The facultative anaerobic bacteria they are bacteria capable of living both in conditions of presence and absence of oxygen. Oxygen is a highly reactive compound and essential for many bacteria and for most living organisms, however, this element is lethal for some species of bacteria.
Among the facultative anaerobic bacteria there are species of industrial and commercial importance, whether in the food, pharmaceutical or cosmetic industries, among others. Other species, on the contrary, are capable of producing lethal diseases for man.
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The main characteristic of facultative anaerobic bacteria is that they can use oxygen in their metabolic processes, but they can also use anaerobic respiration or fermentative metabolism in the absence of oxygen..
Another characteristic, related to the metabolic process, is that facultative bacteria lack the enzyme superoxide dismutase. This enzyme is characteristic of strict aerobic bacteria. The function of the enzyme is the breakdown of superoxide (Otwo-), an intermediate product of aerobic metabolism.
All living beings must obtain energy for their vital processes; This energy is obtained from food, either synthesized by themselves (autotrophs) or previously elaborated and / or processed (heterotrophs).
The energy contained in food is used (partially) for the synthesis of ATP through a series of chemical reactions that are part of metabolism. To do this, they must break chemical bonds within the molecules that make up food..
The breaking of these bonds causes the release of electrons or hydrogen atoms that must be accepted by other compounds. If the final acceptor of the electrons, or hydrogen, is an organic compound, the reaction is known as fermentation, on the other hand, if the final acceptor is an inorganic compound, then we speak of respiration..
During respiration, the most common final electron acceptor is oxygen; it is called aerobic respiration. However, in the absence of oxygen, some organisms, such as some bacteria, may use inorganic compounds other than oxygen as final electron acceptors, anaerobic respiration occurring..
Bacteria can be classified depending on whether or not they use oxygen in their metabolism as follows:
They use oxygen as the final electron acceptor in metabolic processes. This is why they are able to grow and thrive in the presence of oxygen. Finally, strict aerobic species cannot survive in anoxic conditions..
They are a group of bacteria that, despite requiring oxygen, can only thrive in environments where the concentrations of this element are lower (less than 10%) than the normal concentration in the air (20%)..
Species that do not use oxygen in their metabolic reactions. For some anaerobic species, oxygen is a toxic element, being lethal for them, even in very low concentrations. However, some species can tolerate it, and even eventually use it; therefore, anaerobic bacteria can be subdivided into:
They are not capable of using oxygen in their metabolism, but this is not lethal, so they can live in environments with normal oxygen concentrations.
Bacteria that can use oxygen as the final electron acceptor during their energy metabolism, but in the absence of this element they can survive using other metabolic pathways.
Some of the facultative anaerobic bacteria are of great industrial importance. This group includes, for example, the bacteria used to obtain fermented alcoholic beverages, such as wine or beer..
They are also used in the food industry to obtain fermented foods such as cheese, yogurt, among others. Some species are also used to make probiotics.
Among the facultative anaerobic bacteria there are several species capable of causing diseases of different clinical relevance, ranging from self-limited diarrhea to fatal diseases, including many of the nosocomial diseases..
These diseases include, for example, bacterial diarrhea, urinary tract infections, endocarditis, meningitis, peritonitis, pneumonia, and septicemia. Some of these diseases are difficult to treat due to the resistance of bacteria to drugs.
It is a member of the group of Enterobacteriaceae, which can normally be found in the gastrointestinal tract of humans. Among the characteristics of this species are the fact that it is capable of fermenting lactose and degrading tryptophan, but it cannot grow in media with citrate as the sole carbon source..
Although it is part of the intestinal flora, this bacterium is capable of causing diseases in humans, such as diarrhea, urinary tract infections and meningitis..
It is another species of Enterobacteriaceae, like E. coli, but unlike this, it is not capable of fermenting lactose, but it can survive in cultures with citrate as the only carbon source. It can live in the gastrointestinal tract of a great diversity of vertebrate species, including some cold-blooded ones..
This species, together with other species of the genus, are responsible for gastroenteritis.
Bacteria belonging to the group of lactobacillus, of variable forms. It can grow solitary, in pairs or in the form of a chain. The industry uses this species in the production of foods such as yogurt, cheese, sauerkraut, among others..
It is also used as a probiotic, and is generally recognized as safe (GRAS) by the United States Food and Drug Administration (FDA), however, it may be responsible for nosocomial diseases, such as endocarditis.
It is another representative of the group of lactobacilli, as Lactococcus lactis. It is a nonmotile bacillus, incapable of producing spores that can grow singly or in short-chain colonies. It can be facultative anaerobic or microaerobic.
Like L. lactis, It is used in the food industry and as a probiotic. It is also related to nosocomial diseases, including bacteremia, meningitis, and peritonitis.
Small bacillus, not mobile, but above all, it requires blood components for its development. It is one of the main causes of diseases such as ear and respiratory tract infections, meningititis and epiglottitis.
Rod-shaped bacteria that live as a commensal in the digestive tract of humans, as well as other vertebrates. Despite being a traditional member of the intestinal flora of healthy organisms, it can be an opportunistic infectious agent in diseased organisms or when infecting wounds..
Among the diseases associated with this bacterium are firstly diarrhea, urinary tract infections, septicemia, bacteremia, pneumonia, empyema, surgical infections, among others. This bacterium develops resistance to drugs.
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