7/23/2019 Gram Positive&Gram Negative Cells

1/1

Reyes 1

Andrea Jasmin Reyes

Fortier

BioTech 1010

Gram-Positive & Gram-Negative

Gram-positive and gram-negative bacteria vary in many characteristics First!y" gram-

positive bacteria have a thic# Peptidog!ycan !ayer" $hereas gram-negative have a thin sing!e

!ayer An o%ter membrane is a!so absent in a gram-positive" b%t present in a gram-negative

Gram-positive bacteria ce!!s a!so have a !o$ !ipid and !ipoprotein content" $here gram-negative

have a high content d%e to the presence o an o%ter membrane Another dierence is the gram

reaction Gram-positive retain crysta! vio!et dye and stain dar# vio!et or p%rp!e Gram-negative

bacteria $o%!d deco!ori'ed to accept saranin" staining the ce!! red This %se o gram staining is

the most common rom to disting%ish an %nidentiied bacteria By %sing basic stains" d%e to their

positive charge they $i!! bind to the po!ysaccharides" proteins and n%c!eic acids The ce!! $a!!s

or gram-positive bacteria have a higher peptidog!ycan and !o$er !ipid content than gram-

negative bacteria Bacteria ce!! $a!!s are stained by the crysta! vio!et dye The dye dehydrates the

thic#er gram-positive ce!! $a!!s" c!osing the pores as the ce!! $a!! shrin#s d%ring dehydration As

a res%!t" the di%sion o the vio!et dye is b!oc#ed and the bacteria stay stained