1/26/2016 endotoxins Exotoxins s(LPS)that are part of located outside the bacterial cell ted when the Proteins produced and secreted by bacteria the cell wall ly negative bacterium that produces Example:botulinum exotoxin -1 mg kills 1 million guinea pigs htheacerm Antitoxins:antibodies against specific exotoxins Endatoxine:toxint comnased Toxoids:inactivated exotoxins used in vaccines ce that are pr of the diphtheria and tetanus voccines are examples Three Main Types of Exotoxins Three Main Types of Exotoxins Membrane-disrupting toxins lyse host cells A-B toxins contain by disrupting plasma membranes ·an enzyme component -form protein channels in the membrane (A part) ·a binding component contribute to virulence by killing host cells (B part) -Leukocidins-kill phagocytic leukocytes -Diphtheria toxin orythrocytes by forming -Streptolysins-hemolysins produced by streptococci 1/26/2016 11 Lipid portions of lipopolysaccharides (LPS) that are part of the outer membrane of the cell wall of gram-negative bacteria (lipid A). The endotoxins are liberated when the bacteria die and the cell wall lyses, or breaks apart. Salmonella typhimurium, an example of a gram￾negative bacterium that produces endotoxins Endotoxins: toxins composed of lipids that are part of the cell wall Exotoxins located outside the bacterial cell Proteins produced and secreted by bacteria – Soluble in bodily fluids – Destroy host cells and inhibit metabolic functions – Many are enzymes that can act over and over – Very lethal substance – Few bacteria produce such potent exotoxins – Genes encoding toxins are found on plasmids and phages Example: botulinum exotoxin – 1 mg kills 1 million guinea pigs - Disease is due to the toxin rather than the bacterium. Exotoxin is ingested - intoxication. Antitoxins: antibodies against specific exotoxins Toxoids: inactivated exotoxins used in vaccines • diphtheria and tetanus vaccines are examples Three Main Types of Exotoxins A-B toxins contain • an enzyme component (A part) • a binding component (B part) – Diphtheria toxin Membrane-disrupting toxins lyse host cells by disrupting plasma membranes Three Main Types of Exotoxins – form protein channels in the membrane – disrupt the phospholipid portion of the membrane – contribute to virulence by killing host cells – Leukocidins—kill phagocytic leukocytes – Hemolysins—kill erythrocytes by forming protein channels – Streptolysins—hemolysins produced by streptococci