Living Things - Microorganisms and Disease

Microorganisms are tiny living organisms that are invisible to the naked eye and require a microscope to be seen. Major groups include Bacteria, Viruses, Fungi, and Protists.

Pathogens are 'germs' or harmful microorganisms that cause infectious diseases. Common examples include the Influenza virus and the bacterium $Salmonella$.

Microorganisms require specific conditions to grow and multiply: warmth (optimal temperatures often between $20^{\circ}C$ and $40^{\circ}C$), moisture ($H_2O$), and a food source like glucose ($C_6H_{12}O_6$).

Many microorganisms are beneficial. For example, yeast is a fungus used in baking that undergoes fermentation: $C_6H_{12}O_6 \rightarrow 2C_2H_5OH + 2CO_2$. The $CO_2$ gas causes bread to rise.

Decomposers are microorganisms that break down dead organic matter, recycling nutrients back into the ecosystem.

Prevention of disease involves hygiene practices, vaccinations, and food safety techniques like pasteurization, where milk is heated to $72^{\circ}C$ to kill harmful bacteria.

Microorganisms are measured in micrometers ($\mu m$), where $1 \mu m = 10^{-6} m$.