Since heat treatment and NaCl treatment are not lethal to spores under normal conditions, these findings further confirm that ozone causes damage to the spore’s inner membrane, making the spores more sensitive to these treatments. Spores treated with ozone were also more sensitive to NaCl in plating media than untreated spores. 36 More interestingly, the authors found that spore survivors of ozone treatment exhibited increased sensitivity to inactivation by a normally minimal heat treatment. Damage to the spore’s inner membrane via oxidization can have several effects, including inability to germinate, spore death after germination, and spore lysis. Since the inner membrane of the spore is known to be a barrier to methylamine, this study demonstrated that the inner membrane was damaged by its inability to prevent methylamine from leaking through the barrier into the spore. subtilis were more easily penetrated by methylamine and germinated faster with dodecylamine. 36 confirmed that ozone causes damage to the spore’s inner membrane because ozone-treated spores of B. 35 The authors concluded that spores are not inactivated with ozone by DNA damage and that the major resistance factor of spores to ozone is the spore coat. subtilis were more easily inactivated when they were uncoated prior to ozone treatment (2) the spores did not germinate with nutrient germinants or Ca-DPA after ozone treatment and (3) germination of the spores with ozone did not cause release of DPA from the spore’s inner core. Young and Setlow 35 found that (1) when treated with ozone, spores of B. 33,34 Studies involving the inactivation of spores by oxidizing agents suggest that inactivation is a result of oxidative damage to the spore’s inner membrane. Aqueous ozone has a higher potential than most oxidizing agents to inactivate spores. Spores have been shown to be inactivated by several oxidizing agents, including chlorine dioxide, hydrogen peroxide, organic hydroperoxides, ozone, and sodium hypochlorite. Hoover, in The Diverse Faces of Bacillus cereus, 2016 Ozone

Once germination has begun and the spore coat has been compromised, the spore is weakened and vulnerable, and can be inactivated like other bacteria. After the germination process begins, the spore will take up water, swell, shed its coats, and produce one new vegetative cell identical to the original vegetative cell, completing the entire cycle. The process takes approximately 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 requires 6 to 8 hours for completion. The cortex is surrounded by the tough keratin-like protein coat that protects the spore. These two layers are surrounded by the cortex, which is made up of a thin inner layer of tightly cross-linked peptidoglycan surrounding a membrane (which used to be the cytoplasmic membrane) and a loose outer peptidoglycan layer. This wraps the DNA in the two layers of membrane and peptidoglycan that would normally divide the cell. After duplication of the chromosome, one copy of the DNA and cytoplasmic contents (core) are surrounded by the cytoplasmic membrane, the peptidoglycan, and the membrane of the septum. Dipicolinic acid is produced, and antibiotics and toxins are often excreted. Spore mRNAs are transcribed, and other mRNAs are turned off. Spores also are difficult to decontaminate with standard disinfectants or autoclaving conditions.ĭepletion of specific nutrients (e.g., alanine) from the growth medium triggers a cascade of genetic events (comparable to differentiation) leading to the production of a spore. In fact, bacterial spores are so resistant to environmental factors that they can exist for centuries as viable spores. The structure of the spore protects the genomic DNA from intense heat, radiation, and attack by most enzymes and chemical agents.

The spore looks refractile (bright) in the microscope. The spore has an inner membrane, two peptidoglycan layers, and an outer keratin–like protein coat. It contains a complete copy of the chromosome, the bare minimum concentrations of essential proteins and ribosomes, and a high concentration of calcium bound to dipicolinic acid. The spore is a dehydrated multishelled structure that protects and allows the bacteria to exist in “suspended animation” ( Fig.

The location of the spore within a cell is a characteristic of the bacteria and can assist in identification of the bacterium. Under harsh environmental conditions, such as loss of a nutritional requirement, these bacteria can convert from a vegetative state to a dormant state, or spore. tetani or botulinum) (soil bacteria), are spore formers. Some gram-positive, but never gram-negative, bacteria, such as members of the genera Bacillus (e.g., B. Murray PhD, F(AAM), F(IDSA), in Medical Microbiology, 2021 Spores

Spore biology