Escherichia Coli(E. Coli)By: Emma Stern


e-coli-streptococci.jpeg









(shwetha)

Classification:

Kingdom: BacteriaPhylum: ProteobacteriaClass: Gamma ProteobacteriaOrder: EnterobacterialesFamily: EnterobacteriaceaeGenus: Escherichia
Species: Escherichia Coli

E. Coli is a rod-shaped bacterium that is usually found in the lower intestinal area of warm blooded organisms. They are mainly responsible for food poisoning and food recalls.(6) (Shwetha)
E. coli bacteria are prokaryotic, meaning that they do not have a nucleus. Instead, their DNA is a continuous chromosome in the cytoplasm in the shape of a ring which is called a plasmid. (6)(KG)



Relationship to Humans:

Normally, Escherichia Coli or E.Coli, lives in a mutualistic relationship with humans, however that can quickly change. The human body houses E. Coli in the colon where is provides nutrients, shelter and warmth. In return the E. Coli produces Vitamin K and Sodium. However, there are many different strains of E. Coli that can be very negative.
Because E. Coli DNA is suspended in the cytoplasm, the cell can easily take up extraneous DNA and/or RNA fragments and add them to their genome. This makes E. Coli an ideal laboratory specimen for studying genetic mutation and DNA experiments.(6)(KG)

The pathogenic strains of E. Coli (those that can make you sick) can cause diarrhea, urinary tract infections, respiratory illness, pneumonia, and more. Very young children and the elderly are more likely to develop severe illnesses than people of other ages, though even older children and adults who are perfectly health can become ill from E. Coli. About 5-10% of people infected with E. Coli develop hemolytic uremic syndrome (HUS), a potentially life-threatening complication that can lead to kidney failure and other serious issues. Consumption of contaminated food, unpasteurized milk, or water that has not been disinfected can result in E. Coli exposure and contraction.
(JLev)
It can also be the cause of urinary infections such as UPEC or Uropathogenic E. coli where it has mutualistic relationship or in other word it does not disturb the host. It can become infectious when people do not clean their feces properly.For example females can get infections in the uterus if they do not wipe their feces in the correct direction and males can get this infection by having sex with females who have UPEC. It can spread from the urethra to urinary tract to the bladder to the kidneys or in the males, the prostate ( part of the male reproductive system)(10) (NC).

E. Coli has become one of the model organisms used in scientific studies becaused of its short life cycle, rapid reproduction cycle, and its easy to maintain ideal environment, in a labratory setting. E Coli. has been said to be the most well known organism on the face of the planet. Humans understand E. Coli better than we understand humans.(11)(BS)

Recently many highly publicized studies have been produced that have linked E. Coli to high rates of colon cancers and have also shown evidence of a possible treatment of prostate cancer with E. Coli. Think link between colon cancer and E. Coli appears to be much more correlated and many studies have shown this but a few studies conducted have shown that E. Coli and possinbly salmonella may be used to treat several types of organ cancers. These treatments are still very much in the experimental phase and only small amounts of progress has been made on pursuing it as a treatment option. ([1] ) (DA)

Recently, it has been discovered that E. Coli can efficiently break down phytic acid and release phosphate molecule which subsequently bind to uranium. Simply put, E. Coli may be an effective way to clean up nuclear waste. (5) (SJ)

Another amazing use of E. coli is in the development of artificial human growth hormone (HGH). Biologists have successfully learned how to genetically engineer E. coli by editing its genome sequence so that they continuously produce HGH (simply a protein), creating a limitless supply of this vital hormone for humans.[2] (DM)




















E. Coli 0157[3] (SM)


Habitat and Niche:

The habitat of E. Coli, is the human gastrointestinal tract. The niches of E. Coli depend specifically on the nutrient value in the intestines and therefor greatly vary.

Additionally, E. Coli can be found in animal feces, or even next to hot springs. These bacteria prefer warm temperatures. (2) (SJ)

Although not much is known about E. Coli’s specific niches, what is generally understood about them can be described through Freter’s Nutrient-Niche theory. This theory states that the specific organism’s niche is based upon the nutrients that are available within the host organism. There is such a wide variation of nutrients that are present in the intestines, that there are so many different niches that E. Coli can colonize ([4] ) (E.S.S.).

Predator Avoidance:

There are many different ways that the bacteria E. Coli uses to avoid their predators. One way is by using their flagella, a tail located at the end of its body that is used to move or "swim" away from predators. Another way E. Coli competes with other organisms is with its cellular metabolism called chemotaxis. This helps E. Coli take in nutrients, no matter the concentration level.

Nutrient Acquisition:

E. Coli is a heterotrophic organism that gets its nutrients from a host organism. They get their nutrients through biosynthesis of nutrients that the host organism has taken in. They also take in many glucose molecules that are ingested through a 3 step central metabolism process. It also converts its pyruvates into ATP through fermentation, which allows it to be high energy and maintain itself.

Excess glucose in the small intestine may be available for e. coli consumption, which would cause them to grow at a faster rate. Salt is absorbed in the host's colon, but E. coli would utilize the excess salt. The amount of salt that E. coli attains is dependent on how much salt the host consumes. (6) (JLau)

Reproduction and Life Cycle:

Because E. Coli is a bacteria and there is no genetic material being transferred when reproducing, it reproduces by means of asexual reproduction, and basically creating clones. There is an additional process that takes place, which is called conjugation. Conjugation is the transfer of genetic material through sex pili not gametes. The only purpose of conjugation is to create some diversity between bacterium. Finally, E. Coli has a factor called plasmid that allows the conjugation to take place. The plasmid sends out signals saying that it is ready to reproduce, and theses signals attract other bacterium.

Growth and Development:

Though E. Coli, does not grow much, it uses all the nutrients it takes in in order to maintain its life. Also it develops on the mucus or epithelium on the walls of the intestine, if it can not make it there, it will not grow and therefore not survive.

The growth of E. Coli is dependent on the resources of nutrients present. If nutrient resources are steady, the bacteria will grow in a constant matter until it reaches mitosis. E. Coli best grows at 37 C, but artificial strains can exist to temperatures no higher than 49 C. Redox, pertaining to the oxidation of pyruvic acid, formic acid, hydrogen, and amino acid and reduction of substrates, drive the aerobic and in cases anaerobic respiration of the organism. (AWC)

Integument:

Escherichia coli is a gram-negative bacillus, or rod-shaped, bacteria. Since it is gram negative, it has both a peptidoglycan cell wall along with a phospholipid bilayer with membrane-spanning proteins. The outer phospholipid bilayer contains lipopolysaccharides, porin channels, and murein lipoprotein, increasing their pathogenicity. The outer membrane in the gram-negative Escherichia coli contains an endotoxin as well as an O-antigen on the lipopolysaccharides that coat the cell surface. (3) (BB-V)

Movement:

external image Flagellar%20Locomotion%20in%20E.%20coli.jpg[5] (JF)
E. Coli moves through its use of its petrichious flagella. Petrichious flagella are found on a lot of bacteria and the flagella is located all around the body of the organism. The bacteria utilizes its flagella by moving it in the counter clockwise direction, because if used in the clockwise direction, it would not get anywhere except for in circles. The flagellum also helps the bacteria latch on to other organisms or areas.

The "swimming" of the E. Coli is most common when the cell is approaching a chemoattractant, such as food. The "tumbling" of the cell is more common as the bacteria moves away from the food. To keep themselves in areas of a high concentration of food, the bacteria uses a combination of the two types of movement. (7) (WSS)

The structure of the flagella is what allows it to move. The flagella consists of microtubules arranged in a 9+2 formation, with 9 pairs of fused microtubules on the outside and one pair of unfused microtubules in the middle. Between each pair of fused ones, there are protein motor molecules called dynein arms. Using ATP as a source of energy, the dynein arms of one microtubule grip an adjacent pair, pull, release, and then bind again. This action causes the microtubules to bend and the flagella also bends, generating movement for the cell. (9) (AA)

Sensing the Environment:

E. Coli can sense a change in the chemical composition around it and it can send electrical signals to the rest of the body to tell it to move. It can also tell when the concentration of areas in the tract are high or low in certain nutrients and it uses this to obtain the greatest amount of nutrients.

Although the E.coli has a simple cell structure with one chromosomal DNA and a plasmid, certain properties help the bacteria under stressful conditions. E. coli is a rod-shaped bacteria with a cell wall that contains an outer membrane, a periplasmic (between two membranes) space, and an inner, cytoplasmic membrane. Some strains are capable of accepting and transferring plasmid, single molecules of DNA, to and from other bacteria, this helps the E.coli under stressful conditions. If it's DNA is degenerating it is capable of pulling from other DNA to compensate. (2) (PS)




Gas Exchange:

Because E. Coli is a single celled organism, all of its gas exchange occurs across their membrane.

The process by which gas exchange occurs through the membrane is called diffusion. Molecules from an area of high concentration tend to move towards areas of lower concentration. Diffusion occurs when there is a concentration gradient (a region with differences in concentration) between the two sides of the cell membrane. For example. when there is excess hydrogen gas inside the E. Coli and few hydrogen gas molecules outside of the cell membrane, the hydrogen gas molecules will pass through the cell membrane to flow from inside the cell to the outside environment. [4] (AY)


Diffusion is the movement of molecules from a region of greater concentration to a region of lesser concentration, in the direction following the concentration gradient. In living systems, the molecules move across cell membranes, which are continuously moistened by fluid.

Waste Removal:

Bacteria, such as E. Coli, secrete their waste through active diffusion through the cell membrane or their cell walls.

Environmental Physiology:

Temperature: 37 Degrees Celsius

Salt: no amount of salt inhibits the growth of E. Coli but it can tolerate up to 10% concentration

Internal Circulation

Additionally, e. coli is part of the common microflora in the large intestine and is accustomed to a pH of 7-8, which makes it suitable for the e. coli to thrive. (6) (JLau)

Review Questions

1) Even though E. coli reproduce asexually, they are able to maintain genetic diversity. How does this happen and why is this important for E. coli as a species? (FZ)
2) What properties unique to E. coli allow it to live under stressful conditions, even though its cell structure is very simple? (MC)
3) How are E. coli able to move? Why is this movement important to their survival? (LC)
4) Explain one way E. coli is helpful for humans and one way it is deleterious. (BH)

5) Explain how E. Coli is able to sense stimuli in its environment. (CC)
6) Does E. coli use exocitosis to remove waste? (MDS)
7) What chemicals do E.Coli secrete that cause for food poisoning?
8)
What mechanism does E. coli use to secrete their waste?
  1. ^ http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1479838/
  2. ^ http://www.nature.com/nature/journal/v293/n5831/abs/293408a0.html
  3. ^

    https://www.youtube.com/watch?v=3ps_Kw4EX7A
  4. ^

    http://bioweb.uwlax.edu/bio203/s2008/moder_just/habitat.htm
  5. ^

    https://www.qiagen.com/geneglobe/pathwayview.aspx?pathwayID=184