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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.
Biological stabilisation of sludge
Published in Bhola R. Gurjar, Vinay Kumar Tyagi, Sludge Management, 2017
Bhola R. Gurjar, Vinay Kumar Tyagi
The removal of nitrogen in the form of nitrate by conversion to nitrogen gas can be accomplished biologically under anoxic (without oxygen) conditions. The process is known as denitrification. In this process, the facultative anaerobic bacteria obtain energy for growth. from the conversion of nitrate to nitrogen gas, but require an external source of carbon for cell synthesis. Nitrified effluents are usually low in carbonaceous matter and so methanol is commonly used as carbon source, but industrial wastes that are poor in nutrients have also been used. Overall energy reaction of this process may be given as: () 6NO3−+5CH3OH(methanol)→5CO2+3N2+7H2O+6OH−(alkalinity)
Soil Remediation
Published in Kathleen Sellers, Fundamentals of Hazardous Waste Site Remediation, 2018
—Biodegradation can occur aerobically or anaerobically. Aerobic microorganisms use oxygen as the electron acceptor. Anaerobic microorganisms use other electron acceptors such as nitrate, sulfate, iron, manganese, or certain organic compounds. Facultative anaerobic organisms can use oxygen, if it is present, or other electron acceptors if it is not. Most soil bioremediation processes are aerobic. A few are anaerobic or designed to be capable of operating in an anaerobic mode.139,140
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
Arguably, bacteria are the form of life most frequently recovered from MWFs and MWF systems. Commonly recovered bacteria include aerobic and facultative anaerobic genera such as Acinetobacter spp., Alcaligenes spp., Bacillus spp., Blastomonas spp., Citrobacter spp., Comamonas spp., Empedobacter spp., Micrococcus spp., Morganella spp., Mycobacterium spp., Pseudomonas spp., Shewanella spp., Sphingomonas spp., and Wautersiella spp. (31–34). Pseudomonas spp. is the most frequently recovered genus in MWFs and is characterized as gram-negative, facultative anaerobic Gammaproteobacteria, occurring ubiquitously in environmental sources such as soil and water. As noted above, bacterial taxonomic classification is in flux, and numerous current genera (for example, Acinetobacter, Citrobacter, and Comamonas) were historically all members of the genus Pseudomonas. Consequently, although recent papers reporting MWF taxonomic profiles appear to indicate that the common taxa recovered from MWFs have changed since the 1960s and 1970s, in reality, most of the change reflects differences in taxonomic classification rather than actual differences in bacterial populations. Additionally, genomic profiling has identified microbes not previously detected due to the limitations of historical culture test methods.
The perinatal period, the developing intestinal microbiome and inflammatory bowel diseases: What links early life events with later life disease?
Published in Journal of the Royal Society of New Zealand, 2020
Fathalla Ali, Kei Lui, Alex Wang, Andrew S. Day, Steven T. Leach
As previously described, Bifidobacterium in caesarean-delivered infants is either absent or present at low levels following birth, with levels remaining lower, compared to vaginally delivered infants, until 3–4 months of age (Chua et al. 2017). Therefore in caesarean-delivered infants, Bifidobacterium is generally not the dominant bacteria amongst the early colonisers. Under these conditions the early colonisers will be dominated by facultative anaerobic bacteria in contrast to strict anaerobes of the vaginally delivered infants (Arboleya et al. 2012). This increase in facultative anaerobic bacteria increase the growth of pathogenic and potential pathogenic bacteria and contribute to decreased bacterial diversity (Arboleya et al. 2012). Therefore, caesarean-delivered infants will have a reduced benefit from breastfeeding in the developmentally sensitive window immediately after birth. Considering this, the evidence that breastfeeding protects against later morbidities (Yan et al. 2014; Lodge et al. 2015; Bentley et al. 2016) may not be due to breastfeeding alone, but may be due in part, to the combined beneficial activity of Bifidobacterium and HMO.