Citrobacter freundii is a species of facultative anaerobic gram-negative bacteria of the family Enterobacteriaceae.The bacteria have a long rod shape with a typical length of 1–5 μm. Most C. freundii cells generally have several flagella used for locomotion, but some do not and are non-motile. C. freundii is a soil organism, but can also be found in water, sewage, food and in the intestinal tracts of animals and humans. The genus Citrobacter was discovered in 1932 by Werkman and Gillen. Cultures of C. freundii were isolated and identified in the same year from soil extracts.
A facultative anaerobe is an organism that makes ATP by aerobic respiration if oxygen is present, but is capable of switching to fermentation if oxygen is absent.
Gram-negative bacteria are bacteria that do not retain the crystal violet stain used in the gram-staining method of bacterial differentiation. They are characterized by their cell envelopes, which are composed of a thin peptidoglycan cell wall sandwiched between an inner cytoplasmic cell membrane and a bacterial outer membrane.
The Enterobacteriaceae are a large family of Gram-negative bacteria. This family is the only representative in the order Enterobacteriales of the class Gammaproteobacteria in the phylum Proteobacteria.
C. freundii is a common component of the gut microbiome of healthy humans.While most strains are beneficial, there are significant phenotypic variations among strains, even those that share >99% of their genome. Some rare strains of C. freundii have been associated with opportunistic nosocomial infections of the respiratory tract, urinary tract, blood, and many other normally sterile sites in immunocompromised patients.
C. freundii is also commonly found to be a member of the soil microbiome. This microbe plays an important role in the nitrogen cycle in the environment. C. freundii is responsible for reducing nitrate to nitrite in the environment.This conversion is an important and crucial stage in the nitrogen cycle.
The nitrogen cycle is the biogeochemical cycle by which nitrogen is converted into multiple chemical forms as it circulates among atmosphere, terrestrial, and marine ecosystems. The conversion of nitrogen can be carried out through both biological and physical processes. Important processes in the nitrogen cycle include fixation, ammonification, nitrification, and denitrification. The majority of Earth's atmosphere (78%) is atmosphere nitrogen, making it the largest source of nitrogen. However, atmospheric nitrogen has limited availability for biological use, leading to a scarcity of usable nitrogen in many types of ecosystems.
Nitrate is a polyatomic ion with the molecular formula NO−
3 and a molecular mass of 62.0049 u. Organic compounds that contain the nitrate ester as a functional group (RONO2) are also called nitrates.
The nitrite ion, which has the chemical formula NO−
2, is a symmetric anion with equal N–O bond lengths. Upon protonation, the unstable weak acid nitrous acid is produced. Nitrite can be oxidized or reduced, with the product somewhat dependent on the oxidizing/reducing agent and its strength. The nitrite ion is an ambidentate ligand, and is known to bond to metal centers in at least five different ways. Nitrite is also important in biochemistry as a source of the potent vasodilator nitric oxide. In organic chemistry the NO−
2 group is present in nitrous acid esters and nitro compounds. Nitrite is also used in the food production industry for curing meat.
C. freundii has also been investigated for biodegradation of tannic acid used in tanneries.
Biodegradation is the breakdown of organic matter by microorganisms, such as bacteria, fungi.
Tannic acid is a specific form of tannin, a type of polyphenol. Its weak acidity (pKa around 6) is due to the numerous phenol groups in the structure. The chemical formula for commercial tannic acid is often given as C76H52O46, which corresponds with decagalloyl glucose, but in fact it is a mixture of polygalloyl glucoses or polygalloyl quinic acid esters with the number of galloyl moieties per molecule ranging from 2 up to 12 depending on the plant source used to extract the tannic acid. Commercial tannic acid is usually extracted from any of the following plant parts: Tara pods (Caesalpinia spinosa), gallnuts from Rhus semialata or Quercus infectoria or Sicilian Sumac leaves (Rhus coriaria).
C. freundii has the ability to grow on glycerol, and use it as its sole source of carbon and energy. The organism contains a bacterial microcompartment which is capable of processing propanediol. C. freundii creates a positive MR and negative VP test along with a positive Catalase and negative Oxidase test. C. freundii cannot hydrolyze starch, lipids, or gelatin.
Glycerol is a simple polyol compound. It is a colorless, odorless, viscous liquid that is sweet-tasting and non-toxic. The glycerol backbone is found in many lipids which are known as glycerides. It is widely used in the food industry as a sweetener and humectant and in pharmaceutical formulations. Glycerol has three hydroxyl groups that are responsible for its solubility in water and its hygroscopic nature.
Propanediol may refer to either of three isomeric organic chemical compounds:
Lactobacillus is a genus of Gram-positive, facultative anaerobic or microaerophilic, rod-shaped, non-spore-forming bacteria. They are a major part of the lactic acid bacteria group. In humans, they constitute a significant component of the microbiota at a number of body sites, such as the digestive system, urinary system, and genital system. In women of European ancestry, Lactobacillus species are normally a major part of the vaginal microbiota. Lactobacillus forms biofilms in the vaginal and gut microbiota, allowing them to persist during harsh environmental conditions and maintain ample populations. Lactobacillus exhibits a mutualistic relationship with the human body, as it protects the host against potential invasions by pathogens, and in turn, the host provides a source of nutrients. Lactobacillus is the most common probiotic found in food such as yogurt, and it is diverse in its application to maintain human well-being, as it can help treat diarrhea, vaginal infections, and skin disorders such as eczema.
The human microbiota is the aggregate of microorganisms that resides on or within any of a number of human tissues and biofluids, including the skin, mammary glands, placenta, seminal fluid, uterus, ovarian follicles, lung, saliva, oral mucosa, conjunctiva, biliary and gastrointestinal tracts. They include bacteria, archaea, fungi, protists and viruses. Though micro-animals can also live on the human body, they are typically excluded from this definition. The human microbiome refers specifically to the collective genomes of resident microorganisms.
Lipopolysaccharides (LPS), also known as lipoglycans and endotoxins, are large molecules consisting of a lipid and a polysaccharide composed of O-antigen, outer core and inner core joined by a covalent bond; they are found in the outer membrane of Gram-negative bacteria.
The term broad-spectrum antibiotic can refer to an antibiotic that acts on the two major bacterial groups, gram-positive and gram-negative, or any antibiotic that acts against a wide range of disease-causing bacteria. These medications are used when a bacterial infection is suspected but the group of bacteria is unknown or when infection with multiple groups of bacteria is suspected. This is in contrast to a narrow-spectrum antibiotic, which is effective against only a specific group of bacteria. Although powerful, broad-spectrum antibiotics pose specific risks, particularly the disruption of native, normal bacteria and the development of antimicrobial resistance. An example of a commonly used broad-spectrum antibiotic is ampicillin.
Campylobacter jejuni is one of the most common causes of food poisoning in Europe and in The United States. The vast majority of cases occur as isolated events, not as part of recognized outbreaks. Active surveillance through the Foodborne Diseases Active Surveillance Network (FoodNet) indicates that about 14 cases are diagnosed each year for each 100,000 persons in the population. The European Food Safety Authority estimated in 2011 that there are approximately nine million cases of human campylobacteriosis per year in the European Union.
Klebsiella is a genus of nonmotile, Gram-negative, oxidase-negative, rod-shaped bacteria with a prominent polysaccharide-based capsule.
Proteus mirabilis is a Gram-negative, facultatively anaerobic, rod-shaped bacterium. It shows swarming motility and urease activity. P. mirabilis causes 90% of all Proteus infections in humans. It is widely distributed in soil and water.
Gut flora, or gut microbiota, or gastrointestinal microbiota, is the complex community of microorganisms that live in the digestive tracts of humans and other animals, including insects. The gut metagenome is the aggregate of all the genomes of gut microbiota. The gut is one niche that human microbiota inhabit.
Citrobacter is a genus of Gram-negative coliform bacteria in the Enterobacteriaceae family.
Dysbiosis is a term for a microbial imbalance or maladaptation on or inside the body, such as an impaired microbiota. For example, a part of the human microbiota, such as the skin flora, gut flora, or vaginal flora, can become deranged, with normally dominating species underrepresented and normally outcompeted or contained species increasing to fill the void. Dysbiosis is most commonly reported as a condition in the gastrointestinal tract, particularly during small intestinal bacterial overgrowth (SIBO) or small intestinal fungal overgrowth (SIFO).
The term skin flora refers to the microorganisms which reside on the skin, typically human skin.
The Human Microbiome Project (HMP) was a United States National Institutes of Health (NIH) research initiative to improve understanding of the microbial flora involved in human health and disease. Launched in 2007, the first phase (HMP1) focused on identifying and characterizing human microbial flora. The second phase, known as the Integrative Human Microbiome Project (iHMP) launched in 2014 with the aim of generating resources to characterize the microbiome and elucidating the roles of microbes in health and disease states. The program received $170 million in funding by the NIH Common Fund from 2007 to 2016.
A microbiota is an "ecological community of commensal, symbiotic and pathogenic microorganisms" found in and on all multicellular organisms studied to date from plants to animals. A microbiota includes bacteria, archaea, protists, fungi and viruses. Microbiota have been found to be crucial for immunologic, hormonal and metabolic homeostasis of their host. The synonymous term microbiome describes either the collective genomes of the microorganisms that reside in an environmental niche or the microorganisms themselves.
Prevotella is a genus of Gram-negative bacteria.
Clostridium cadaveris is an enteric, gas-forming, motile, strictly anaerobic gram-positive bacterium of the genus Clostridium. First described by Klein in 1899, it was noted to be the most prominent bacteria during human decomposition; historically it was described as "putrefying flora".
Escherichia coli ( Anglicized to ; commonly abbreviated E. coli) is a gram-negative, rod-shaped bacterium that is commonly found in the lower intestine of warm-blooded organisms (endotherms). Most E. coli strains are harmless, but some serotypes are pathogenic and can cause serious food poisoning in humans, and are occasionally responsible for product recalls. E. coli are also responsible for a majority of cases of urinary tract infections. The harmless strains are part of the normal flora of the gut, and can benefit their hosts by producing vitamin K2, and by preventing the establishment of pathogenic bacteria within the intestine.
Bacteriotherapy is the purposeful use of bacteria or their products in treating an illness. Forms of bacteriotherapy include the use of probiotics, microorganisms that provide health benefits when consumed; fecal matter transplants (FMT) /intestinal microbiota transplant (IMT), the transfer of gut microorganisms from the fecal matter of healthy donors to recipient patients to restore microbiota; or synbiotics which combine prebiotics, indigestible ingredients that promote growth of beneficial microorganisms, and probiotics. Through these methods, the gut microbiota, the community of 300-500 microorganism species that live in the digestive tract of animals aiding in digestion, energy storage, immune function and protection against pathogens, can be recolonized with favorable bacteria, which in turn has therapeutic effects.
Citrobacter sedlakii is a species of Gram-negative bacteria. It has been described as causing human disease, but is generally found as a non-pathogenic organism in human stools.
The uterine microbiome is the commensal, nonpathogenic, bacteria, viruses, yeasts/fungi present in a healthy uterus, amniotic fluid and endometrium and the specific environment which they inhabit. It has been only recently confirmed that the uterus and its tissues are not sterile. Due to improved 16S rRNA gene sequencing techniques, detection of bacteria that are present in low numbers is possible. Using this procedure that allows the detection of bacteria that cannot be cultured outside the body, studies of microbiota present in the uterus are expected to increase.
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