An obligate aerobe is an organism that requires oxygen to grow. Through cellular respiration, these organisms use oxygen to metabolise substances, like sugars or fats, to obtain energy. In this type of respiration, oxygen serves as the terminal electron acceptor for the electron transport chain. Aerobic respiration has the advantage of yielding more energy than fermentation or anaerobic respiration, but obligate aerobes are subject to high levels of oxidative stress.
An aerobic organism or aerobe is an organism that can survive and grow in an oxygenated environment. In contrast, an anaerobic organism (anaerobe) is any organism that does not require oxygen for growth. Some anaerobes react negatively or even die if oxygen is present. The ability to exhibit aerobic respiration may yield benefits to the aerobic organism, as aerobic respiration yields more energy than anaerobic respiration. In July 2020, marine biologists reported that aerobic microorganisms (mainly), in "quasi-suspended animation", were found in organically-poor sediments, up to 101.5 million years old, 250 feet below the seafloor in the South Pacific Gyre (SPG), and could be the longest-living life forms ever found.
An anaerobic organism or anaerobe is any organism that does not require molecular oxygen for growth. It may react negatively or even die if free oxygen is present. In contrast, an aerobic organism (aerobe) is an organism that requires an oxygenated environment. Anaerobes may be unicellular or multicellular. Most fungi are obligate aerobes, requiring oxygen to survive. However, some species, such as the Chytridiomycota that reside in the rumen of cattle, are obligate anaerobes; for these species, anaerobic respiration is used because oxygen will disrupt their metabolism or kill them. Deep waters of the ocean are a common anoxic environment.
A coccus is any bacterium or archaeon that has a spherical, ovoid, or generally round shape. Bacteria are categorized based on their shapes into three classes: cocci (spherical-shaped), bacillus (rod-shaped) and spirochetes (spiral-shaped) cells. Coccus refers to the shape of the bacteria, and can contain multiple genera, such as staphylococci or streptococci. Cocci can grow in pairs, chains, or clusters, depending on their orientation and attachment during cell division. In contrast to many bacilli-shaped bacteria, most cocci bacteria do not have flagella and are non-motile.
Obligate anaerobes are microorganisms killed by normal atmospheric concentrations of oxygen (20.95% O2). Oxygen tolerance varies between species, with some species capable of surviving in up to 8% oxygen, while others lose viability in environments with an oxygen concentration greater than 0.5%.
Fructooligosaccharides (FOS) also sometimes called oligofructose or oligofructan, are oligosaccharide fructans, used as an alternative sweetener. FOS exhibits sweetness levels between 30 and 50 percent of sugar in commercially prepared syrups. It occurs naturally, and its commercial use emerged in the 1980s in response to consumer demand for healthier and calorie-reduced foods.
The Clostridia are a highly polyphyletic class of Bacillota, including Clostridium and other similar genera. They are distinguished from the Bacilli by lacking aerobic respiration. They are obligate anaerobes and oxygen is toxic to them. Species of the class Clostridia are often but not always Gram-positive and have the ability to form spores. Studies show they are not a monophyletic group, and their relationships are not entirely certain. Currently, most are placed in a single order called Clostridiales, but this is not a natural group and is likely to be redefined in the future.
Coliform bacteria are defined as either motile or non-motile Gram-negative non-spore forming Bacilli that possess β-galactosidase to produce acids and gases under their optimal growth temperature of 35-37°C. They can be aerobes or facultative aerobes, and are a commonly used indicator of low sanitary quality of foods, milk, and water. Coliforms can be found in the aquatic environment, in soil and on vegetation; they are universally present in large numbers in the feces of warm-blooded animals as they are known to inhabit the gastrointestinal system. While coliform bacteria are not normally causes of serious illness, they are easy to culture, and their presence is used to infer that other pathogenic organisms of fecal origin may be present in a sample, or that said sample is not safe to consume. Such pathogens include disease-causing bacteria, viruses, or protozoa and many multicellular parasites.
The Halanaerobiales are an order of bacteria placed within the class Clostridia, and encompassing two families, the Halanaerobiaceae and the Halobacteroidaceae. Originally placed within the highly polyphyletic class Clostridia, according to the NCBI and LPSN, it is now thought to lie outside the Bacillota. Halanaerobiales are halophilic obligate anaerobes with a fermentative or homoacetogenic metabolism.
Bacteroides fragilis is an anaerobic, Gram-negative, pleomorphic to rod-shaped bacterium. It is part of the normal microbiota of the human colon and is generally commensal, but can cause infection if displaced into the bloodstream or surrounding tissue following surgery, disease, or trauma.
Microbial metabolism is the means by which a microbe obtains the energy and nutrients it needs to live and reproduce. Microbes use many different types of metabolic strategies and species can often be differentiated from each other based on metabolic characteristics. The specific metabolic properties of a microbe are the major factors in determining that microbe's ecological niche, and often allow for that microbe to be useful in industrial processes or responsible for biogeochemical cycles.
Food microbiology is the study of the microorganisms that inhabit, create, or contaminate food. This includes the study of microorganisms causing food spoilage; pathogens that may cause disease ; microbes used to produce fermented foods such as cheese, yogurt, bread, beer, and wine; and microbes with other useful roles, such as producing probiotics.
The Pasteur effect describes how available oxygen inhibits ethanol fermentation, driving yeast to switch toward aerobic respiration for increased generation of the energy carrier adenosine triphosphate (ATP).
Klebsiella aerogenes, previously known as Enterobacter aerogenes, is a Gram-negative, oxidase negative, catalase positive, citrate positive, indole negative, rod-shaped bacterium. The bacterium is approximately 1-3 microns in length, and is capable of motility via peritrichous flagella.
Veillonella are Gram-negative bacteria anaerobic cocci, unlike most Bacillota, which are Gram-positive bacteria. This bacterium is well known for its lactate fermenting abilities. It is a normal bacterium in the intestines and oral mucosa of mammals. In humans they have been implicated in cases of osteomyelitis and endocarditis, for example with the species Veillonella parvula.
Fermentative hydrogen production is the fermentative conversion of organic substrates to H2. Hydrogen produced in this manner is often called biohydrogen. The conversion is effected by bacteria and protozoa, which employ enzymes. Fermentative hydrogen production is one of several anaerobic conversions.
Anaerococcus is a genus of bacteria. Its type species is Anaerococcus prevotii. These bacteria are Gram-positive and strictly anaerobic. The genus Anaerococcus was proposed in 2001. Its genome was sequenced in August 2009. The genus Anaerococcus is one of six genera classified within the group GPAC. These six genera are found in the human body as part of the commensal human microbiota.
Ligilactobacillus animalis is a non-motile, homofermentative species in the Gram-positive genus Ligilactobacillus, initially isolated from the dental plaque of primates. L. animalis has optimal growth at 37°C on MRS agar, making this species mesophilic. This species can ferment cellobiose, fructose, glucose, lactose, maltose, melibiose, raffinose, and salicin, but it cannot ferment xylose. The genome size of the type strain is 1.89 Mbp and the G/C content is 41.1%.
Anaerococcus hydrogenalis is a bacterium from the family Peptoniphilaceae. It is present in vaginal discharges and ovarian abscesses. Presence of Anaerococcus hydrogenalis in the gut metabolism and their coline consumption has been associated to cardiovascular diseases. Contrary to most of the species in this genus, Anaerococcus hydrogenalis is indole-positive. Also, some strains in this specie can produce urease.
Anaerococcus tetradius is a bacterium from the family Peptoniphilaceae. It was first isolated from vaginal discharges and ovarian abscesses, but is a common member of the vaginal flora.
