Demonstration of EndosporeĮndospores cannot be stained by ordinary methods, such as simple and Gram staining, because dyes do not penetrate the endospore wall. Bacillus anthracis and Bacillus cereusare the causative agents of anthrax and self-limiting food poisoning, respectively. tetaniare the causative agents of gas gangrene, botulism, and tetanus, respectively. botulinum (a potential agent of bioterrorism), and C. However, some species of Bacillus and Clostridium have medical significance. Most endospore-forming bacteria are found in soil or aquatic environments. Spores are not often found at the site of infection because nutrients are not limited. Spores are formed only when nutrients are insufficient. Antibiotics are ineffective against spores. Spores do not exhibit measurable metabolic activity. Wounds contaminated with soils can be infected with spores and cause diseases such as tetanus and gas gangrene. Spores can survive for many years in soil and other inanimate objects. The only solution designated as sporicidal will kill spores. Spores are highly resistant to many chemicals, including most disinfectants. Medical supplies must be heated to 121☌ for at least 15 minutes to be sterilized. Medical Importance of Bacterial Spores Important features of Spores Medical Implications Spores are highly resistant to heating spores are not killed by boiling (100☌) but are killed at 121☌. It should be noted that unlike the process of binary fission observed with vegetative cells, endospore formation is not a reproductive process but a process of differentiation that provides the bacteria with a mechanism for survival. When the free endospores are placed in an environment that supports growth, the endospores will revert to vegetative cells in a process called germination. Mature endospores are released from the vegetative cell to become free endospores. Increases or decreases in other enzymes.Ī mature endospore contains a complete set of genetic material (DNA) from the vegetative cell, ribosomes, and specialized enzymes.New enzymes (i.e., dipicolinic acid synthetase, heat-resistant catalase).The following factors/constituents play major roles in the resistance of bacterial spore: Bacterial spores are highly resistant to Resistanceīacterial spores are highly resistant to ordinary boiling, disinfectants, and heating, but spores of all medically important bacteria are destroyed by autoclaving. The final stage, outgrowth, involves visible swelling due to water uptake and synthesis of RNA, proteins, and DNA. Germination is a rapid process that involves loss of microscopic refractility of the endospore, increased ability to be stained by dyes, and loss of resistance to heat and chemicals. Activated endospores can germinate when placed in a suitable culture medium. Activation occurs when endospores are heated for several minutes at an elevated but sub-lethal temperature. This process involves three steps: activation, germination, and outgrowth. When favorable conditions prevail (i.e., availability of water, appropriate nutrients), spores germination occurs, forming vegetative cells of pathogenic bacteria. The process of conversion of a spore into a vegetative cell under suitable conditions is known as germination. In addition to the endospore’s low water content, the core’s pH is about one unit lower than the vegetative cell cytoplasm.The core of a mature endospore has only 10-25% of the water content of the vegetative cell, and thus the consistency of the core cytoplasm is that of a gel.This complex intercalates (inserts between bases) in DNA and stabilizes the DNA against heat denaturation. The calcium-dipicolinic acid complex represents about 10% of the dry weight of the endospore, thus helping to dehydrate it. Endospores are also enriched in calcium, most of which are complexed with dipicolinic acid.Dipicolinic acid, absent in vegetative cells, accumulates in the bacterial endospore’s core.The core of the mature endospore differs greatly from the vegetative cell from which it was formed. Cytoplasmic membrane, cytoplasm, nucleoid, ribosomes, and other cellular essentials are found inside the core wall. The core is the innermost region of a bacterial endospore surrounded by a core wall. The cortex lies below the spore coat and consists of loosely cross-linked peptidoglycan. The spore coat is composed of layers of spore-specific proteins. Exosporium, a thin protein covering, is the outermost layer of a bacterial endospore.
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