Obligate Anaerobe

6 Key excerpts on "Obligate Anaerobe"

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  Encyclopedia of Veterinary Science

  • Mukul Anand(Author)
  • 2023(Publication Date)
  • Delve Publishing

    (Publisher)

  O Obligate Aerobe An obligate aerobe is a living organism that needs oxygen to survive. These creatures use oxygen to metabolize compounds such as carbohydrates or fats to obtain energy via cellular respiration. In this type of respiration, oxygen serves as the electron transport chain’s terminal electron acceptor. Aerobic respiration produces more energy (adenosine triphosphate, or ATP) than fermentation or anaerobic respiration, yet obligate aerobes are vulnerable to oxidative stress (Work et al., 2008). Obligate Anaerobe Obligate Anaerobes are microorganisms that are killed by typical oxygen concentrations in the atmosphere (20.95 percent O2). Oxygen tolerance varies amongst species, with some species capable of surviving in conditions with up to 8% oxygen, while others lose viability in environments with more than 0.5 percent oxygen. Owing to a variety of variables, including oxidative stress and enzyme synthesis, Obligate Anaerobes’ oxygen sensitivity has been attributed. Encyclopedia of Veterinary Science 281 Oxygen can also harm Obligate Anaerobes in ways that are not related to oxidative stress. Figure 158: Introduction to Microbiology. Source:https://www.pinterest.com/pin/3870349663683411/ Obligate Parasite An obligate parasite, also known as a holoparasite, is a parasitic creature that cannot complete its life cycle without a suitable host. If an obligate parasite is unable to find a host, it will die. A facultative parasite, on the other hand, can operate as a parasite but does not rely on its host to continue its life cycle. To exploit their hosts, obligate parasites have evolved a variety of parasitic methods. Some hemiparasites and holoparasites are obligate. When it is compatible with the parasite’s nutritional and reproductive needs, it is desirable for the parasite to preserve the host’s health, unless the host’s death is required for transmission.

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  Anaerobic Infections in Humans

  • Sydney Finegold(Author)
  • 2012(Publication Date)
  • Academic Press

    (Publisher)

  For the most part, the anaerobes in which we are interested are part of the indigenous flora of the body, and here may be protected from oxygen in various ways. The presence of aerobic and facultative bacteria facilitates the survival and growth of anaerobes by eliminating peroxides and providing reduced conditions. Even on the surface of the skin and in the mouth, where one would anticipate that anaerobes might have difficulty in growing because of exposure to oxygen, these organisms may survive because of microscopic niches that are quite anaerobic. In laboratory practice, definition of an anaerobe need not be as difficult as suggested by the previous discussion. A practical definition for operational purposes is that an anaerobe is a bacterium that requires a reduced oxygen tension for growth and fails to grow on the surface of solid media in 10% C 0 2 in air (18% oxygen). Facultative organisms are those that can grow both in the presence or absence of air. Strictly speaking, microaerophilic bacteria would be those preferring reduced oxygen tension, such as that provided by 10% CO2 in air, over either aerobic or anaerobic conditions. In actual practice, the term microaero-philic is used commonly for organisms that grow poorly or not at all in air but which grow distinctly better under 10% C 0 2 in air (reduced 0 2 content) or anaerobically. The role of the C 0 2 per se and of the humidity present in jars, as compared to the reduced oxygen tension, has not ordinarily been investigated with these organisms. Aerotolerant organ-isms are anaerobes that tolerate oxygen just enough to grow on the surface of freshly prepared solid media. II. Problems in Classification and Characterization One major problem is that anaerobic bacteria are always found in mixed culture as normal flora and are frequently found in mixed culture in clinical infections. The associations in these mixtures may be so intimate that it becomes extremely difficult to isolate each component of the

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  Veterinary Microbiology

  • D. Scott McVey, Melissa Kennedy, M. M. Chengappa, Rebecca Wilkes, D. Scott McVey, Melissa Kennedy, M. M. Chengappa, Rebecca Wilkes(Authors)
  • 2022(Publication Date)
  • Wiley-Blackwell

    (Publisher)

  33 Gram‐Negative, Non‐Spore‐Forming Anaerobes

  Tiruvoor G. Nagaraja

  Anaerobic bacteria use inorganic or organic molecules – rather than oxygen – as a final electron acceptor to generate energy for metabolism. Anaerobes are broadly categorized as obligate and aerotolerant based on the degree of susceptibility to molecular oxygen. Obligate Anaerobes are adversely affected by oxygen, and the degree of oxygen toxicity varies with species and even strains within a species. When exposed to molecular oxygen, bacteria generate powerful oxidants, such as hydrogen peroxide, superoxide anions, singlet oxygen, and other oxygen radicals. These oxygen radicals interact with cell macromolecules, such as proteins and nucleic acids, to disrupt their structures and cause lethal damage to cells. Obligate Anaerobes lack mechanisms and enzyme systems, such as superoxide dismutase and catalase, to neutralize toxic products. Gram‐negative anaerobes of clinical importance are generally aerotolerant because many of them do contain low levels of superoxide dismutase and catalase or peroxidase and can resist exposure to oxygen, but the duration of tolerance varies with species. Because of aerotolerance, many of the clinical anaerobes can be grown in culture medium that is not pre‐reduced and are able to grow on agar surfaces as long as incubation is carried out under an oxygen‐free atmosphere.

  A number of genera and species of gram‐negative, non‐spore‐forming anaerobes are part of the normal flora of the mucosal lining of the mouth, intestine, and respiratory, urinary, and genital tracts of animals and humans. These organisms are more often opportunistic pathogens and generally cause infections following the breakdown in mucosal or epithelial barriers and the entry of the bacteria into normally sterile sites of the body.

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  ASM Books

  • Randall T. Hayden, Karen C. Carroll, Yi-Wei Tang, Donna M. Wolk, Randall T. Hayden, Karen C. Carroll, Yi-Wei Tang, Donna M. Wolk(Authors)
  • 2016(Publication Date)
  • ASM Press

    (Publisher)

  1

  20 Selected Topics in Anaerobic Bacteriology

  INTRODUCTION

  A diverse community makes up the normal healthy microbiota in humans, and anaerobic bacteria are the primary component (1 –4 ). A wide variety of different environments in the human body support complex microbial communities comprising both obligate and facultative anaerobes (3 , 4 ). At all body sites where anaerobes are part of the indigenous microbiota, Obligate Anaerobes greatly outnumber facultative anaerobes by a factor of 10 up to 1,000 times (Table 1 ) (5 –9 ). Obligate Anaerobes are therefore the predominant type of bacteria present in humans at skin and mucosal surfaces. Microbial-community analysis of healthy human intestinal microbiota also reveals a rich and diverse array of anaerobes including Lactobacillus spp., members of the former Bacteroides fragilis group (i.e., B. fragilis, B. distasonis, B. thetaiotaomicron , B. ovatus , and B. vulgatus ), other Bacteroides species, and Clostridium spp., as well as a wide array of anaerobes that are less clinically encountered (2 , 10 , 11 ). Under normal circumstances, intestinal anaerobes are not pathogenic but are essential for preventing overgrowth of opportunistic organisms or infection with pathogenic bacteria. Colonization resistance against acquisition of enteric pathogens (i.e., Salmonella and Shigella ) and hospital-acquired antibiotic-resistant bacteria (e.g., vancomycin-resistant enterococci and Clostridium difficile ) is provided by the presence of healthy normal bacteria that prevent gastrointestinal colonization by exogenous bacteria (1 , 10 , 12 –18 ).

  Table 1 Diversity of anaerobes in the human bodya, b

  a See references 5 –9 .

  b CFU, colony-forming units; GI, gastrointestinal.

  Recent microbiome studies document clearly that maintenance of the integrity of the intestinal microbiome is essential to health. These microbial communities have important immunomodulatory effects on the development and regulation of host immune function, as well as contributing to the host’s nutrition by providing nutrients and vitamins to cells (1 , 2 , 4 , 11

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  Extremophiles: Diversity, Adaptation and Applications

  • Masrure Alam, Bipransh Kumar Tiwary Tiwary, Masrure Alam, Bipransh Kumar Tiwary Tiwary(Authors)
  • 2008(Publication Date)
  • Bentham Science Publishers

    (Publisher)

  Anaerobes

  Arijit Pal1

  ,

  Sekhar Pal

  2 , *

  1 Department of Microbiology and Biotechnology, JIS University, Agarpara, Kolkata-700109, India

  2 Department of Microbiology, Ramakrishna Mission Vivekananda Centenary College, Rahara, Kolkata-700118, India

  Abstract

  Extremophilicity, or the capability to thrive in environmental conditions considered extreme is generally determined from the human perspective. From that point of view, organisms adapted to scarce, or even the absence of molecular oxygen, can be considered as one of the extremophiles, i.e., anaerobes. In this chapter, various aspects of anaerobic microorganisms are addressed, including their different taxa, their phylogenetic distribution, and the environments from where they have been isolated. Since prokaryotic taxonomy is a dynamic process, here we have emphasized the organisms that are validly placed in taxa and have cultured representatives. In this section, Archaea and Bacteria - the two domains are separately discussed. Similar separation is also maintained while discussing mechanisms of adaptation, as far as possible. Since these two domains share certain properties, the subsequent sections are not separated between these two domains.

  Keywords: Anaerobic microorganisms, Anaerobic bacteria, Anaerobic archaea, ATP synthase, Biogeochemical cycle, Chemoorganotrophs, Extremophiles, Facultative anaerobes, Obligate Anaerobes, Hydrothermal vent, Microaerophiles, Proteobacteria.

  * Corresponding author Sekhar Pal: Department of Microbiology, Ramakrishna Mission Vivekananda Centenary College, Rahara, Kolkata- 700118, India; E-mail: [email protected]

  INTRODUCTION

  “Extremophiles” refer to the organisms that are capable of surviving, or even growing, in extreme environmental conditions, which are otherwise considered as unfavourable to sustain life. There are diverse forms of extremophiles depending on the nature of extreme conditions in which they thrive. For example, acidophiles survive or favour low pH; alkaliphiles survive or favour high pH; halophiles survive or favour high salt concentration; thermophiles survive or favour high temperature; psychrophiles survive or favour low temperature, etc

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  Manual of Environmental Microbiology

  • Cindy H. Nakatsu, Robert V. Miller, Suresh D. Pillai(Authors)
  • 2016(Publication Date)
  • ASM Press

    (Publisher)

  Anaerobic Cultivation TAKASHI NARIHIRO AND YOICHI KAMAGATA 2.1.2

  Anaerobes are key players in global cycles of elements and nutrition in natural and anthropologic ecosystems and are also causative agents of human and veterinary diseases. Numerous studies have sought to develop culturing techniques for anaerobes to enable the elucidation of their basic physiology, pathogenic mechanisms, and ecological functions. This chapter describes a brief history of the development of anaerobic culturing techniques from the historical Hungate technique to techniques and apparatuses commonly used in modern laboratories. In addition, recent progress in anaerobic culturing techniques (e.g., single-cell manipulation and isolation, the six-well plating method, the coculture method, bioreactor-based enrichment, and in situ /in vivo cultivation) are described, with several examples of the application of these techniques for the isolation of anaerobes from natural and artificial ecosystems.

  Anaerobic microorganisms (hereafter designated anaerobes) are key players in global cycles of elements (e.g., carbon, nitrogen, sulfur, and iron) in natural and anthropogenic ecosystems, including aquifer/groundwater (1 ), animal/insect guts (2 , 3 ), rice paddy fields (4 ), rumen (5 ), terrestrial/oceanic subsurfaces (6 , 7 ), wetlands (8 ), biodiesel production processes (9 ), food production processes (10 ), and wastewater treatment processes (11 ). In these anoxic ecosystems, various metabolic groups of anaerobes play roles in specific biochemical reactions, such as fermentation (12 , 13 ), anaerobic ammonium oxidation (anammox) (14 ), sulfate reduction (15 ), iron reduction (16 ), syntrophic substrate oxidation (17 ), and methanogenesis (18 ). In addition to these metabolic groups, anaerobes include human and animal pathogens, which were the main focus in the earliest era of modern microbiology. The challenges of cultivating, characterizing, and controlling these anaerobic pathogens organisms spurred the establishment of modernized microbiology (19 –23

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