Some examples of pathogenic bacteria are Bacillus anthracis, Escherichia coli, Mycobacterium tuberculosis, Salmonella and Vibrio cholerae. These particular pathogens are easily transmitted through water, and prior to modern water treatment methods, were capable of rapid transmissions throughout entire populations, which resulted in hundreds of deaths. One of the deadliest pathogens is Mycobacterium tuberculosis, which continues to result in around 2 million deaths worldwide each year, most of which occur in sub-Saharan Africa.
Pathogenic bacteria thrive in temperatures between 68 and 104 degrees Fahrenheit, a range which can be accommodated by the normal human body temperature of 98.6 degrees. When pathogenic bacteria attach themselves to human host cells, they can cause direct damage while they use those cells as a nutrient source. The multiplication of bacteria within host cells can also cause the cellular membranes to burst.
One of the harmful effects caused by pathogenic bacteria can come from the toxins they produce. Certain proteins, called exotoxins, are produced as part of their normal metabolic processes. The exotoxin produced by Clostridium botulinum, for example, is one of the deadliest poisons known. A quantity of 1 milligram of the lethal botulinum exotoxin has been demonstrated to be sufficient to kill 1 million laboratory test animals. In certain diseases, the harm caused by pathogenic bacteria is not caused by the bacteria themselves, but is instead a result of the exotoxins they produce.