Escherichia Coli together with other strains of bacterium makes up about 0.1 % of the gut (Yoon and Hovde, 2008, 219). Though most strains are harmless, some can be lethal. The bacteria was discovered by Theodore Eschrich in 1884 (Alm, Walk, and Gordon, 2011, p. 107). Their primary mode of disease transmission is fecal to oral. The bacterium also has immense survival skills outside the gut, as it can survive for days. A human being releases more than a hundred billion E. coli bacteria in their ordure every day (Todar, Ubukata, and Hamada, 2005, p. 224). The strain of E. coli notoriously responsible for causing diseases are found in grazer animals especially cows.
Physiological Characteristics
An E. coli cell measures about (1.5*0.75) µm in size. The bacteria do not have a nucleus (prokaryotic) (Alm, Walk, and Gordon, 2011, p. 108). They are rod-shaped and facultative anaerobes; use oxygen for respiration, but can switch to anaerobic respiration in the absence of oxygen. They can ferment lactose; breaking down lactose sugar to acid which is the principle process involved in the making of foods such as yogurt (Todar, Ubukata, and Hamada, 2005, p. 226). E. coli has two primary forms, the rough and smooth forms denoted by (R) and (S) respectively and are non-endospore forming micro-organisms (Alm, Walk, and Gordon, 2011, p. 110). Some strains of E. coli contain an extrachromosomal DNA strand that is responsible for the production colicin which is a harmful component of other types of E. coli (Morales, Attai, Troy, and Bermudes, 2015, p.8).
E. coli multiplication happens vegetatively by binary fusion, and the presence of the sex factor has contributed to modifications in the structure via lateral DNA transfer between the organisms (Morales, Attai, Troy, and Bermudes, 2015, p.11). Transduction is also another method of gene transfer. Genetic material transferred during procreation gives rise to a better offspring of the bacteria.
Understanding the conditions that alter the pathogens virulence potential goes a long way in understanding the pathogenesis of how E. coli causes diseases (Datsenko and Wanner, 2000, 6648). In blood-brain barrier sites, the bacteria enters the central nervous system and causes meningitis. Brain microvascular endothelial cells (BMEC) is essential for blood-brain barrier penetration (Ahmed, et al. 2006. 517). Virulence genes of bacteria are affected by factors such as oxygen tension regulation. Bacteria in chloride and sucrose surroundings portrayed less invasion of brain microvascular endothelial cells. In contrast, more invasion was realized in regions with a higher concentration of iron, magnesium, and potassium.
A “strain” of E. coli is a specific group of the bacteria that exhibit the same characteristics (Morales, Attai, Troy " Bermudes, 2015, p.13). Several strains have developed over the years due to gene mutations during conjugation and hybrid genetic inheritance. The mutation has led to the development of an antibiotic-resistant bacteria that produce certain toxins thus making the infections they cause extraneous to treat. E. coli O157: H7 is said to have a thousand more genes than other E. coli bacteria (Todar, Ubukata, and Hamada, 2005, p. 224). Though E. coli may only cause diarrhea, it may prove lethal for those with low immunity like children and long-term illnesses and may cause death. E. coli bacteria are specific to particular hosts thus it is possible to distinguish infections caused by human ordure or animal ordure.
Mutations have increased the pathogenicity of E. coli, and the bacteria can cause harm to its host. An example is the Shiga E. coli popularly known as (STEC) which can come from raw, undercooked or contaminated foods. The incubation period is usually 3 to 4 days, and the symptoms may last up to 10 days. In rare cases, the signs proceed to the hemolytic-uremic syndrome and can be life-threatening. Doctors recommend washing foods eaten raw thoroughly with soap and clean water before eating them. Since the bacteria cannot withstand temperatures above 40 degrees, cooking foods properly especially dairy products and boiling milk is an excellent step towards eradicating infections.
Unique Features
Escherichia coli exhibits a simple gene structure and a small genome size. It has only about four thousand genes. The human genome contains about thirty thousand genes. They are haploid thus making them fit for experiments since they cannot transfer the effects of the mutations to subsequent generations of the bacteria. E. coli has a tremendous growth rate of twenty minutes per generation making it useful in mass production fermentation processes (Todar, Ubukata, and Hamada, 2005, p. 228). Scientists can study and make conclusions is hours unlike using other organisms with slower growth rates that would take days or weeks.
Understanding the E. coli genome is quite simple, scientists prefer to use it since they can deduce meaningful information. Transforming E. coli with other DNA is successful in techniques of gene cloning because the bacteria can host different DNA. E. coli is easy to maintain; it exists at body temperature, resides in the gut meaning it consumes almost anything and it respires facultatively (Morales, Attai, Troy " Bermudes, 2015, p.15).
Metabolic Characteristics and Environmental Conditions Required for Growth.
One of the cultural characteristics of E. coli is that they are facultative anaerobes. They cannot survive at temperatures colder than 10 degrees Celsius or hotter than 40 degrees. Testing E. coli on nutrient agar, they undergo emulsification in saline conditions, and they appear large, greyish in color, circular shaped, opaque and convex. Due to the many forms, there are variations in the smoothness and roughness (Perna, N.T., Plunkett III, G., Burland, 2001, p. 529).
E. coli on blood agar has beta colonies that are hemolytic, appears big, circular, grey and with high moisture content. Having E. coli on MacConkey agar, the bacteria are circular, smooth moist and occupy the entire margin (Alm, Walk, and Gordon, 2011, p. 109). The lactose fermenting colonies appear flat and pink. E. coli on Mueller Hinton agar are pale straw colored. E. coli on (EMB) and m-ENDO agar, the colonies, look green metallic sheen, but for m-ENDO, metabolic lactose yields an aldehyde and an acid. For E. coli on (VRBA) violet-red bile agar, the colonies have a pink-red color, and under a UV light, the settlements have a bluish fluorescence around them. E. coli on (CLED) cysteine lactose electrolyte-deficient agar, the lactose colonies exhibit a yellow appearance. E. coli on liquid media within 12 hours display turbid homogenous growth. The (R) colonies form agglutinate which is deposited at the bottom of the test-tube. After 72 hours, the surface of the liquid has pellicles built which disseminate when shaken.
Experiments conducted to reveal the optimal temperatures for E. coli showing that they survive more at 37 degrees Celsius (Alm, Walk, and Gordon, 2011, p. 114). Temperature affects the activity of the enzymes, and beyond tolerable temperature, the E. coli becomes denatured and cannot function. An experiment carried out to determine the salinity conditions that inhibit the growth of E. coli indicated no growth inhibition up to 10% salt concentration. Before experimenting, the speculation was that the E. coli cells would burst due to osmosis in low salinity conditions (Yoon and Hovde, 2008, 226). The water concentration would move from the surrounding and into the cell making it explode. In high salinity conditions, the micro-organism would lose a lot of water trying to maintain a salinity equilibrium. In contrast, E. coli can survive in salinity conditions of 0 to 10% concentration.
The varying glucose concentration up to 10 % does not affect the bacteria concentration. From previous experiments, the absence of glucose inhibits the growth of E. coli and higher concentration yield a higher level of E. coli bacteria (Yoon and Hovde, 2008, 224). The effect is as a result of the E. coli turning glucose into energy and using the power to grow the colonies.
Optimum pH levels for E. coli range from 6.5 to 11 beyond which the conditions are either too acidic or too alkaline for survival (Todar, Ubukata, and Hamada, 2005, p. 233). Enzymes in the E. coli are involved in some chemical processes that depend on optimal pH levels to occur. Extreme conditions lead to inhibition of enzymes and this results in the death of E. coli. The best working conditions are at a pH of 7.0.
Pathogenic Properties
E. coli is transmitted from cows, sheep, and goats since it exists in the gut of healthy cattle. It can be transferred when farming using animal manure (Alm, Walk, and Gordon, 2011, p. 113). Handling manure and failing to clean your hands or farm produce may lead to contamination. Drinking raw milk and eating raw unclean vegetables may cause disease of the E. coli bacteria. Water contamination with ordure or raw sewage contains E. coli (Todar, Ubukata, and Hamada, 2005, p. 227). The bacteria are harmful, and though it exists in large numbers, only ten are required to cause blood-stained diarrhea. Thus it is essential to sensitize people on maintaining high levels of hygiene to curb E. coli infection outbreaks. They should also ensure they boil milk and water before drinking to kill E. coli bacteria if present.
E. coli bacteria cause infections by releasing toxins which blind the gut lining and are notorious for causing Urinary tract Infections. They are most common in women due to their short urinary tract. Poor toilet habits dispose of the bacteria close to the urinary tract, and as a result of ‘Ascending infections' in the lower urinary tract, E. coli finds its way to other parts of the urinary tract, e.g. the Uterus and kidneys (Yoon and Hovde, 2008, 221). The symptoms include; the frequent painful passing of urine, blood stains in urine, fever and severe odor.
Treatment of infections caused by E. coli is performed using antibiotic drugs. In the recent past, excessive use of antibiotics in humans and as growth promoters in animals has led to a new breed of drug-resistant E. coli (Datsenko " Wanner, 2000, 515-516). Drugs such as Amoxicillin are obsolete; cannot be used to treat E. coli related diseases. Stronger antibiotics such as Gentamycin are useful in treatment. Scientists warn that if the bacteria continually evolve rapidly, they pose a significant threat to humans.
The use of phage therapy is an excellent way of treating the infections. Phage technology uses viruses that specifically target pathogenic bacteria and ceases them thus controlling the effects caused by E. coli. In 2006, a vaccine against E. coli o15: H7 O-polysaccharide was developed and deduced fit for children (Yoon and Hovde, 2008, 220). Its administration is for children to between two to six years.
Genetic Properties
Besides the numerous shortcomings of Escherichia Coli, it has some advantages. E. coli is significantly helping scientists study bacterial genetics. It provides essential vitamins such as vitamin K and vitamin B12 in the intestines to its host. Through genetic engineering, it is used to produce insulin. E. coli is used by analysts to determine fecal water contamination (Yoon and Hovde, 2008, 229). E. coli has made a grand contribution to the laboratory production of human insulin and Taxol; treatment for cancer and an epidermal growth factor used in the treatment of burns and wounds.
E. coli's
ubiquity enables researchers to study it as a micro-organism and representation of other bacteria (Yoon and Hovde, 2008, 220). Microbial evolutions can be reviewed and better understood in less optimal conditions in genetics and bacterial metabolism. Comprehension of the basis of bacterial environmental regulation will aid in mastery of the pathogenesis, treatment, and prevention of diseases caused by E. coli. Scientists use it with an aim to create a working computer that can be fitted into living cells to control the dominant genes in a particular organism. Unwanted genetic disorders will be eliminated from the human gene and only the hybrid disease resistant genes will be inherited.
Conclusion
The E. coli bacteria is essential in the works of biotechnology. Since the diseases it causes can be shunned, scientific research using the bacteria should proceed and people should be sensitized on the importance of good hygiene to avoid E. coli infections. Also, control measures should be put in place in order to prevent the continuous development of drug-resistant strains of the bacteria. E. coli bacteria cannot be transmitted from person to person through day-to-day activities like hugging, kissing and shaking hands. Though the bacteria are found in the intestines of humans, doctors do not recommend them since they slow down the digestive system thus diminishing the body’s ability to remove toxins. They cannot be removed completely from the gut hence the bacteria should be managed to avoid diseases.
References
.Ahmed, A., Li, J., Shiloach, Y., Robbins, J.B. and Szu, S.C., 2006. Safety and immunogenicity of Escherichia coli O157 O-specific polysaccharide conjugate vaccine in 2–5-year-old children. Journal of Infectious Diseases, 193(4), pp.515-521.
Alm, E.W., Walk, S.T. and Gordon, D.M., 2011. The niche of Escherichia coli. Population Genetics of Bacteria: a Tribute to Thomas S. Whittam pp. 107-119.
Datsenko, K.A., and Wanner, B.L., 2000. One-step inactivation of chromosomal genes in Escherichia coli K-12 using PCR products. Proceedings of the National Academy of Sciences, 97(12), pp.6640-6645.
Morales, M., Attai, H., Troy, K. and Bermudes, D., 2015. Accumulation of single-stranded DNA in Escherichia coli carrying the colicin plasmid pColE3-CA38. Plasmid, 77, pp.7-16.
Perna, N.T., Plunkett III, G., Burland, V., Mau, B., Glasner, J.D., Rose, D.J., Mayhew, G.F., Evans, P.S., Gregor, J., Kirkpatrick, H.A. and Pósfai, G., 2001. Genome sequence of enterohaemorrhagic Escherichia coli O157: H7. Nature, 409(6819), p.529.
Yoon, J.W. and Hovde, C.J., 2008. All blood, no stool: enterohemorrhagic Escherichia coli O157: H7 infection. Journal of veterinary science, 9(3), pp.219-231.
