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Reproduction, Proliferation, and Growth
Published in Volodymyr Ivanov, Environmental Microbiology for Engineers, 2020
Cell differentiation is the transformation of microbial cells into specialized cells. Examples of such cells are as follows: An endospore is an anabiotic (i.e., temporarily not active) cell with low water content, covered by a thick envelope, serving for survival under unfavorable conditions for growth, e.g. starvation, dry environment, or high temperature.An exospore is similar to an endospore in its properties but it is not formed in the mother cell; the main functions of these cells are to increase survival and dispersion of cells in the environment.An anabiotic cyst is an enlarged cell whose main function is to increase the cell survival rate.Nitrogen-fixing cysts and bacteroides are enlarged cells whose main function is the transformation of atmospheric nitrogen into amino groups of organic substances.
Foodborne Illness
Published in Gary S. Moore, Kathleen A. Bell, Living with the Earth, 2018
Gary S. Moore, Kathleen A. Bell
Another important characteristic useful in identifying bacteria is the ability to grow in the presence or absence of oxygen. Aerobic bacteria require oxygen for growth, while the growth of anaerobes such as Clostridium is inhibited by the presence of oxygen (Figure 8.12). Some organisms, such as Campylobacter, are microaerophiles, which require low concentrations of oxygen for growth. If the anaerobe Clostridium botulinum is suspected, the investigator might search for endospores, which are structures produced during the life cycle of certain bacteria (Figure 8.13). Endospores can withstand extreme heat, harsh chemicals, and are very difficult to destroy. The dehydrated spore consists of bacterial DNA, a little RNA, some enzymes, and several layers around the spore including a thick protein spore coat that confers resistance to harsh chemicals. The spore cytoplasm also contains dipicolinic acid that forms a complex with calcium. The dipicolinic acid is a major factor in the heat resistance of spores and is essential for later resuming metabolic functions. Aside from the characteristics mentioned earlier, several other factors such as motility, lactose fermentation, or growth on a specific medium are properties that aid in the identification of bacteria.
Biological Fundamentals
Published in Roger T. Haug, of Compost Engineering, 2018
Some bacteria are capable of producing dormant forms of the cell, which are more resistant to heat, radiation, and chemical disinfection. An endospore is a thick-walled, relatively dehydrated unit formed within a bacterium and released upon cell lysis. Cysts and microcysts are formed from an entire cell that develops a thickened cell wall. Mycelial bacteria can produce spores (exospores) that can survive prolonged periods. Of the three types of dormant forms, endospores are generally more stable under adverse conditions that cysts or exospores. These forms of bacteria become significant when requirements for heat inactivation are considered (Chapter 5).
Human and livestock pathogens and their control during composting
Published in Critical Reviews in Environmental Science and Technology, 2022
Endospores can be inactivated by two mechanisms: damage to the DNA due to dry heat or to spore proteins due to wet heat (Setlow, 2014), meaning that spores formed at mesophilic temperature could be inactivated during the thermophilic phase. Temperatures at which sporulation occurs influence the spore resistance to wet heat and biocides (Harvey, 2019). Spores formed at lower temperature are more sensitive to acids and wet heat than spores produced at temperatures closer to their optimum growth temperatures. This was reported for both anaerobic (Malleck et al., 2018) and aerobic spore-forming bacteria (Melly et al., 2002). However, this trend can be inconsistent among different strains within the same species (Harvey, 2019). B. anthracis spores generated at 45 °C are more resistant to wet heat than those sporulated at 25 °C (Baweja et al., 2008). Nevertheless, the resistance of B. anthracis spores does not increase for spores sporulated at temperatures higher than 37 °C (Harvey, 2019), suggesting that sporulation should occur at a maximum temperature of 37 °C for minimal survival.
Microbiology in Water-Miscible Metalworking Fluids
Published in Tribology Transactions, 2020
Frederick J. Passman, Peter Küenzi
In the microbial world, dormancy is also well known: spore-forming bacteria produce endospores under stressful environmental conditions such as lack of nutrients. Endospores are tough, desiccated, nonreproductive structures that help these bacteria to survive for perhaps millions of years (81). Fungi also produce spores as part of their reproduction that—like plant seeds—are able to persist for a long time without germinating. The common term spore for both fungal spores and bacterial endospores can be confusing. The structure and chemical composition of fungal spores are quite different from those of bacterial endospores.
Sustainable repairing and improvement of concrete properties using artificial bacterial consortium
Published in Journal of Sustainable Cement-Based Materials, 2022
Hala H. A. Mahmoud, Mohamed H. Kalaba, Gamal M. E. El-Sherbiny, Abdelzaher E. A. Mostafa, Mohamed E. A. Ouf, Waleed M. F. Tawhed
Strength improvement of cement-based materials by the addition of bacterial cells has been reported over the recent decade and has been mainly due to bacterial-induced calcite precipitation. However, the ability of bacteria to survive, grow and keep their metabolic activity in concrete is doubtful. This research highlights the ability of bacterial consortium to heal small cracks of concrete and improve its properties. For this reason, we isolated six bacterial isolates from extreme environments which were primarily characterized as spore-forming Gram-positive bacilli. Endospores of bacteria are a special resistant dormant stage with strong cell walls that are capable of surviving in harsh conditions for a long time [28]. The development of endospores makes the bacteria able to resist extreme environmental, mechanical and chemical stress through the mixing of concrete [29]. Therefore, the bacterial spores, in addition to the required nutrients, are introduced to the concrete during the mixing process. Consequently, bacteria will stay in the concrete in the form of spores until a crack forms. When the cracks occur in concrete and water enters these cracks, it dissolves the nutrients and activates the spores to germinate into vegetative bacterial cells. The bacteria then fill the cracks by forming calcium carbonate. When these precipitations cover the cracks and the entrance of water and air are blocked, in this situation, the bacteria return to their “dormant mode” (sleep) [30, 31]. Our study showed the ability of bacterial isolates MK and NW-9 to survive and grow in extreme conditions which include the growth at pH 12 and temperature ranging from 20 to 60 °C. The bacterial isolates which can grow perfectly at pH values above 9, often at pH 10-13, are called alkaliphiles [32]. Alkaliphilic bacteria like Bacillus species can live in concrete with its extreme conditions; consequently, they are the highly targeted genus of bacteria for bio self-healing concrete technology [4]. The previous report noted that the pH of fresh concrete is usually between 10 to 13 and its temperature can go up to 70°C, especially during the mixing step [33]. It is of great importance that the bacteria employed to make self-healing concrete have certain characteristics such as the ability to oxidize organic acids and/or produce urease enzyme [34]. Therefore, the bacterial isolates were tested for urease production. Three bacterial isolates MK, NW-9 and NW-1 produce urease enzyme which breaks down urea, producing both ammonia and carbonate. The produced ammonia increases the pH of the environment and carbonate binding with calcium ions found in the environment causing the development of CaCO3 precipitates according to the following equations [12, 35–37]: