Escherichia Coli Research Paper

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Escherichia coli is a Gram-negative rod that was tested on ten different biochemical testing procedures. The Escherichia coli culture on the MacConkey agar had growth and experienced fermenting of lactose (color change to yellow). This is an expected result because this agar only grows Gram-negative bacteria so it is a selective media. The bile salts and crystal violet are the agents that make the agar select against Gram- positive species. The pink tint is probably from the precipitation of bile salts. The Bacillus subtillis is a Gram-positive bacterium so it was not supposed to show growth or fermentation, but it showed growth without a color change (no lactose fermentation). This was due to the over streaking of maybe Escherichia coli or Enterococcus durans, which are Gram-negative species. Staphylococcus epidermis had a growth along with a yellow to orange color change. Media too was clear.

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