Pathogens and Their Characteristics
Pathogens are microorganisms that enter the body and cause disease. They are responsible for communicable diseases in both plants and animals. This page discusses the four types of pathogens and their specific characteristics.
Bacteria are very small living cells that reproduce rapidly within the body. They produce toxins that damage cells and tissues, leading to various bacterial infections.
Viruses, such as measles, HIV, and Tobacco Mosaic Virus TMV, are even smaller than bacteria. They are not cells themselves but reproduce rapidly within the host's body. Viruses live inside cells and replicate using the cell's machinery, eventually causing the cell to burst and release more viruses.
Highlight: Viral replication inside host cells and subsequent cell damage is the primary mechanism of how pathogens cause disease in viral infections.
Protists, like those causing malaria, are single-celled eukaryotes. Some protists are parasites, living on or inside other organisms and causing damage. They are often transferred to the host organism via a vector.
Fungi, such as those causing rose black spot, can be single-celled or made up of hyphae thread−likestructures. Fungal hyphae grow and penetrate human skin or plant surfaces, causing disease. They also produce spores to spread to other organisms.
Vocabulary: A vector is an organism that transmits a disease or parasite from one animal or plant to another.
How can pathogens spread? They can be transmitted through:
- Water contaminateddrinkingwater
- Air carriedasdropletsandbreathedin
- Direct contact touchingcontaminatedsurfaces
Example: The common cold virus can spread through airborne droplets when an infected person coughs or sneezes, or by touching surfaces contaminated with the virus and then touching one's face.
