How Long Can spores be viable?
Spores are metabolically inactive and dehydrated. They can remain viable for thousands of years. When spores are exposed to favorable conditions, they can germinate into a vegetative cell within 90 minutes.
Germination of spores into the vegetative state is stimulated by disruption of the outer coat by mechanical stress, pH, heat, or another stressor and requires water and a triggering nutrient (e.g., alanine). The process takes approximately 90 minutes.
More than 90 percent of spores could be “resurrected” after heating to 300o C, and about 40 percent after being heated to 420o C.
Spores can also survive for 2 years in water, 10 years in milk and up to 71 years on silk threads. Vegetative organisms are thought to be destroyed within a few days during the decomposition of unopened carcasses.
Spores are metabolically inactive and dehydrated. They can remain viable for thousands of years. When spores are exposed to favorable conditions, they can germinate into a vegetative cell within 90 minutes.
BACTERIA | Bacterial Endospores
Moreover, spores are extremely dormant and may survive thousands of years in the wet state. The mechanisms contributing to resistance and dormancy are manifold. One of the key factors is the unusual spore structure that is formed during sporulation.
A process called sterilization destroys spores and bacteria. It is done at high temperature and under high pressure. In health care settings, sterilization of instruments is usually done using a machine called an autoclave.
In addition to the well-known activation at 65 C for 45 min, spores were also activated by exposure to 34 C for 48 hr. The activation by heat and by reducing agents was reversible; the reverse reaction was temperature-dependent.
When mold spores drop on places where there is excessive moisture, such as where leakage may have occurred in roofs, pipes, walls, plant pots, or where there has been flooding, they will grow. Many building materials provide suitable nutrients that encourage mold to grow.
Spores exhibit greatly increased resistance to a large number of agents, including desiccation, freezing, thawing, elevated temperatures in either the wet or dry state, UV and γ-radiation, high pressures, and a huge number of toxic chemicals with a variety of nasty effects including oxidizing agents, alkylating agents, ...
What type of conditions do spores need to grow?
Spore germination requires the presence of water and oxygen and is characterized by rapid swelling as a result of hydration.
We tested the hypothesis that thermospores remain viable after freezing at temperatures as low as −80°C, and that different temperature pretreatments furthermore select for a greater diversity of germinating endospores during subsequent incubation at high temperature permissive to thermophile germination and growth.
Gottlieb, for example, writes, "... a spore is dormant when it does not germinate under the same nutritive and environmental influences which later allow production of germ tubes."
If shielded against solar ultraviolet (UV)-radiation, up to 80 % of spores in multilayers survive in space. Solar UV-radiation, being the most deleterious parameter of space, reduces survival by 4 orders of magnitude or more.
Spore prints should be stored in a very dry and completely sterile container and refrigerated. Humidity is the enemy of spore prints so make sure your packaging is sealed tightly and in a dry environment. Many spore curators have filing systems similar to the old card catalogues found in libraries.
If a spore is faced with unfavourable conditions, such as lack of nutrients, low temperature, an unfavourable pH or the presence of an inhibitor (for example, on a surface of a plant), the spore remains dormant and delays germination.