Country: United States
Date: January 2009
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
NEWTON BBS does not recommend growing/culturing bacteria without the
supervision of a microbiologist, and a properly equipped microbiology
laboratory. Safety is our main concern! Growing dangerous bacteria
species unknowingly is a real possibility and serious illness may occur
without proper handling techniques. Furthermore, without proper bacterial
disposal procedures such as an autoclave can guarantee, there is a danger
to anyone who comes in contact after disposal.
You don't! If one is a very experienced microbiologist, sometimes bacteria
have certain shapes that are unique. But, most gram negative bacteria look
very similar. The only way to know for sure if its E coli is to grow it out
on media and do biochemical testing to confirm it.
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