1. Koch’s Postulates Discovering what kind of bacterium causes a disease is a key step in developing ways to prevent or cure it. In 1876, the German physician Robert Koch used a set of diagnostic criteria now called Koch’s postulates to determine the cause of anthrax in cattle. The 4 postulates: 1.The same, specific pathogen must be identified in each animal (host) that has the disease. 2.The pathogen must be isolated from a host and grown in a pure culture, one in which no other kinds of cells are present. 3.The original disease must be produced in experimental hosts that are inoculated with the pathogen from the pure culture. 4.The same pathogen must be isolated from the experimental hosts after the disease develops in them.

2. Koch’s Germ Theory

3. Impact of Prokaryotes on Humans & the Environment Most bacteria are beneficial or benign: –Digestion: E. coli in digestive tract –Chemical recycling: conversion of organic material (N cycle) –Bioremediation: removal of pollutants from environment (oil spill) –Food: production and flavoring (cheese) Sewage Treatment Cheese production

4. Bioremediation of an Oil Spill