Living cells are known as vegetative cells; the smallest unit of life that is like a tiny factory that is constantly working to live, grow and reproduce. But vegetative cells are vulnerable to damage from many environmental forces.
A few types of cells have a special trick up their sleeve that allows them to go dormant when environmental conditions become inhospitable. The trick is the ability to form spores. Some bacteria can form resistant bodies called endospores; structures that can weather the hostile conditions that kill vegetative cells.
* What Is a Bacterial Endospore? *
Endospores are dormant bodies produced only by certain genera of bacteria, namely members of Bacillus, Clostridium and Sporosarcina. These types of bacteria essentially have two phases to their life cycle, vegetative cells and endospores.
When the living, vegetative cells of these genera are exposed to harsh environmental conditions, they undergo a process called sporulation and ultimately generate endospores. As one of the hardiest life forms, endospores are able to withstand high temperatures, drying out, freezing, radiation, chemicals and many other environmental conditions that would easily kill a vegetative cell.
Endospores are metabolically inactive, like a seed that is able to wait for the environment to again become favorable. Once environmental conditions improve, the endospore then germinates back into a living, vegetative cell that can grow and thrive.
* Medical Impact of Bacterial Spores *
Although only a few groups of bacteria are able to form spores, people do frequently come in contact with them. Many types of soil bacteria produce these dormant structures, so if you garden or otherwise play in the dirt dirt, you’ll definitely come in contact with bacterial spores. But you don’t have to get dirty to be exposed to spores, they are everywhere in the environment, even in health care settings.
Luckily, most endospore-producing bacteria are non-pathogenic microbes that are no threat to humans. There are, however, some medically significant endospore producers that cause serious infectious disease.
* Disease Caused by Bacillus *
Bacillus anthracis is the causative agent of anthrax. Although people are most familiar with anthrax as a form of bioterrorism, this bacterium is naturally found in the soil, and those working with livestock are at higher risk of exposure than is the general public.
* Diseases Cause by Clostridium *
Although Clostridium bacteria are killed by exposure to oxygen, their endospores, once introduced into the human body, can germinate and cause infection. Clostridium tetani is the agent of tetanus. C. perfringens can cause gas gangrene. C. botulinum produces the botulinum toxin that causes botulism, a deadly form of food poisoning. Another member of this genus, Clostridium difficile, or C. diff, is currently a very problematic bacterium, resistant to many antibiotics. C. diff can result in a serious, potentially deadly infection of the colon called pseudomembranous colitis.
* Medical Control of Endospore Producers *
Because these genera can form endospores, they are difficult to eliminate from health care environments where sterility is so important. There are vaccinations and antibiotics used to prevent or treat infections caused by some endospore producers, but these measures do not work in all cases, particularly when the infection resides deep in tissues. The treatment for gas gangrene is extreme; debridement or amputation.
* Sources *
Bauman, R. (2005) Microbiology. Pearson Benjamin Cummings.
Park Talaro, K (2008) Foundations in Microbiology. McGraw Hill
