experiment in which, using sewage water to locate the E.coli bacteriophage, the bacteriophage was isolated from the original culture and placed in an enriched medium to grow and reproduce. The author continues that each one of the plaques represents a viron from the original culture, and, by counting the plaques, they were able to determine the concentration of bacteriophages in the culture. The author reports that findings among the different lab groups differed significantly, but this could be explained by the fact that the experiments were performed on separate days a week apart.
Table of Contents
Abstract
Introduction
Materials and Methods
Results
Discussion
From the Paper "E.coli was grown for 48 hrs in TSB tubes at 37degrees C by the lab assistant. (Sewage from the Cheney Sewage Works.) The sewage was then centrifuged and the bacteria containing portion was filtered using a 100 mL filter apparatus. I picked up my E.coli and filtered sewage from the lab assistant. Next, I gathered 7 plates of triptocase soy agar. These were labeled 1x10^-3 to 1x10^-9 and placed into the incubator to bring their temperature up to that of the bacteria/phage solution to be added later. 9 Eppendorf tubes were labeled 1x10^-1 to 1x10^-9, these were then set aside. Sterile saline was then gathered and using a Beckman autopipetter. I transferred 900 uL of sterile saline into each Eppendorf tube."
Abstract This paper examines the E.Coli outbreak that took place in 1996 when 70 children were found infected with the bacteria after drinking Odwalla's apple juice. The Court heavily penalized the company as it was revealed during FDA investigation that Odwalla was not following proper quality control measures and its products were not being tested for bacterial contamination. Douglas Levin had to take drastic measures to win back the trust of Odwalla's customers.
Abstract The paper relates the outbreak of E. coli that was found to have been caused by unpasteurized apple juice sold under the brand name of Odwalla. The paper discusses how the company did not shirk its responsibility and this ensured that the public perception of the company was a positive one. The paper highlights the CEO's notable response and illustrates how the first reaction by the company involved is of critical importance. The paper points out, however, that if the company would have exercised the same care beforehand, the company's losses and lessons from this experience would have been avoided and unnecessary.
From the Paper "When this type of event takes place, the first response by the company involved is of critical importance. When Odwalla's CEO Stephen Williamson responded he did so with sincerity and sympathy that was quite notable."
"Not only was the recall handled in a professional and timely manner, but Williamson also initiated other reforms that were just as timely and they proved quite effective in the long run as well."
Abstract This paper discusses the threats of infectious organisms, with a focus on their ports of entry. The paper explains that typical portals of entry include the mouth, ears, eyes, urethra, nose, and skin, while non-typical portals might include wounds, broken skin, insect bites, or even animal bites or stings. The paper explores the E. coli bacteria, Hepatitis A ,and Guardia Lamblia, providing explanations of how these diseases may be contracted and various methods for treatment and prevention.
Outline
Introduction
The Mouth and Gastrointestinal Tract
Defense Mechanisms
The E. coli Bacteria
E. Coli Taxonomy and Virulence
Treatment and Prevention
Hepatitis A
Taxonomy
Treatment and Prevention
Guardia Lamblia
Taxonomy
Treatment and Prevention
Conclusions
From the Paper "Indeed, the specialized preferences of many organisms with regard to ports of entry are so consistent that it is often taken as a hallmark of a particular organism in the diagnosis phase. This is especially important when one notes that the symptoms of characteristic of a specific infection usually give clear clues as to the point of entry. Although it is important to consider the point of entry when diagnosing the cause of illness in a patient, it can also be important for many aspects of disease prevention, especially when a high risk for a particular organism is present in one's environment. For example, if one knows that he or she is working in an environment where there is a high incidence of an airborne pathogen, steps can be taken (the wearing of masks the use of patient isolation procedures for example) to minimize possible exposures to that pathogen."
From the Paper "Escherichia coli is a gram positive, facultative anaerobe that occupies a symbiotic relationship with the large intestine of several animals including that of humans. This mutually beneficial arrangement provides adequate nutrition and safe haven for the encapsulated bacteria while providing the host with vitamin K and B-complexes (Tierney et al., 1998). E. coli is rapidly introduced into the sterile newborn through food, water and as a direct result of the birthing process. The host's colon is rapidly colonized by these and other bacteria that compete among themselves for position and acquisition of resources.
E. coli is the most common cause of urinary tract infections and ..."
This paper discusses crisis management by Odwalla, Inc., a natural, unpasteurized fruit juice company, after a fatal outbreak of E. coli O157:H7 in their apple juice.
Abstract This paper explains that although most small companies would never have survived an E. coli crisis, Odwalla weathered the storm and is now the subject of a best practice studies on crisis management. The author points out that Odwalla was not innocent and committed major management errors: Significant flaws in its safety procedures, poorly maintained citrus-processing equipment, an insular culture without a clear system of corporate checks and balances, no internal oversight procedure and a board of directors comprised of business friends of its founder. The paper reports that some of the crisis management included the company accepted full responsibility for the crisis, in all interviews with the media, expressed sympathy and regret for all those affected and promised that the company would pay all medical costs.
From the Paper "Most importantly, Odwalla took steps to stop the problem that had caused the E. coli contamination in the first place. The company admitted that its neglect of pasteurization had been wrong and moved quickly to introduce a process called "flash pasteurization" which could guarantee that E. coli had destroyed while maintaining better flavor that pasteurization. Odwalla also invested $1.5 million in new safety procedures within a year of the recall. Today, the company adheres to a Hazard Analysis and Critical Control Points program that exceeds FDA requirements, tests every batch of juice for purity, performs daily microbiological tests, and leads the charge for higher government standards across the juice industry. While Odwalla's public relations campaign was a success, it's important to remember that the company was guilty of criminal charges of selling tainted apple justice and was fined $1.5 million, the largest ever assessed by the FDA. Odwalla accepted responsibility for the poisonings by portraying itself as unaware of the health dangers of unpasteurized juice, but this doesn?t appear to be the case. Nonetheless, the public responded favorably to Odwalla's highly lauded crisis management tactics."
Abstract This paper examines the outbreak of e-coli in Walkerton, Ontario in 2000. It looks at its causes and effects. It also evaluates the recommendations of the Walkerton Inquiry.
Abstract This paper examines the public health disaster in Walkerton, Ontario when 7 people died from E. Coli in the water supply in the early summer of 2000. It assesses the government decisions that made the Ministry of the Environment's regulatory regime vulnerable to failure. It also identifies the government's neo-conservative philosophy as the key factor in the breakdown.
Abstract This paper provides an overview of peptides and their role in biological processes, how amidation of peptides works and its importance, and a description of the two functional domains of the PAM enzyme (PHM and PAL) and the roles they play in amidation. An assessment of whether amidation prevents C-terminal degradation is followed by a discussion of which peptides/proteins are susceptible to C-terminal degradation by carboxypeptidase. An analysis of whether E. coli can be modified to perform amidation is followed by a summary of the research in the conclusion.
From the Paper "Further, there are currently methods to determine peptide binding to some HLA class II-DR and -DQ molecules; some of these methods measure the relative strength of the peptide -HLA interaction using isolated class II molecules and purified peptides. Other methods are used to predict peptide binding to HLA using computer algorithms (Harding, Mucha, Power & Stickler, 2003). The number of amino-acid molecules present in a peptide is indicated by a prefix: a dipeptide contains two amino acids; an octapeptide, eight; an oligopeptide, a few; a polypeptide, many (Conley, Schwartz & Desforges, 2004). The distinction between a polypeptide and a protein is imprecise and is regarded as being largely academic; some authorities have adopted, as an upper limit on the molecular weight of a polypeptide, 10,000 (that of a peptide that is composed of about 100 amino acids) (Conley, Schwartz & Desforges, 2004)."
Abstract The paper contends that the organization Safe Tables Our Priority (S.T.O.P.) should receive support from the government because the organization could diminish the number of E. coli cases in the United States. The paper describes how S.T.O.P. is committed to ending the contamination of food that leads to illness and/or death. The paper offers an example of a young boy who suffered a horrific death and calls for S.T.O.P. to receive a grant to prevent such unnecessary illnesses and deaths.
From the Paper "The mission of the organization is to put an end to unnecessary illnesses (and deaths in Alex's case) that are caused from food borne pathogens. STOP is committed to ending the contamination of food that leads to illness and/or death when it could be prevented. The organization does not work on other food safety issues like pesticides; however, in the case of Alex, his death was the cause of eating a tainted hamburger. No child should die because he or she has eaten any food contaminated with a food borne illness, and no parent should have to worry that the food they are giving their children is tainted."
Abstract This paper explains that virtually all bacteria strains have viruses specific to them. The paper then describes an experiment that takes coliphages from sewage and, after enrichment and filtration processes, exposes the E.Coli R10 strain to the phages to obtain the phage specific to the strain. The paper further explains that the bacteria strains are grown on agar plates in the presence of coliphages, and strains W3104-A on plates K12 and W3104 and R12-B on plate K12 developed resistance. The paper then reports that the W3104-A strain is further tested and retains its resistance.
Table of Contents:
Abstract
Introduction
Materials and Method
Isolation and Enrichment of Coliphage from Raw Sewage
Filtration of Coliphage Mixtures
Dilution and Plaque Preparation of R10A and R10B E. Coli Strains
Mutation and Isolation of Phage-Resistant E. Coli Strains
Sensitivity of Phage-Resistant Mutants to Bacteriophages
Results
Discussion
Table: Colonies of Bacterial Strains Response to Coliphages
From the Paper "Bacteria have the ability to develop resistance to viruses [6], so as it can be expected some strains (namely W3104-A and R12-B) developed phage-resistant colonies. It is known that certain genetic elements called "episomes" are instrumental in creating phage-resistance in E. Coli strains such as K12 [8]. As indicated in table 1, there were numerous contaminations; this was certainly due to many of the unfiltered cultures that were used. This was done because of time constraints and shortage or missing supplies in the lab."
