E.coli

Hello guys!
Here I go again!

      Today we are going to see a little bit about a very commom bacteria, Escherichia coli, or most known as E.coli. The habitat of this microorganism is humans' intestine and animals. Most of E.coli doesn't  cause disease on their host, however some strain are able to harm. (1)

       The discover of E.coli was in 1885 by Theodor Escherich, when he isolated the bacteria from feces of newborn. Untill 1935, when a strain of E.coli was associated with diarrhea cases in infants, it was seen only as a commensal organism. (2) 

          Some characteristics of this bacteria are listed below:
       - Roden-shaped (bacilli)
       - Gram-negative - looks pink in microscopy image
       - Has LPS (Lipopolysaccharides)
       - Has flagella - permits mobility
       - Facultative anaerobe - grows in presence or absence of oxigen.
       - Belongs to Enterobacteriaceae family
       - In agar plate: colonies are circular, bege, convex.

Take a look at the pictures below, they represent the characteristics above:

Figure 1. In a microscopy magnitude of 1000x  we can see E.coli and three of its characteristics: gram-negative (pink), roden-shape and <1um size. Photographed by SMC Microbiology student Maiary Voltolini, 2014.

Figure 2. In detail, the typical gram-negative cell wall is shown. It has two plasma membrane, external and a intern one. The extarnal had attached many molecules of LPS, as well as other components. Photo from Prescott's Microbiology, McGraw-Hill Science/Engineering/Math; 9 edition (January 8, 2013), p.58.

Figure 3. Growth of E.coli in thioglycollate broth, overnight 35oC. In anoxic condition the bacteria could grow, and also it swam to get nutrients around, so we can notice the facultative anaerobe and flagela characteristic. Photographed by SMC Microbiology student Maiary Voltolini, 2014.

Figure 4. Morphology of E.coli colonies when they grow in agar plate. Circular, bege, convex. Photographed by SMC Microbiology student Maiary Voltolini, 2014.

Figure 4.  MacConkey agar containing two bacteria, one that ferments lactose (in pink) and one that doesn't (yellow) . Image from http://en.wikipedia.org/wiki/MacConkey_agar.

     Bacteria that are able to ferment lactose present in MacConkey agar are seen as pink because they

produce an acid that lowers the pH of media and results in pink coloration.   

For now that is all, next time we will see more about this bacteria. Also, in other posts, Herpes virus will be explored.

       And just for fun, a small cartoon!

Cartoon from Biology Fun Blog. (http://biologyfun.blogspot.com/)

(1) http://www.cdc.gov/ecoli/general/index.html
(2) http://textbookofbacteriology.net/e.coli.html
Prescott's Microbiology, McGraw-Hill Science/Engineering/Math; 9 edition (January 8, 2013)