1. Gram-Negative Bacteria
Joen Lee

2. What are Gram-negative bacteria?
Gram-negative bacteria are bacteria that do not retain crystal violet dye in the Gram staining protocol.

3. Characteristics 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

4. 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

5. Example Species Proteobacteria: Escherichia coli (E. coli) Salmonella
Shigella
Pseudomonas
Moraxella
Helicobacter
Stenotrophomonas