12.1

• Bacilli is rod-shaped bacteria
• Cocci is spherical bacteria
• Vibrios is comma-shaped bacteria
• Spirochaetes are corkscrew bacteria
• Spirilla are spiralled bacteria
• Bacteria can be classified by their basic shapes or by their cell walls
• Gram-positive cell walls turn purple-blue
• Gram-negative cell walls turn red
• Viruses are 0.02-0.3 micrometres in diameter
• Viruses are 50x smaller in length than average bacteria
• The genetic material in a virus is surrounded by protein
• Bacteriophages attack bacteria by taking over and using them to replicate
• Bacteriophages can help to identify and treat diseases
• Protoctista are eukaryotic organisms and can be both single-celled and groups of cells in colonies
• Fungi reproduce millions of tiny spores which can spread huge distances
• If parasitic, fungi feed on living plants and animals
• Pathogenic modes of action include direct damage to host cells and producing toxins which damage host tissues
• Viruses cause direct damage to host tissues by taking over the cell metabolism and inserting viral genetic material into host DNA, making new viruses burst out of the cell
• Protoctista cause direct damage to host tissues by breaking cells open and digesting the cell contents, using it to reproduce
• Fungi cause direct damage to host tissues by digesting living cells and destroying them
• Bacteria produce toxins that may: break down cell membranes, inactivate enzymes, or interefere with host genetic material
• Some fungi produce toxins which affect host cells
• The disease triangle is made up of: a susceptible host, a conductive environment, and the pathogen