Endospores Characteristics and Resistance

Endospores

• Medical Importance: Two genera, Bacillus and Clostridia, produce highly resistant endospores, enabling them to survive under adverse environmental conditions for long periods.
• Characteristics: Spherical or oval, dormant or resting phase structures that can survive in soil for up to 30 years.
• Examples: B. anthracis, C. tetanus, and C. perfringens

Resistance

• Resistant to: Drying, heat, pressure, and many chemical disinfectants
• Killed by: Heating to 120°C for 15-20 minutes
• Identification: Size, shape, and location of spores within stationary phase of vegetative cells are helpful for identification
• Appearance: Appear as non-staining refractile areas within the cell

Structure of Endospores

• Formation: Stimulated by environmental conditions, such as lack of nutrients, change of temperature, and redox potential
• Stages: 3 stages of endospore formation: Activation, Germination, and Outgrowth

Germination of Endospores

• Activation: Accomplished by heating at sub-lethal but elevated temperature in vitro
• Germination: Occurs when placed in nutrients, resulting in loss of resistance to heat and chemicals, loss of calcium dipicolinate and cortex components, and degradation of acid-soluble spore proteins
• Conversion: Germination converts back to vegetative cell relatively rapidly

Outgrowth of Endospores

• Visible Swelling: Resulting from water uptake and synthesis of new RNA, proteins, and DNA
• Cell Emergence: Cell emerges from broken spore and begins to divide