Structures contributing to virulence Flagella protein filament "tails" that allow movement and chemotaxis Vibrio cholera - 1 flagella E. coli - many flagella Shigella - no flagella Pili (fimbria) shorter than flagella and immobile allows some bacteria to adhere to their host Neisseria E. coli sex pili are special types of pili used for conjugation rather than virulence made of glycoproteins Capsules prevent phagocytosis made of polysaccharide except Bacillus anthracis, which contains D-glutamate Endospores only Bacillus and Clostridium dormant form no metabolic activity confers resistance to hot/cold, wet/dry, and host chemical defenses must autoclave to kill formed at the end of stationary phase when nutrients are in short supply dipicolinic acid may confer heat resistance Other structures Cell wall (Gram-positive) contains the major surface antigens of Gram-positive bacteria e.g. teichoic acid → activates TNF and IL-1 Mycoplasma has no cell wall Mycobacteria has unusual cell wall disruption leads to osmotic lysis Outer membrane (Gram-negative) source of endotoxin in Gram-negative bacteria Peptidoglycan structural support polymer of sugars and amino acids Plasma membrane composed of a lipoprotein bilayer Ribosome 50S and 30S subunits protein synthesis Plasmid DNA that is separate from and replicates independently of chromosomal DNA can contain genes for antibiotic resistance and toxins Periplasm in Gram-negative bacteria, the space between the outer membrane and the cytoplasmic membrane contains β-lactamases or other hydrolytic enzymes Glycocalyx polysaccharide that helps bacteria adhere to host surfaces e.g. catheter-associated infection