1. Producing toxins: Some bacteria produce toxins, which are poisonous substances that can damage cells and tissues. These toxins can be released into the surrounding environment (exotoxins) or released when the bacteria dies (endotoxins).

* Examples:

* Botulism: Caused by toxins produced by _Clostridium botulinum_.

* Staph infections: Can be caused by toxins produced by _Staphylococcus aureus_.

* E. coli infections: Some strains of _E. coli_ produce toxins that can cause severe diarrhea.

2. Invading and damaging tissues: Other bacteria directly invade and damage host tissues. They can multiply within cells or in body fluids, causing inflammation, tissue destruction, and organ damage.

* Examples:

* Tuberculosis: _Mycobacterium tuberculosis_ infects the lungs, causing inflammation and tissue damage.

* Pneumonia: Various bacteria can cause pneumonia by invading and multiplying in the lungs.

* Cholera: _Vibrio cholerae_ infects the intestines and causes severe diarrhea.

These are just two common mechanisms, and there are many other ways bacteria can cause disease. The specific mechanisms often vary depending on the type of bacteria involved.