Why are endospores so resistant to antimicrobial treatments?
Endospores are very resilient structures unique to specific bacteria. Since they are used as a sort of survival system by bacteria, they are resistant to many different and extreme conditions. Endospores can survive in environmental conditions that would normally kill the bacteria, including: High temperatures; High UV radiation; Desiccation (drying out)
How do endospores survive without nutrients?
Endospores are more resistant to ionizing radiation of the same species, possibly due to reduced availability of water in the spores for hydrolysis of water and also the condensed nature of the bacterial chromosome within the spore. Clostridium botulinum spores have relatively high D 10 values that range from 1.29 to 3.34 kGy (Anellis and Koch, 1962).
What are endospores?
Bacterial endospores are more resistant to disinfectants than are vegetative organisms due to their lower water content and slower metabolism. Not all …
What are thermo-resistant endospores?
-a dormant cell that survives harsh conditions Why are endospores resistant to heat and chemicals? due to a tough outer coating made of a protein called keratin, its DNA protective proteins and its dehydrated state. Why must extreme measures be taken to stain endospores? The keratin in the spore coat resist staining
Why are endospores most resistant?
General Concepts in Disinfection Efficacy Bacterial endospores are more resistant to disinfectants than are vegetative organisms due to their lower water content and slower metabolism.
Why are endospores resistant to antibiotics?
Bacterial endospores are resistant to antibiotics, most disinfectants, and physical agents such as radiation, boiling, and drying. The impermeability of the spore coat is thought to be responsible for the endospore's resistance to chemicals.
Are endospores the most resistant?
Endospores are considered the most resistant structure of microbes. They are resistant to most agents that would normally kill the vegetative cells from which they formed.Jan 3, 2021
Why are endospores resistant to staining?
Because of their tough protein coats made of keratin, spores are highly resistant to normal staining procedures.
Why the spore endospore of a bacterium is more resistant to Sterilisation?
Therefore, any organism which produces catalase can have an increased tolerance to the effects of hydrogen peroxide. Bacterial endospores show a high degree of resistance to hydrogen peroxide due to the presence of catalase in the spore' s coat layer (Checinska et al., 2012).
What is the function of an endospore in some bacteria quizlet?
A bacterial endospore is a structure formed within a bacterium that is resistant & dormant. The endospore's purpose is to protect the bacterium from poor or unfavorable conditions that hinder its survival. Spores are also resistant to heat & chemicals that would otherwise kill other bacteria.
What are endospores and why are they of concern to healthcare facilities?
Endospores are a resistant, dormant, survival form of bacteria. They are resistant to high temperatures, most disinfectants, low level radiation and drying.
Why are spores more resistant to environmental stresses?
Spores resist numerous stress factors efficiently, including extreme heat, starvation, treatment with chemicals and radiation and are able to germinate even after long periods of dormancy [1][2][3] [4] . This high resistance to environmental stress is due to their particular and partitioned structure [5]. ...
What are three advantages of endospore formation?
From a bacterium's perspective, what are the advantages of endospore formation? - endospores are highly resistant to radiation and heat. - the endospore provides protection in dry conditions. -the endospore is more resistant to disinfectants.
How are the differences between the endospore and the vegetative cell highlighted in the endospore staining procedure?
Decolorized vegetative cells take up the counterstain and appear pink; endospores are light green. After staining, endospores typically appear as light green oval or spherical structures, which may be seen either within or outside of the vegetative cells, which appear pink.
Why do bacteria form endospores?
Endospore Formation and Structure. Endospores are formed in response to unfavorable growth conditions in the bacterial environment, most commonly induced by the limitation of nutrients. Sporulation, however, is not the first response of the bacterial cell to nutrient depletion.
What are endospores resistant to?
Bacterial endospores are resistant to antibiotics, most disinfectants, and physical agents such as radiation, boiling, and drying. The impermeability of the spore coat is thought to be responsible for the endospore's resistance to chemicals. The heat resistance of endospores is due to a variety of factors: 1 Calcium dipicolinate, abundant within the endospore, may stabilize and protect the endospore's DNA. 2 Small acid-soluble proteins (SASPs) saturate the endospore's DNA and protect it from heat, drying, chemicals, and radiation. They also function as a carbon and energy source for the development of a vegetative bacterium during germination. 3 The cortex may osmotically remove water from the interior of the endospore and the dehydration that results is thought to be very important in the endospore's resistance to heat and radiation. 4 Finally, DNA repair enzymes contained within the endospore are able to repair damaged DNA during germination.
What is the heat resistance of endospores?
The heat resistance of endospores is due to a variety of factors: Calcium dipicolinate, abundant within the endospore, may stabilize and protect the endospore's DNA. Small acid-soluble proteins (SASPs) saturate the endospore's DNA and protect it from heat, drying, chemicals, and radiation.
What is an endospore?
Unsourced material may be challenged and removed. An endospore is a dormant, tough, and non-reproductive structure produced by some bacteria in the phylum Firmicutes. The name "endospore" is suggestive of a spore or seed-like form ( endo means within), but it is not a true spore (i.e., not an offspring). It is a stripped-down, dormant form ...
How long do endospores last?
Endospores enable bacteria to lie dormant for extended periods, even centuries. There are many reports of spores remaining viable over 10,000 years, and revival of spores millions of years old has been claimed.
Which organism has been extensively studied for endospore formation?
As a simplified model for cellular differentiation, the molecular details of endospore formation have been extensively studied, specifically in the model organism Bacillus subtilis. These studies have contributed much to our understanding of the regulation of gene expression, transcription factors, and the sigma factor subunits of RNA polymerase .
How many endospores are there in Bacillus subtilis?
The spore coat, which acts like a sieve that excludes large toxic molecules like lysozyme, is resistant to many toxic molecules and may also contain enzymes that are involved in germination. In Bacillus subtilus endospores, the spore coat is estimated to contain more than 70 coat proteins, which are organized into an inner and an outer coat layer. The X-ray diffraction pattern of purified B. subtilis endospores indicates the presence of a component with a regular periodic structure, which Kadota and Iijima speculated might be formed from a keratin-like protein. However, after further studies this group concluded that the structure of the spore coat protein was different from keratin. When the B. subtilis genome was sequenced, no ortholog of human keratin was detected. The cortex lies beneath the spore coat and consists of peptidoglycan. The core wall lies beneath the cortex and surrounds the protoplast or core of the endospore. The core contains the spore chromosomal DNA which is encased in chromatin -like proteins known as SASPs (small acid-soluble spore proteins), that protect the spore DNA from UV radiation and heat. The core also contains normal cell structures, such as ribosomes and other enzymes, but is not metabolically active.
What is the function of the cortex?
They also function as a carbon and energy source for the development of a vegetative bacterium during germination. The cortex may osmotically remove water from the interior of the endospore and the dehydration that results is thought to be very important in the endospore's resistance to heat and radiation.
Why are endospores more resistant to PEF?
The reason for the greater resistance of spores to PEF is that the electrical conductivity is considerably less in endospores than in vegetative cells, due to the low water content and relative immobility of ions within the spore core.
How do endospores re-enter vegetative growth?
Endospores re-enter vegetative growth and cell division by a complex process called germination [60]. Germination is triggered by environmental stimuli that are then transduced into a series of interrelated degradation events. This ultimately results in the loss of typical dormant endospore properties [26].
What is endospore germination?
In chemical terms, endospore germination is a process that uses substrates (germinants and endospores) to accumulate a product (the vegetative cell) over time. Since germinants are not consumed, endospore germination can be analysed using mathematical models developed for enzyme kinetics [81–83].
What are endospores in biofilms?
Endospore-forming bacteria present a unique challenge in biofilm studies, as well as to food and beverage manufacturers within processing stages. This chapter discusses the mesophilic endospore formers, such as Bacillus species, with respect to attachment of spores to surfaces and subsequent biofilm development. In addition, many manufacturing processes utilize processing temperatures which are suitable for the growth of thermophilic endospore-forming bacteria, such as Geobacillus and Anoxybacillus strains, increasing concerns of contamination of product. This chapter also highlights the biofilm-forming ability coupled with spore development in these strains. From results obtained to date, biofilm-spore development in themophilic strains seems to be very different from that of mesophilic Bacillus isolates. Future studies will further elucidate the spore-biofilm interaction and allow for better control of such biofilms within industrial settings.
How are endospores formed?
Endospores are formed in response to unfavorable growth conditions in the bacterial environment, most commonly induced by the limitation of nutrients. Sporulation, however, is not the first response of the bacterial cell to nutrient depletion. In fact, nutrient-limited cells initiate several adaptive response mechanisms to reach (chemotaxis), take up (expression of transport systems), or metabolize (induction of catabolic pathways) potential secondary energy sources. Only if these mechanisms fail to provide enough nutrients for continued vegetative growth, the cell commits to the sporulation pathway. Although limitation is critical, a fully starved cell also cannot sporulate, because endospore formation is an energy-demanding biosynthetic process. Cells have to reutilize existing macromolecules, but they also need to synthesize new mRNA and peptides to make structural spore proteins. The process of spore formation is divided into distinct morphological and biochemical stages and has been studied extensively in B. subtilis ( Figure 1 ).
What are endospores made of?
Endospores. Endospores are composed of the DNA-containing core surrounded by a cortex, spore coat and exosporium [84–86], all of which protect the dormant cell from hostile and unfavourable conditions such as desiccation, osmotic shock, extremes of temperature and contact with chemicals such as disinfectants.
What foods are associated with B. cereus endospores?
B. cereus endospores are present in a wide variety of foods, including rice and pasta, milk and dairy products, infant foods, meat products, spices, fresh vegetables, seafood, ready to eat foods, dried foods such as spices, milk powders, and cereal products. Food products such as meat products, soups, vegetables, sauces, and dairy products are often associated with diarrheal food poisoning. Whereas rice and pasta are associated with the emetic type of syndrome.
What is the endospore of bacteria?
Bacterial endospores are simplified forms of the bacteria, consisting of the DNA genome, some small amount of cytoplasm, and a specialized coating that confers resistance to heat, radiation, and other harsh external conditions.
How long do endospores last?
This state may persist for years to decades or even longer.
What disinfectant is used on hysteroscopes?
Some hysteroscopes can be disinfected with glutaraldehyde 2%. This is a chemical germicide that is not corrosive to most hysteroscopes. This disinfectant does not necessarily kill all bacterial endospores, but it is approved by the U.S. Food and Drug Administration (FDA) as effective against all vegetative bacteria, mycobacteria, fungi, and viruses. Instruments must remain submerged for at least 20 minutes in this solution. All lumens must be flushed with this solution to ensure contact and to eliminate air pockets that can prevent contact with the solution. Excellent ventilation is necessary for health care workers to prevent respiratory injury. Glutaraldehyde irritates mucosal membranes including, eyes, nose, and skin. Solution should be kept covered when not in use. Workers must wear protective clothing.
What is the role of akinetes in a cell?
Akinetes are nonmotile cells that differentiate from vegetative cells and serve a perennation role, but in contrast to bacterial endospores are not heat resistant. During akinete differentiation, the cellular structure changes dramatically. The akinetes formed are larger than vegetative cells or heterocysts and, in some strains, can be up to 10-fold larger than vegetative cells. A thickened cell wall and a multilayered extracellular envelope surround the akinetes (Herdman, 1987, 1988 ), but the structure of these layers varies for different species based on their ecological origin ( Fig. 1) ( Braune, 1980; Perez et al., 2016, 2018 ). The akinete shape differs among species from sphere to prolate spheroid. Their size, shape, distribution, and position within a trichome are frequently used as a taxonomic feature ( Komárek, 2010 ). Akinetes contain large amounts of food reserve materials and essential cellular metabolic pools ( Table 1 ).
What is the process of sterilization?
The process is operationally defined as a 12-log reduction of bacterial endospores.27 Not all sterilization processes are alike, however. Steam is the most extensively utilized process and is routinely monitored by the use of biologic indicators (e.g., spore test strips) to show that sterilization has been achieved. When liquid chemical germicides (LCGs) are used to eradicate all microorganisms, they can be called chemical sterilants; however, the US Food and Drug Administration (FDA) and other authorities have stated that these processes do not convey the same level of assurance as other sterilization methods. 28–30 Other commonly used sterilization processes include low-temperature gas such as ethylene oxide (ETO), liquid chemicals, and hydrogen peroxide gas plasma.31
Can high pressure be used for sterile products?
High-pressure processing at around ambient temperature is limited in its inability to destroy bacterial endospores. Because of this limitation, it cannot be used for producing sterile products, and all pressure-treated foods have to be kept refrigerated. However, high pressure can stimulate germination of bacterial spores, which enables the resulting vegetative form to be destroyed. Some variations of the standard single-pressure treatment, such as repeated cycling between high and low pressures, ‘pulsed’ or ‘oscillatory’ pressurization, and combined high pressure and high temperature, enhance the sporicidal effect of high pressure.
What is the efficacy of chemical systems?
The efficacy of many chemical systems is related to the concentration of the active agent, its contact time and the form of delivery. There is invariably a trade-off between antimicrobial activity and ocular toxicity, and comfort and convenience.
Endospore Structure
Endospore Development
- The process of forming an endospore is complex. The model organism used to study endospore formation is Bacillus subtilis. Endospore development requires several hours to complete. Key morphological changes in the process have been used as markers to define stages of development. As a cell begins the process of forming an endospore, it divides asymmetrically (S…
Endospores and Epulopiscium
- Some Epulopiscium-like surgeonfish symbionts form mature endospores at night. These spores possess all of the characteristic protective layers seen in B. subtilis endospores and also contain large amounts of dipicolinic acid. These are the largest endospores described thus far, with the largest being over 4000 times larger than a Bacillus subtilisendospore. The formation of endosp…
Overview
An endospore is a dormant, tough, and non-reproductive structure produced by some bacteria in the phylum Bacillota. The name "endospore" is suggestive of a spore or seed-like form (endo means 'within'), but it is not a true spore(i.e., not an offspring). It is a stripped-down, dormant form to which the bacterium can reduce itself. Endospore formation is usually triggered by a lack of nutrients, a…
Life cycle of bacteria
The bacterial life cycle does not necessarily include sporulation. Adverse environmental conditions usually trigger sporulation, so as to help the survival of the bacterium. Endospores exhibit no signs of life and can thus be described as cryptobiotic. Endospores retain viability indefinitely and they can germinate into vegetative cells under the appropriate conditions. Endospores have survived thousands of years until environmental stimuli trigger germination. T…
Structure
Bacteria produce a single endospore internally. The spore is sometimes surrounded by a thin covering known as the exosporium, which overlies the spore coat. The spore coat, which acts like a sieve that excludes large toxic molecules like lysozyme, is resistant to many toxic molecules and may also contain enzymes that are involved in germination. In Bacillus subtilus endospor…
Location
The position of the endospore differs among bacterial species and is useful in identification. The main types within the cell are terminal, subterminal, and centrally placed endospores. Terminal endospores are seen at the poles of cells, whereas central endospores are more or less in the middle. Subterminal endospores are those between these two extremes, usually seen far enough towards the poles but close enough to the center so as not to be considered either terminal or c…
Formation and destruction
Under conditions of starvation, especially the lack of carbon and nitrogen sources, a single endospore forms within some of the bacteria through a process called sporulation.
When a bacterium detects environmental conditions are becoming unfavourable it may start the process of endosporulation, which takes about eight hours. The
Reactivation
Reactivation of the endospore occurs when conditions are more favourable and involves activation, germination, and outgrowth. Even if an endospore is located in plentiful nutrients, it may fail to germinate unless activation has taken place. This may be triggered by heating the endospore. Germination involves the dormant endospore starting metabolic activity and thus breaking hibernation. It is commonly characterised by rupture or absorption of the spore coat, s…
Importance
As a simplified model for cellular differentiation, the molecular details of endospore formation have been extensively studied, specifically in the model organism Bacillus subtilis. These studies have contributed much to our understanding of the regulation of gene expression, transcription factors, and the sigma factor subunits of RNA polymerase.
Endospores of the bacterium Bacillus anthracis were used in the 2001 anthrax attacks. The powd…
Endospore-forming bacteria
Examples of endospore-forming bacteria include the genera:
• Acetonema
• Actinomyces
• Alkalibacillus
• Ammoniphilus