Endospore
As an endospore is called a Überdauerungsform formed within an organism or a cell, which differentiates it from the exospores.
Endospores in bacteria
Education
Some Gram- positive bacteria form in response to a state of hunger endospores. A lack of guanine nucleotides in the cytoplasm also initiates a Stomata ( uneven) division of the protoplasts in the cell wall and subsequent endocytosis -like process, which forms the spore. In contrast to most other spores are in endospores mostly not about reproductive forms, because each cell usually forms only one endospore and their release perishes, only in rare cases (for example Anaerobacter polyendosporus ), several (up to seven) endospores formed.
Known Endosporenbildner are many species of the genera Bacillus and Clostridium, in particular Bacillus anthracis ( anthrax ), Clostridium botulinum ( botulism ) and Clostridium tetani (tetanus ). However, other genres, such as Desulfotomaculum, Sporolactobacillus Sporosarcina and Thermoactinomyces form endospores can. They all belong to this division Firmicutes.
Other Endosporenbildner genera are:
- Acetonema, alkaline Bacillus, Ammoniphilus, Amphibacillus, Anaerobacter, Anaerospora, Aneurinibacillus, Anoxybacillus
- Brevibacillus
- Caldanaerobacter, Caloramator, Caminicella, Cerasibacillus, Clostridiisalibacter, Cohn Ella
- Dendrosporobacter, Desulfosporomusa, Desulfosporosinus, Desulfovirgula, Desulfunispora, Desulfurispora
- Filifactor, Filobacillus
- Gelria, Geobacillus, Geosporobacter, Gracilibacillus
- Heliobacterium, Heliophilum
- Lentibacillus
- Mahella, Moor Ella
- Oceanobacillus, Ornithinibacillus, Oxalophagus, Oxobacter
- Paenibacillus, Paraliobacillus, Pelospora, Pelotomaculum, Piscibacillus, Ponti Bacillus, Propionispora
- Salinibacillus, Salsuginibacillus, Sporacetigenium, Sporoanaerobacter, Sporobacter, Sporobacterium, Sporohalobacter, Sporomusa, Sporotalea, Sporotomaculum, Syntrophospora
- Tenuibacillus, Tepidibacter, Terri Bacillus, Bacillus Thalasso, Thermoacetogenium, thermal alkaline Bacillus, Thermoanaerobacter, Thermoanaeromonas, thermal Bacillus, Thermovenabulum, Tuberibacillus
- Virgibacillus, Vulcanobacillus
Properties
The endospore as a resting stage can last long time; as viable spores were found in the stomach of a preserved in amber bee, which are more than 25 million years old. However, it is discussed whether the material was contaminated with recent endospores. But it is clear that endospores can survive for very long time. A metabolism can not be proved ( cryptobiosis ).
The endospores formed by bacteria exhibit a high resistance to heat, cold, dehydration, different types of radiation, chemical agents, lysozyme and extreme pH values . They can hardly be dyed with conventional methods. The resistance is based on a multilayer shell and the low water content. Impermeability of the spore coat of radiochemical products and bonding of free radicals by sulfur-containing constituents impart resistance against radioactive radiation. The spores contain Calciumdipicolinat, a characteristic substance which is not present in vegetative cells. The DNA of endospores is protected by SASP (small acid soluble [ spore ] protein).
Germination
From endospores can emerge stages of development of bacteria under certain environmental conditions again active ( " vegetative "). From a Endospore thereby a single-celled bacterium developed. There are three phases: first, in most cases, the endospore must be enabled. Activation is likely to substantially increase the permeability of the spore coat, so that material inductors ( signal substance ) of the spore can penetrate from the outside. This can be done by aging ( promoted by high temperatures ) or by mechanical damage. If certain after this phase of activation, species-specific inducers in the outdoor environment are present, germination in the narrow sense (English germination ) is initiated. As Keimungsinduktoren act such substances, which are present when conditions in the natural environment in general, which are favorable for the growth of bacteria. Examples of these are caused by the bacterium usable energy sources (eg, glucose), and nutrients (such as adenosine and L- alanine). In germination, the spore coat is weakened by partial degradation. When outgrowth (English outgrowth ) takes the cell through water uptake and growth (formation of new cell components ) in volume, explodes the spore coat and forms a new cell wall.