China
Africa
Explore chapters and articles related to this topic
Microbial Ecology
Published in Volodymyr Ivanov, Environmental Microbiology for Engineers, 2020
The following groups of microorganisms differ in their relation to oxygen: Obligate anaerobic prokaryotes produce energy by fermentation (it is an intramolecular oxidation–reduction without an external acceptor of electrons) or by anoxic respiration (electron acceptors are not oxygen); they can die after contact with oxygen because they have no protection against such the toxic products of oxygen reduction such as hydrogen peroxide (H2O2), superoxide radical (O2−), and hydroxyl radical (OH●).Tolerant anaerobes produce energy by fermentation or by anoxic respiration but can survive after contact with oxygen due to a protective mechanism against oxygen radicals.Facultative anaerobic bacteria are capable of producing energy either anaerobically if oxygen is absent or by aerobic respiration if oxygen is present.Microaerophilic bacteria prefer low concentrations of dissolved oxygen in the medium.Obligate aerobes produce energy by aerobic respiration only.
Microbial Biotechnology
Published in Firdos Alam Khan, Biotechnology Fundamentals, 2020
Although aerobic organisms use oxygen as a terminal electron acceptor during respiration, anaerobic organisms use other electron acceptors. These inorganic compounds have a lower reduction potential than oxygen, which means respiration is less efficient in these organisms and leads to slower growth rates than those of aerobes. Many facultative anaerobes can use either oxygen or alternative terminal electron acceptors for respiration, depending on the environmental conditions. Most respiring anaerobes are heterotrophs, although some do live autotrophically. All the processes described following are dissimilative, which means that they are used during energy production and not to provide nutrients for the cell (assimilative). Assimilative pathways for many forms of anaerobic respiration are also known.
Microbial biotechnology
Published in Firdos Alam Khan, Biotechnology Fundamentals, 2018
While aerobic organisms use oxygen as a terminal electron acceptor during respiration, anaerobic organisms use other electron acceptors. These inorganic compounds have a lower reduction potential than oxygen, which means respiration is less efficient in these organisms and leads to slower growth rates than aerobes. Many facultative anaerobes can use either oxygen or alternative terminal electron acceptors for respiration, depending on the environmental conditions. Most respiring anaerobes are heterotrophs, although some do live autotrophically. All of the processes described in the following text are dissimilative, which means that they are used during energy production and not to provide nutrients for the cell (assimilative). Assimilative pathways for many forms of anaerobic respiration are also known.
Organic mass and nitrogen removal kinetic modeling in sequencing batch reactor
Published in Journal of Applied Water Engineering and Research, 2023
Estefanía Freytez, Adriana Márquez, María Pire, Edilberto Guevara, Sergio Pérez
In an aqueous medium in the absence of molecular oxygen such as the anaerobic and anoxic phases associated with SBR, some oxidized inorganic compounds (e.g. NO3- (Denitrification), NO2- (Denitrification), SO4−2 (Sulfate reduction), Carbon Dioxide (Methanogenesis) PO4−3 among others) could act as electron acceptors for certain anaerobic organisms of the facultative type. According to Metcalf & Eddy, the organisms that generate energy by fermentation and that can grow, both in the presence and the absence of molecular oxygen, are called facultative anaerobic organisms, and can be classified into two groups, according to their metabolic possibilities. Pure facultative anaerobic organisms can change from fermentative to respiratory metabolism, depending on the presence or absence of molecular oxygen. Aerotolerant anaerobic organisms have a strictly fermentative metabolism, but are relatively insensitive to the presence of molecular oxygen.
Microbiology in Water-Miscible Metalworking Fluids
Published in Tribology Transactions, 2020
Frederick J. Passman, Peter Küenzi
Although no individual bacterial or archaeal species can thrive in all environments overall, these two branches of life exhibit temperature tolerance and metabolic ranges that substantially exceed both the environmental tolerance and metabolic diversity scope of all other organisms. As a domain, bacteria are present in most habitats on Earth, in the atmosphere, and in space (27–29). Some species (aerobes) require oxygen; others (anaerobes) can only thrive when oxygen is absent. Facultative anaerobes—bacteria that behave like aerobes when sufficient oxygen is present and like anaerobes when the amount of oxygen present is not sufficient to support aerobic metabolism—are especially important biodeterioration agents. Particularly within biofilm communities, they scavenge oxygen, creating conditions suitable for obligate anaerobes. Some bacterial species use carbon dioxide as their sole source of carbon, whereas others require organic carbon as food. Bacteria thrive in temperatures low or high (−5 °C to well over 100 °C), classically divided into psychrophiles (<20 °C), mesophiles (20–40 °C), thermophiles (40–60 °C), and extreme thermophiles (>60 °C). Bacteria may withstand various concentrations of pollutants and salts and feel right at acidic, neutral, or alkaline pH ranges (30).
Aerobic and anaerobic enrichment cultures highlight the pivotal role of facultative anaerobes in soil hydrocarbon degradation
Published in Journal of Environmental Science and Health, Part A, 2019
Errol D. Cason, Jan-G Vermeulen, Walter J. Müller, Esta van Heerden, Angel Valverde
In both the Star Diamonds and the Free State Groundworks enrichments, Pseudomonas spp. were identified both in anaerobic and aerobic conditions. Pseudomonas have presented with high potential for hydrocarbon degradation. This is due to their metabolic diversity, high resistance to chemical agents such as hydrocarbons and their abundance in microbial communities.[53] In the Free State Groundworks enrichments, both Pseudomonas spp. and Citrobacter spp. were present under aerobic and anaerobic conditions at 25 °C. The Free State Groundworks enrichment also consists of various other Enterobacteriaceae, further showing the importance of facultative anaerobic bacteria for hydrocarbon degradation in these environments. Shifts in environmental conditions will result in frequent changes in biological, chemical and physical components of soil ecosystems. Facultative anaerobic bacteria have the ability to adapt to these changing conditions since they can utilize fermentation or anaerobic respiration, for example nitrate reduction, for growth under oxygen deprived conditions. This is in contrast to obligate aerobes and anaerobes, which will either perish or switch to an oligotrophic lifestyle coupled with an absence of growth.[54]