What Do Pathogens Look Like?

Pathogens are agents that cause disease. Pathogens come in many shapes and sizes, and are often difficult to tell whether they are potentially disease-causing.

Significance

Pathogens are agents that are capable of causing disease. Pathogens generally fall into three classes: fungal, bacterial and viral (although there are some chemicals that are capable of causing disease, these diseases are generally not infectious and are therefore not pathogenic in the strict sense of the word). In each of these cases anti-fungal, anti-bacterial (antibiotics) and anti-viral medications may help to fight off the effects of the pathogens. Some pathogens are relatively easy to cure with these agents, while others are resistant and are incapable of being eradicated.

Effects

Pathogens can work in a number of different ways. A pathogen can infect and multiply within an organism, directly causing infection and illness. The flu virus is an example of such a pathogen. Other types of pathogens harm their hosts by producing toxins that promote infection and illness. An example of toxin-producing pathogens are those bacteria that produce tetanus toxins. In this case the toxin the bacteria produces is deadly, while the bacteria themselves are not.

Size

Pathogens are all very small and must be this way in order to infect living organisms. Bacterial pathogens can be large by bacteria standards but are still microscopic. While fungal infections may be caused by a visible pathogen, the individual fungal cells can also be microscopic. Many other pathogens, specifically viruses, are even smaller than bacteria and may even be unable to be seen with a standard microscope. For reference the smallest bacteria is larger than the largest virus.

Misconceptions

Not all bacteria are considered pathogenic. In fact, most bacteria either cannot cause disease or are even beneficial. Bacteria in the human digestive system are necessary for proper digestion, and cultures of these bacteria (called probiotics) are being sold in health food stores everywhere. Bacteria are also responsible for ripening cheeses and sauerkraut. Yeasts can be pathogenic but can also be responsible for fermenting sugars into alcohol and producing beer, wine and leavening bread.

Warning

Some species of bacteria and fungi are usually harmless but can become pathogenic in people with compromised immune systems. The soil bacteria Pseudomonas is an example of such a bacteria. To most of the human population this bacterium is benign, but when inhaled by someone who has cystic fibrosis, it can lead to a fatal infection.

Resources

• About Viruses