Hemolytic Analysis

Hemolytic Analysis

     In our experiment this week, we conducted hemolysis blood agar tests on our soil microbes and controls. This tests specifically determines a bacteria's ability to lyse red blood cells by the production of metabolites, called hemolysins. Hemolysins are lipids and proteins that cause the lysis of red blood cells by either forming pores in the phospholipid bilayers, or hydrolyzing phospholipids in the cell membrane. There are three different forms that constitute hemolysis. The first is Alpha-hemolysis. This occurs when bacteria reduce the hemoglobin from red bloods cells into methemoglobin. In blood agar, this result is exemplified by a dark black color, or "bruising", surrounding bacterial colonies. Beta-hemolysis is considered "true" lysis of the cells. The bacterial colonies and their surroundings are colored a light yellow color when held up to transmitted flight indicating complete degradation of red blood cells. Gamma-hemolysis indicates there is no reaction with the blood cells at all. There is no bruising or degradation.
     When bacteria have hemolytic capabilities, it can potentially heighten their virulency. Being hemolytic means having the capability to lyse red blood cells, one of the primary components of our cardiovascular system. If hemolytic bacteria were to become pathogenic and infect a human, then they would continually lyse blood cells which would initiate different symptoms and could potentially be lethal.
     We would not expect our soil microbe to be hemolytic because this ability is usually seen in pathogenic bacteria as a virulence factor. Because this bacteria may thrive more in soil and not in a living being it would drake sense that it doesn't have the need to produce hemolysins necessary to lyse red blood cells.
     The results from our blood agar tests showed that our soil microbe is alpha-hemolytic. There was bruising around the colonies in the blood agar, but when held up to the light there there was no complete lysis of blood cels in medium. This suggests that our microbe possesses some form of hemolysin metabolite that reduces the hemoglobin from the blood cells. Our control microbes produced the expected results and gave a great comparison for our soil microbe. This test gives some contradiction in determining the identity of our microbe. Corynebacterium and Lactobacillus genuses were the ideal candidates for our soil microbe, however, our blood agar results indicate that we must have some kind of Streptoccocus. 

S. aureus

S. epiderdimis

Unknown Soil Microbe

Chalmeau J, Monina N, Shin J, Vieu C, Noireaux V (January 2011). "α-Hemolysin pore formation into a supported phospholipid bilayer using cell-free expression". Biochim. Biophys. Acta 1808 (1): 271–8. 

http://textbookofbacteriology.net/pathogenesis_4.html

http://www.microbelibrary.org/component/resource/laboratory-test/2885-blood-agar-plates-and-hemolysis-protocols