Biological Sciences
Bacterial Endospores
Bacterial endospores are dormant, highly resistant structures formed by certain species of bacteria as a survival mechanism in response to harsh environmental conditions. They are composed of a tough, protective coat that shields the bacterial DNA and other essential molecules. Endospores can remain viable for long periods and are notoriously difficult to eradicate, making them a significant concern in various industries and healthcare settings.
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10 Key excerpts on "Bacterial Endospores"
eBook - PDF- C. H. Werkman, P. W. Wilson, C. H. Werkman, P. W. Wilson(Authors)
- 2013(Publication Date)
- Academic Press(Publisher)
The exist- ence of a fourth type, the gonidium, is claimed by certain bacteriologists. A. THE ENDOSPORE The endospore is an intracellular spore formed chiefly by certain bacteria and capable of reaching a high degree of resistance. Endospore formation is more prevalent among the rod-like bacteria and is the basis for the anaerobic genus Clostridium and the facultative Bacillus. How- ever, it is found, although rarely, in other groups. We thus have the endospore-f orming Planosarcina ureae, Spirillum amylijerum, and Vibrio desulfuricans. The importance of endospore formation is twofold : first, it constitutes the only certain and reproducible cyclostage in bacteria; second, the high resistance which it may attain has determined the bacteriological methods of sterilization. The practical importance of these methods in medicine and in the food industries cannot be overestimated. The endospore appears as a highly refractive body inside a mother cell usually called a sporangium (Fig. 2.13). A mature spore is difficult to stain because of the low permeability of its coat; however, when the permeability of the coat is increased by the application of heat, the spore content stains deeply with basic dyes and, once stained, is not readily decolorized. The spore becomes somewhat flattened when dried on a solid surface such as the surface of the collodion film used to mount bacteria for observation with the electron microscope, and the content of the normal spore is highly opaque to electrons at 50 or 60 kv. 1. Structure and Chemical Composition of the Endospore The endospore consists of a dense cytoplasm usually containing one to several nuclei and surrounded by a cytoplasmic membrane. In 52 GEORGES KNAYSI certain species, the cytoplasmic membrane is surrounded by two coats as in strain C2 of Bacillus mycoides (Knaysi, Baker, and Hillier, 1947) ; in other species there is only one coat, as in Bacillus megatherium (Knaysi and Hillier, 1949).
eBook - PDF- Arthur T. Johnson(Author)
- 2018(Publication Date)
- CRC Press(Publisher)
464 Biology for Engineers of protein ( Figure 6.15.3 ). This coat makes the endospore resistant to many harsh chemi-cals (Tortora et al., 2001). Most of the water present in the endospore is eliminated, and endospores do not carry out metabolic reactions. Endospores can remain dormant for thousands of years. This durability and the fact that some very virulent bacteria produce endospores is the reason that they are so dangerous. They are resistant to processes that normally kill vegetative cells. The germination of the endospore into its vegetative form is triggered by physical or chemical damage to the protein coat. Enclosed enzymes then break down the layers sur-rounding the endospore. Water enters, and metabolism resumes. Sporulation is not a reproductive process. One vegetative cell forms one spore, and one spore forms one vegetative cell. There is an extremely small chance that any given spore will return to its vegetative state. Two genera of bacteria form endospores. The first is the genus Clostridium , an obligate anaerobe. C. tetani causes the disease tetanus; C. botulinum causes botulism; C. perfringens causes gas gangrene and foodborne diarrhea. The second genus is Bacillus , which includes B. anthracis , causing anthrax, B. thuringiensis , a bacterial pathogen, and B. cereus , which can cause a form of food poisoning (Tortora et al., 2001). Processing food to ensure safety requires the reduction of viable endospores to a negli-gible level. Because it is impossible to ensure that all spores are completely eliminated, a standard reduction rate of 10 − 12 has been accepted. That means that one surviving endo-spore for each 10 12 cans processed is acceptable. Through a combination of temperature and time, thermal processes for food sterilization can be designed (Teixeira, 1992; Johnson, 1999). Similar considerations are important for the sterilization of medical devices and bioreactor growth media.
eBook - PDF- Cyril Ponnamperuma(Author)
- 2013(Publication Date)
- Academic Press(Publisher)
The developmental events are very similar in all bacteria that form endospores. There-fore, endospores should be considered part of a highly evolved developmental cycle and are not so likely to be found in primi-tive biological communities as organisms with less complex life cycles. If an organism survived a voyage to another planet the probability of detecting the microbe by a future probe will 109 RICHARDS. HANSON depend on the microbes ability to survive on the planet and on its ability to to propogate in the new environment. In con-sidering the information concerning the giant planets that we now have, compounds known to be energy sources for procaryotes and that are potentially available in those parts of the atmos-phere with liquid water, are reduced nitrogen compounds, methane, small molecular weight hydrocarbons, and radiant energy. This assumes that other nutrients including a nitrogen source, phosphate, sulfur, and appropriate carbon source, and many micronutrients required for metabolism are also present. A discussion of the recent discoveries of resting stages in organisms capable of using some of these energy sources is therefore relevant. II. DORMANCY AND LONGEVITY OF Bacterial Endospores It is not the function of this chapter to provide a comp-rehensive and detailed description of the structure and prop-erties of resting cells. I have attempted to write this con-tribution for the scientists who are not biologists by profes-sion and to provide an overview of the types and properties of resting cells as well as references to more detailed informa-tion. The term resting cells is meant to include cells that are morphologically distinct from growing or vegetative cells, that do not divide until a morphogenesis to the vegetative state occurs, that have reduced metabolic rates and are gener-ally more resistant to environmental changes than growing cells. The term dormancy is generally applied to describe resting stages.
eBook - PDF- Jim McLauchlin, Christine Little, Betty C. Hobbs(Authors)
- 2007(Publication Date)
- CRC Press(Publisher)
Endospores are extremely robust and can survive extremes of physical conditions such as chemical disinfection and heat treatment, although there is some variation in resistance between bacterial species. Endospores can survive in dormant conditions for very long periods under adverse conditions, however when these conditions become more favourable, the spores germinate to produce vege- tative cells (see Figure 2.6). Although the sensitivity of endospores to physical factors varies, some spores can withstand high temperatures for long periods. The processes for the sterilization of canned foods are based on the time and temperature that is required to destroy the most heat-resistant spores. Bacterial spores, when allowed to multiply in food- stuffs, may be responsible for spoilage (including the production of gas) as well as production of toxins that cause disease. Further information on conditions necessary to kill micro-organisms can be found in Chapter 3. PARASITES, ALGAE AND FUNGI An understanding of eukaryotic organisms is important in food poisoning and food hygiene since raw foods can harbour viable helminths, nematodes and protozoa that cause infections. In addition food acts as a vehicle for toxins from algae and fungi, and fungi are also of importance as a cause of food spoilage. Parasites, algae and fungi 27 Helminths and nematodes (the flatworms and roundworms respectively) are a group of eukaryotic animal parasites that are also infectious to humans. The most important flatworms are the liver fluke (Fasciola hepatica) and the tapeworms of the genus Taenia. Both flatworms and tapeworms are multi- cellular organisms that have complex lifecycles involving more than one host. As these infections are more common in developing countries, these are further discussed in Chapter 18. Liver flukes develop as ‘leaf-like’ animals in the bile ducts of humans, sheep and cattle (the definitive host) and are about 2.5 cm long by 1 cm wide.
eBook - PDF- J.-M. Ghuysen, R. Hakenbeck(Authors)
- 1994(Publication Date)
- Elsevier Science(Publisher)
J -M Ghuysen and R Hakenbeck (Eds ), Hu~krrol ('ell Wall 8 1994 Elsevier Science B V All rights reserved 167 CHAPTER 8 Cell wall changes during bacterial endospore formation C.E. BUCHANANI, A.O. HENRIQUES2 and P.J. PIGGOT3 'Department of Biological Sciences, Southern Methodist University, Dallas, TX 75275 0376, USA, 2Cenbo de Tecnologra Quimica e Bioldgica, Apartado 127, 2780 Oeiras, Portugal and 'Department of Microbiology and Immunology, Temple University School of Medicine, Philadelphia, PA 19140, USA 1. Description of sporulation 1.1. Overview Bacterial endospore formation is a primitive cellular differentiation that is induced by nu- trient depletion. An early stage is an asymmetrically located division which yields two distinct cells that have radically different developmental fates. The smaller cell (the pre- spore) is engulfed by the larger cell (the mother cell) and develops into the mature spore; the mother cell ultimately lyses. The mature spore is characterized by its resistance to a variety of environmental stresses. There are several periods when wall metabolism during the developmental cycle is substantially different from vegetative wall metabolism; some of these involve new wall synthesis whereas others are degradative. 1.2. Stages of sporulation Early microscopy studies enabled investigators to identify a series of intermediates in the morphological transition from vegetative cell to spore; these stages are now convention- ally designated with Roman numerals [l] (Fig. I), with the vegetative bacterium desig- nated stage 0 (zero). The overall process is very similar for all species of Bacillaceae that have been studied [2]. Soon after the start of sporulation, the nucleoid rearranges to form an axial filament (stage I); the significance of this rearrangement remains unclear. Formation of the asymmetrically located spore septum is defined as stage I1 of sporula- tion.
eBook - PDFCell Surface Engineering
Fabrication of Functional Nanoshells
- Rawil Fakhrullin, Insung Choi, Yuri Lvov(Authors)
- 2014(Publication Date)
- Royal Society of Chemistry(Publisher)
Secondly, a repair system is activated at the molecular level that restores DNA or proteins damaged by external stressors. Thirdly, the reduced permeability of the spore presents a barrier to fatal chemicals and enzymes, thus reducing the possibility of threats to crucial molecules in the spore core, such as enzymes or DNA. Although multiple factors are involved in the protective mechanisms of spores, the formation of the spore shell is probably the most dramatic event of sporulation (Figure 8.1b). The peptidoglycan layers of the cortex play a crucial role in preventing dehydration of the core. Over the cortex is the coat, which adds resistance to chemical and enzymatic threats. Without the coat, the cortex is vulnerable to peptidoglycan-degrading lysozymes. The exo-sporium is the outermost layer of the shell, which comes into contact with the environment and contains several enzymes involved in germination. Figure 8.1 (a) Tardigrades in active state and in the anhydrobiotic state. (b) The structure of bacterial endospore. Artificial Spores 143 Thus, the shells of spores have a hierarchy of layers, and each stratum has an orthogonal function. Dormant endospores sense the condition of the external environments, and when circumstances become favorable for growth, the spores are con-verted back into growing cells through the process called germination. 9 Germination is usually initiated by the presence of nutrients that bind to receptors in the spore’s inner membrane. Although the precise mechanism has not been known so far, the following events take place: (1) release of small molecules including ions (H 1 , Zn 2 1 , and Ca 2 1 ) and dipicolinic acid from the spore core; (2) hydrolysis of the peptidoglycan cortex; (3) water uptake and expansion of the shrunk spore core. Sporulation represents an intelligent strategy that protects cells tem-porarily from nutritionally unfavorable local conditions using dormancy.
eBook - PDF- Michele S. Swanson, Elizabeth A. Joyce, Rachel E. A. Horak(Authors)
- 2022(Publication Date)
- ASM Press(Publisher)
It would take a whole book to describe what is known about this fascinating biology, and even then we would be covering only a fraction of the inner workings of such complex differentiation processes. Certainly this elaborate system of differentiation will challenge microbiologists for some time. CASE REVISITED: Toughening up the microbial way Is it possible for ancient bacterial spores to remain viable after millions of years in the abdominal tissues of fossil bees preserved in amber? The experiment described in the case study certainly suggests so. But was their turbid culture sufficient proof that the bright, microscopic structures were indeed endospores that had germinated and grew into Bacillus cells? Many scientists are skeptical, arguing that it is unlikely that spores could remain viable after such a long time. Absolute confirmation for this report would be hard to come by. More conclu- sive evidence could be produced by PCR-amplifying specific genes, such as 16S rRNA, from DNA extracted from the spores and matching it to the 16S rRNA sequence obtained from the grown Bacillus cultures. But recovering intact DNA directly from spores is difficult because harsh procedures such as mechanical shearing with glass beads are needed to break their tough coat and cortex and release their DNA, procedures that would degrade the DNA. It has been reported that small (microscale) chambers can be used to deposit spores within a drop of liquid where they can be superheated to release DNA of PCR quality. However, these approaches have not yet made it into mainstream laboratories. Hence, conclusive evidence is still not readily available. However, if the amber protected the abdominal tissues of the fossilized bees, which are considerably more sensitive to environmental stressors and the passage of time than bacterial spores, it is plausible that the spores remained viable throughout this time.
eBook - PDFAn Introduction to Microbiology
Pharmaceutical Monographs
- W. B. Hugo, J. B. Stenlake(Authors)
- 2014(Publication Date)
- Butterworth-Heinemann(Publisher)
In addition an interesting correlation has been shown to exist between heat resistance of spores and their dipico-linic acid and Ca ++ content; heat resistance is associated with a high content of dipicolinic acid and calcium ions. It has also been 21 AN INTRODUCTION TO MICROBIOLOGY suggested that the heat resistance of the spores lies in a special structural form assumed by spore protein during sporulation in which the protein molecules are cross-linked by calcium dipico-linate molecules to produce a heat-resisting structure. Analyses of spores have shown that they have a higher cystine content than the corresponding vegetative form. Although some workers have sought to show that there is a significant correlation between cystine content and the radiation resistance of spores, this has also been disputed. Much work has been carried out to resolve these theories but the spore nevertheless remains a resistant form of a micro-organism and eventually the full story of the resistance of the bacterial spore is emerging and appears not to be general for all spore-forming species. The change from spore to vegetative form occurs in two stages, the first called germination and the second called outgrowth. (The term germination is often applied to the entire process.) During germination (the first stage) there is a loss of refractivity, an increase in ease of staining with simple stain procedures, and a loss of heat resistance together with a decrease in dry weight. Out-growth is accompanied by increase in size of the spore, the splitting of the spore coat and emergence of the vegetative form, which may then if the external conditions are favourable begin to divide. The spore coat may split, equatorially or near the pole of the cell; this process is often characteristic of a given bacterial species.
eBook - PDFBioluminescent Microbial Biosensors
Design, Construction, and Implementation
- Gerald Thouand, Robert S. Marks, Gerald Thouand, Robert S. Marks(Authors)
- 2016(Publication Date)
- Jenny Stanford Publishing(Publisher)
Overall, these layers protect the valuable DNA inside the spore from environmental damage due to UV light, extreme temperatures, irradiation, toxic compounds, extreme humidity levels, and other harmful factors. Additionally, the spores of some Bacillus species have a further protective outer layer composed of proteins, lipids, and carbohydrates, called an exosporium. In bacterial species that are human or animal pathogens, this layer protects their spores from the host immune response. Germination of the spore occurs when receptors on the spore surface sense nutrients in the surrounding environment. These germination receptors respond to specific nutrients and trigger the onset of germination. Bacillus subtilis spores have been found to germinate in the presence of L-alanine, L-valine, or a combination of L-asparagine, D-glucose, D-fructose, and K + [11]. The detailed knowledge of the spore at the functional, structural, and molecular levels, as well as the robustness of spores, makes them ideal candidates for use as vehicles for whole-cell biosensing systems and as platforms for display of recombinant heterologous proteins for applications in bioanalysis. 10.2 Whole-Cell Biosensors Inducible bacterial whole-cell biosensors are comprised of genet-ically engineered bacterial cells harboring a plasmid that bears a reporter element under the control of a specific operator/promoter (O/P). It is necessary to also have a regulatory/recognition element coding for a protein that will bind to an analyte of interest and, thus, either bind to (positive regulation) or release (negative regulation) the O/P region to begin transcription of the reporter element. Within a certain concentration range, this interaction results in an analyte dose-dependent response that is detectable by a color change, light emission, or other quantifiable signal, depending on the nature of the reporter and detection method employed (Fig. 10.2).
eBook - PDF- A.N. Barker(Author)
- 2012(Publication Date)
- Academic Press(Publisher)
Research support was provided by the United States Army Research Office^ Grant No. 4-75-G-0U2. REFERENCES Alderton, G. and Snell, N. (1963). Base exchange and heat re-sistance in bacterial spores. Biochemical and Biophysical Research Communications à JjO, 139. Alderton, G. and Snell, N. (1969). Chemical states of bacterial spores: Dry heat resistance. Applied Microbiology Λ 17, 745. Chung, L., Rajan, K.S., Merdinger, E. and Grecz, N. (1971). Co-ordinative binding of divalent cations with ligands related to bacterial spores: Equilibrium studies. Biophysical Jour-nal j 2i, 469. Church, B.D. and Halvorson, H. (1959). Dependence of heat re-sistance of Bacterial Endospores on their dipicolinic acid content. Nature 3 (London). 183, 124. Fleming, H.P. (1962). Ph.D. Dissertation, University of Illinois. Grecz, N., Smith, R.F. and Hoffmann, C.C. (1970). Sorption of water by spores, heat killed spores, and vegetative cells. Canadian Journal of Microbiology 9 J^ö, 573. Leanz, G. and Gilvarg, C. (1973). Dipicolinic acid location in intact spores of Bacillus megaterium. Journal of Bacteriology Λ 114, 455. Lechowich, R.U. and Ordal, Z.J. (1962). The influence of the sporulation temperature on the heat resistance and chemical composition. Canadian Journal of Microbiology^ J3, 287. Maeda, Y., Fujita, T., Sugiura, Y. and Koga, S. (1968). Physi-cal properties of water in spores of Bacillus megaterium. Journal of General and Applied Microbiology , (Tokyo). 2i, 217. Calcium Chelation and Heat Resistance 543 Perry, J.J. and Foster, J.W. (1955). Studies on the biosynthesis of dipicolinic acid in spores of Bacillus cereus var. mycoides· Journal of Bacteriology, 6£, 337. Rieman, H. (1963). Germination of bacterial spores with chela-tors. Ph.D. Thesis, Copenhagen. Tang, T., Rajan, K.S. and Grecz, N. (1968). Mixed chelates of Ca(II)-pyridine-2,6-dicarboxylate with some amino acids re-lated to bacterial spores. Bio-physical Journal, £, 1458. Tang, T., Rajan, K.S.
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