Country: United States
Date: November 2008
E.coli is a gram -ve bateria. How can one diferentiate otner
bacteria that may have same color from E.coli? In other words if you
gram stain a bacteria, how do you know it's E.coli
After determining a bacterium is Gram negative, the bacterium's ability
to ferment various sugars will distinguish it from other Gram negatives.
Also, nowadays bacteria can be distinguished from each other by the
nucleotide sequence in their genes that code for ribosomal RNA.
Ron Baker, Ph.D.
There are lots of ways of classifying bacteria. Traditional microbiology lab
techniques rely on gram staining as well as other kinds of stains,
appearance under microscope (e.g. size and shape), and how colonies look
(size, shape, color, margin). You can also use indirect methods such as
changing the conditions in which they live (not all bacteria thrive in the
same conditions). More modern techniques can sequence DNA to identify not
only the species, but even different strains within the same species.
Hope this helps,
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Update: June 2012