Download Gram-Negative Bacteria - Mrs. Yu`s Science Classes

Gram-Negative Bacteria
Joen Lee
What are Gram-negative bacteria?
Gram-negative bacteria are bacteria that
do not retain crystal violet dye in the Gram
staining protocol.
Characteristics
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Cytoplasmic membrane
Thin peptidoglycan layer
Porins in the outer membrane
Space between the layers of peptidoglycan and
the secondary cell membrane: periplasmic
space
If present, flagella have four supporting rings
instead of two
Lipoproteins are attached to the polysaccharide
backbone
Outer Membrane
outer leaflet →
lipopolysaccharide
 endotoxin enters the
circulatory system → toxic
reaction (high temperature,
high respiration rate, low
blood pressure)
 outer membrane →
protects the bacteria from
antibiotics, dyes, and
detergents
 provides resistance to
lysozyme and penicillin
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Example Species
Proteobacteria:
 Escherichia coli (E. coli)
 Salmonella
 Shigella
 Pseudomonas
 Moraxella
 Helicobacter
 Stenotrophomonas
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