Escherichia coli

From MicrobeWiki, the student-edited microbiology resource
Revision as of 18:40, 5 June 2007 by Lchueh (talk | contribs)

A Microbial Biorealm page on the genus Escherichia coli

Classification

Higher order taxa

Eubacteria (Kingdom); Bacteria (Domain); Proteobacteria (Phylum); Gamma Proteobacteria (Class); Enterobacteriales (Order); Enterobacteriaceae (Family); Escherichia (Genus)

Species

Escherichia coli

Description and Significance

E. coli was first discovered in 1885 by Theodor Escherich, a German bacteriologist. E. coli then had have been used commonly for biological lab experiment and research. E. coli is a rod shaped bacteria that can be commonly found in animal stool, lower intestines of mammals, and even on the edge of hot springs. They prefer to live at a higher temperature rather than the cooler temperatures. E. coli is a Gram-negative organism that has the disability to sporulate. Therefore, it is easy to decrease its eradicaton by simple boiling or basic sterilization. E. coli can also be classified into hundreds of strains on the basis of different serotypes. E. coli O157:H7, for example, is a well-studied strain of the bacterium E. coli, which produces Shiga-like toxins, causing severe illness by eating cheese and contaminated meat[1]. Furthermore, enteric E. coli can be classified into six categories based on its virulence properties, such as enterotoxigenic E. coli (ETEC), enteropathogenic E. coli (EPEC), enteroinvasive E. coli (EIEC), enterohemorrageic E. coli (EHEC), enteroadherent aggregative E. coli (EAggEC), and verotoxigenic E. coli (VTEC)[2]. These enteric E. coli can cause several intestinal and extra-intestinal infections such as urinary tract infection and mastitis. However, E. coli are not always harmful to human bodies or other animals. Most E. coli live in our intestines, where they help our body breakdown the food we eat as well as assist with waste processing, vitamin K production, and food absorption.



Genome structure

E. coli has only one circular chromosome, some along with an extra piece of circular plasmid. Its chromosomal DNA has been completely sequenced by lab researchers. It is well known of its proerty of gene recombinant, which is widely used as a method for further biological research. E. coli has a single chromosome with about 4,600 kb, about 4,300 otential coding sequences, and only about 1,800 known E. coli proteins. 70% of the chromosome is composed of single genes (monocistronic), and 6% is polycistronic. About 30% of the sequenced ORF's (Open Reading Frames, areas that look like they could be the start points of transcription) have unknown functions[3].


E. coli genome.png

This is a figure illustrating the comeplete genome of E. coli from National BioResource Project (NBRP).[4]


Moreover, there are many different strains of E. coli; each of these strains differs in its genotype from wild-type E. coli. The genotype will then affect the phenotype that is expressed, and further influences the physiology and lifecycle of the each strain. Therefore, different strains of E. coli can live in different kinds of animals. The natural biological process of mutation in genome is the major cuase to produce so many differnet strains of E. coli. In addition, as most bacteria do, E. coli can also transfer its DNA materials through bacterial conjugation with other related bacteria to produce more mutation and add more strains into the existing population.


Cell Structure and Metabolism

E. coli is a Gram-negative organism, which has a cell wall that consists of an outer membrane containing lipopolysaccharides, a periplasmic space with a peptidoglycan layer, and an inner, cytoplasmic membrane.[5] Even though it has extremely simple cell structure, with only one chromosomal DNA and a plasmid, it can proform complicated metabolism to maintain its cell growth and cell division.

E. coli cell.jpg

Cell structure of E. coli from Wikipedia. [6]

Ecology

Pathology

Although E. coli in human large intestine can assist with waste processing and food absorption, some strains of E. coli can cause severe infections onto most animals, such as humans, sheep, horses, dogs, etc. The one that only found in humans is called enteroaggregative E. coli. Urinary tract infection, for example, can be caused by ascending infections of urethra. Such infection can be found in both adult male and female, and some of infants can be infected as well.

E. coli O157:H7 is one of the most infective strains that can cause food poisoning. It belongs to enterohemorrhagic strain of the E. coli and can lead to bloody diarrhea and kidney failure when one gets infected by contaminated ground beef, unpasteurized milk or contaminated water. The toxin that E. coli O157:H7 produces is a Shiga-like toxin which is a rion regulated toxin that catalytically inactivate 60S ribosomal subunits of most eukaryotic cells, blocking mRNA translation and thus causing cell death.[7] Some important symptoms are diarrhea that is acute and severe, either bloody or not bloody, stoach cramping, vomiting, loss of appetite, abdominal pain, and fever. The causes can usually clear up on their own in 1-3 days with no treatment required. However, patients should avoid dairy products because those products may induce temporary lactose intolerance, and therefore make the diarrhea worse.

Application to Biotechnology

E. coli plays an important role in current biological engineering because of its manipulation and long laboratory history. It has been widely used to synthesize DNA and proteins. Most results from E. coli research can be applied to animals and human. The most useful contribution of recombinant DNA from E. coli is to use the manipulation of E. coli to produce human insuling for diabetes patients. Since E. coli has such property that it can produce human enzyme through recombinant DNA techniques, it is widely used as a very good tool to produce useful compounds or enzymes for medication. In a latest study (Apr. 2007), socientists has explored a new method to cure Alzheimer's disease (AD), which is a neurodegenerative disorder characterized by a progressive loss of cognitive function due to extra deposition of the longer form of the amyloid peptide Abeta. In this study, scientists use E. coli to enable rapid production of the antigen and its purification.[8] In other words, E. coli plays an important role to enable the rapid, continuous production and purification in large amount of human Abeta sequence by its unique expression system.


Current Research

One recent study is working on the adherent-invasive E. coli (AIEC) which can abnormally colonize the ileal mucosa of Crohn disease (CD) patients and adhere to and invade intestinal epithelial cells of CD patients. The study shows that this kind of CD-associated AIEC strain adn adhere to the brush border of primary ileal enterocytes isolated from CD patients. The adhesion of AIEC is dependent on type 1 pili expression on baterial surface and on carcinoembryonic antigen-related cell adhesion molecule 6 (CEACAM6) expression on the apical surface of ileal epithelial cells. CEACAM6 is an essential receptor for AIEC strain to adhere the ileal eithelial cells in CD patients. Moreover, this study also performs a in vitro experiments indicating that AIEC can boost its own colonization in CD patients.[9]

Another recent study

References

1. Atlanta, Ga. "Foodborne Disease Outbreak Investigation, Epidemiologic Case Study." p. 9 -17. <http://roger.ucsd.edu:80/record=b4800216 > Retrieved on 2007-5-10.

2. Parry, Sharon. " E. coli: Environmental Health Issues of VTEC O157." London; New York: Spon Press, 2002 <http://www.engnetbase.com/books/2452/tf5952_fm.pdf> Retrieved on 2007-5-11.

3. Reed, Jennifer Leanne. "Model Driven Analysis of Escherichia coli Metabolism." 2005. <http://roger.ucsd.edu/search/Xe.+coli%2C+genome&searchscope=7&SORT=D/Xe.+coli%252C+genome&searchscope=7&SORT=D&extended=1&SUBKEY=e.%20coli%252C%20genome/1%2C3%2C3%2CE/frameset&FF=Xe.+coli%252C+genome&searchscope=7&SORT=D&2%2C2%2C> Retrieved on 200-5-18.

4. National BioResource Project.<http://www.shigen.nig.ac.jp/ecoli/strain/top/top.jsp> Retrieved on 2007-5-28.

5. Wikipedia. <http://en.wikipedia.org/wiki/Image:EscherichiaColi_NIAID.jpg> Retrieved on 2007-5-28.

6. Medical Encyclopedia. <http://www.nlm.nih.gov/medlineplus/ency/article/000296.htm> Retrieved on 2007-5-20.

7. Philpott, Dana. "E. coli: Shiga toxin methods and protocols." <http://roger.ucsd.edu:80/record=b4427335> Retrieved on 2007-5-19.

8. Subramanian S, Shree AN. "Expression, Purification and Characterization of a Synthetic Gene Encoding Human Amyloid Beta in Escherichia coli.<http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=17536333&query_hl=14&itool=pubmed_docsum> Apr. 2007. Retrieved on 2007-5-25.

9. Barnich N, Carvalho FA, Glasser AL, Darcha C, Jantscheff P, Allez M, Peeters H, Bommelaer G, Desreumaux P, Colombel JF, Darfeuille-Michaud A. "CEACAM6 Acts as a REceptor for Adherent-invasive E. coli, Supporting Ileal Mucosa Colonization in Crohn Disease. May 24, 2007. <http://www.ncbi.nlm.nih.gov/sites/entrez?Db=pubmed&Cmd=ShowDetailView&TermToSearch=17525800&ordinalpos=7&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum> Retrieved on 2007-6-1.




European Journal of Biochemistry. By Federation of European Biochemical Societies. 2004

Wikipedia <http://en.wikipedia.org/wiki/Escherichia_coli#Strains>


Edited by Li Chueh, student of Rachel Larsen at UCSD.


.