Bacterial structures

Flagellum Proteins. Motility.
Pilus/fimbria Glycoprotein. Mediate adherence of bacteria to cell surface; sex pilus forms during conjugation.
Specialized structures    
Spore Keratin-like coat; dipicolinic acid; peptidoglycan, DNA. Gram ⊕ only. Survival: resist dehydration, heat, chemicals.
Cell envelope    
Capsule Organized, discrete polysaccharide layer (except poly-d-glutamate on B anthracis). Protects against phagocytosis.
Glycocalyx Loose network of polysaccharides. Mediates adherence to surfaces, especially foreign surfaces (eg, indwelling catheters).
Outer membrane Outer leaflet: contains endotoxin (LPS/LOS).

Embedded proteins: porins and other outer membrane proteins (OMPs)

Inner leaflet: phospholipids.

Gram ⊝ only.

Endotoxin: lipid A induces TNF and IL-1; antigenic O polysaccharide component.

Most OMPs are antigenic.

Porins: transport across outer membrane.

Periplasm Space between cytoplasmic membrane and outer membrane in gram ⊝ bacteria. (Peptidoglycan in middle.) Accumulates components exiting gram ⊝ cells, including hydrolytic enzymes (eg, β-lactamases).
Cell wall Peptidoglycan is a sugar backbone with peptide side chains cross-linked by transpeptidase. Net-like structure gives rigid support, protects against osmotic pressure  damage.
Cytoplasmic membrane Phospholipid bilayer sac with embedded proteins (eg, penicillin-binding proteins [PBPs]) and other enzymes. Lipoteichoic acids (gram ⊕ only) extend from membrane to exterior. Site of oxidative and transport enzymes; PBPs involved in cell wall synthesis. Lipoteichoic acids induce TNF-α and IL-1.

Filipino MD

An independent organization catered to bringing enriching opportunities to doctors, researchers and medical institutions.


Like Us On Facebook

Facebook Pagelike Widget

You cannot copy the contents of this page.