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''Candida'' is a
genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial no ...
of
yeast Yeasts are eukaryotic, single-celled microorganisms classified as members of the fungus kingdom. The first yeast originated hundreds of millions of years ago, and at least 1,500 species are currently recognized. They are estimated to constit ...
s and is the most common cause of
fungal infections Fungal infection, also known as mycosis, is disease caused by fungi. Different types are traditionally divided according to the part of the body affected; superficial, subcutaneous, and systemic. Superficial fungal infections include common ...
worldwide. Many species are harmless commensals or
endosymbiont An ''endosymbiont'' or ''endobiont'' is any organism that lives within the body or cells of another organism most often, though not always, in a mutualistic relationship. (The term endosymbiosis is from the Greek: ἔνδον ''endon'' "within" ...
s of hosts including
human Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, culture, ...
s; however, when
mucosal A mucous membrane or mucosa is a membrane that lines various cavities in the body of an organism and covers the surface of internal organs. It consists of one or more layers of epithelial cells overlying a layer of loose connective tissue. It is ...
barriers are disrupted or the
immune system The immune system is a network of biological processes that protects an organism from diseases. It detects and responds to a wide variety of pathogens, from viruses to parasitic worms, as well as cancer cells and objects such as wood splint ...
is compromised they can invade and cause disease, known as an
opportunistic infection An opportunistic infection is an infection caused by pathogens (bacteria, fungi, parasites or viruses) that take advantage of an opportunity not normally available. These opportunities can stem from a variety of sources, such as a weakened imm ...
. Candida is located on most mucosal surfaces and mainly the gastrointestinal tract, along with the skin. ''
Candida albicans ''Candida albicans'' is an opportunistic pathogenic yeast that is a common member of the human gut flora. It can also survive outside the human body. It is detected in the gastrointestinal tract and mouth in 40–60% of healthy adults. It is usu ...
'' is the most commonly isolated species and can cause infections (
candidiasis Candidiasis is a fungal infection due to any type of '' Candida'' (a type of yeast). When it affects the mouth, in some countries it is commonly called thrush. Signs and symptoms include white patches on the tongue or other areas of the mouth ...
or thrush) in humans and other animals. In
winemaking Winemaking or vinification is the production of wine, starting with the selection of the fruit, its Ethanol fermentation, fermentation into alcohol, and the bottling of the finished liquid. The history of wine-making stretches over millennia. The ...
, some species of ''Candida'' can potentially spoil wines. Many species are found in
gut flora Gut microbiota, gut microbiome, or gut flora, are the microorganisms, including bacteria, archaea, fungi, and viruses that live in the digestive tracts of animals. The gastrointestinal metagenome is the aggregate of all the genomes of the gu ...
, including ''C. albicans'' in
mammal Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fu ...
ian hosts, whereas others live as endosymbionts in insect hosts. Systemic infections of the bloodstream and major organs (
candidemia Fungemia is the presence of fungi or yeasts in the blood. The most common type, also known as candidemia, candedemia, or systemic candidiasis, is caused by '' Candida'' species; candidemia is also among the most common bloodstream infections of ...
or
invasive candidiasis Invasive candidiasis is an infection (candidiasis) that can be caused by various species of ''Candida'' yeast. Unlike ''Candida'' infections of the mouth and throat ( oral candidiasis) or vagina ( ''Candidal'' vulvovaginitis), invasive candidia ...
), particularly in patients with an impaired immune system (
immunocompromised Immunodeficiency, also known as immunocompromisation, is a state in which the immune system's ability to fight infectious diseases and cancer is compromised or entirely absent. Most cases are acquired ("secondary") due to extrinsic factors tha ...
), affect over 90,000 people a year in the US. The
genome In the fields of molecular biology and genetics, a genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding ...
of several ''Candida'' species has been sequenced.
Antibiotic An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting bacterial infections, and antibiotic medications are widely used in the treatment and prevention ...
s promote yeast (fungal) infections, including gastrointestinal (GI) ''Candida'' overgrowth and penetration of the GI mucosa. While women are more susceptible to genital yeast infections, men can also be infected. Certain factors, such as prolonged antibiotic use, increase the risk for both men and women. People with
diabetes Diabetes, also known as diabetes mellitus, is a group of metabolic disorders characterized by a high blood sugar level (hyperglycemia) over a prolonged period of time. Symptoms often include frequent urination, increased thirst and increased ap ...
or the immunocompromised, such as those infected with
HIV The human immunodeficiency viruses (HIV) are two species of ''Lentivirus'' (a subgroup of retrovirus) that infect humans. Over time, they cause acquired immunodeficiency syndrome (AIDS), a condition in which progressive failure of the immu ...
, are more susceptible to yeast infections. ''
Candida antarctica ''Candida antarctica'' is a yeast species in the genus '' Candida''. ''Candida antarctica'' is a source of important industrial enzymes. Immobilized ''Candida antarctica'' lipase can be used to catalyze the regioselective acylation of flavonoi ...
'' and ''
Candida rugosa ''Candida'' is a genus of yeasts and is the most common cause of fungal infections worldwide. Many species are harmless commensals or endosymbionts of hosts including humans; however, when mucosal barriers are disrupted or the immune system ...
'' are a source of industrially important
lipase Lipase ( ) is a family of enzymes that catalyzes the hydrolysis of fats. Some lipases display broad substrate scope including esters of cholesterol, phospholipids, and of lipid-soluble vitamins and sphingomyelinases; however, these are usually t ...
s, while ''
Candida krusei ''Candida krusei'' is a budding yeast (a species of fungus) involved in chocolate production. ''Candida krusei'' is an emerging fungal nosocomial pathogen primarily found in the immunocompromised and those with hematological malignancies. It ...
'' is prominently used to ferment cacao during chocolate production. ''
Candida rugosa ''Candida'' is a genus of yeasts and is the most common cause of fungal infections worldwide. Many species are harmless commensals or endosymbionts of hosts including humans; however, when mucosal barriers are disrupted or the immune system ...
'' is also used as an enzyme supplement to support fat digestion with its broad specificity for lipid hydrolysis.


Biology

When grown in a
laboratory A laboratory (; ; colloquially lab) is a facility that provides controlled conditions in which scientific or technological research, experiments, and measurement may be performed. Laboratory services are provided in a variety of settings: physicia ...
, ''Candida'' appears as large, round, white or cream (''albicans'' means "whitish" in
Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through ...
) colonies, which emit a yeasty odor on
agar plate An agar plate is a Petri dish that contains a growth medium solidified with agar, used to culture microorganisms. Sometimes selective compounds are added to influence growth, such as antibiotics. Individual microorganisms placed on the plate wi ...
s at room temperature. ''C. albicans'' ferments
glucose Glucose is a simple sugar with the molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, u ...
and
maltose } Maltose ( or ), also known as maltobiose or malt sugar, is a disaccharide formed from two units of glucose joined with an α(1→4) bond. In the isomer isomaltose, the two glucose molecules are joined with an α(1→6) bond. Maltose is the ...
to acid and gas,
sucrose Sucrose, a disaccharide, is a sugar composed of glucose and fructose subunits. It is produced naturally in plants and is the main constituent of white sugar. It has the molecular formula . For human consumption, sucrose is extracted and refi ...
to acid, and does not ferment
lactose Lactose is a disaccharide sugar synthesized by galactose and glucose subunits and has the molecular formula C12H22O11. Lactose makes up around 2–8% of milk (by mass). The name comes from ' (gen. '), the Latin word for milk, plus the suffi ...
, which helps to distinguish it from other ''Candida'' species. Recent molecular
phylogenetic In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...
studies show that the genus ''Candida'', as currently defined, is extremely
polyphyletic A polyphyletic group is an assemblage of organisms or other evolving elements that is of mixed evolutionary origin. The term is often applied to groups that share similar features known as homoplasies, which are explained as a result of conver ...
(encompassing distantly-related species that do not form a natural group). Before the advent of inexpensive molecular methods,
yeast Yeasts are eukaryotic, single-celled microorganisms classified as members of the fungus kingdom. The first yeast originated hundreds of millions of years ago, and at least 1,500 species are currently recognized. They are estimated to constit ...
s that were isolated from infected patients were often called ''Candida'' without clear evidence of relationship to other ''Candida'' species. For example, ''
Candida glabrata ''Candida glabrata'' is a species of haploid yeast of the genus ''Candida'', previously known as ''Torulopsis glabrata''. Despite the fact that no sexual life cycle has been documented for this species, ''C. glabrata'' strains of both mating typ ...
'', '' Candida guilliermondii'', and '' Candida lusitaniae'' are clearly misclassified and will be placed in other
genera Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomencla ...
once phylogenetic reorganization is complete (for example, see Khunnamwong ''et al.'' 2015). Some species of ''Candida'' use a non-standard
genetic code The genetic code is the set of rules used by living cells to translate information encoded within genetic material ( DNA or RNA sequences of nucleotide triplets, or codons) into proteins. Translation is accomplished by the ribosome, which links ...
in the
translation Translation is the communication of the meaning of a source-language text by means of an equivalent target-language text. The English language draws a terminological distinction (which does not exist in every language) between ''transl ...
of their
nuclear gene A nuclear gene is a gene whose physical DNA nucleotide sequence is located in the cell nucleus of a eukaryote. The term is used to distinguish nuclear genes from genes found in mitochondria or chloroplasts. The vast majority of genes in eukaryote ...
s into the
amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha a ...
sequences of
polypeptides Peptides (, ) are short chains of amino acids linked by peptide bonds. Long chains of amino acids are called proteins. Chains of fewer than twenty amino acids are called oligopeptides, and include dipeptides, tripeptides, and tetrapeptides. ...
. The difference in the genetic code between species possessing this alternative code is that the
codon The genetic code is the set of rules used by living cells to translate information encoded within genetic material ( DNA or RNA sequences of nucleotide triplets, or codons) into proteins. Translation is accomplished by the ribosome, which links ...
CUG (normally encoding the amino acid
leucine Leucine (symbol Leu or L) is an essential amino acid that is used in the biosynthesis of proteins. Leucine is an α-amino acid, meaning it contains an α- amino group (which is in the protonated −NH3+ form under biological conditions), an α- ...
) is translated by the yeast as a different amino acid,
serine Serine (symbol Ser or S) is an α-amino acid that is used in the biosynthesis of proteins. It contains an α-amino group (which is in the protonated − form under biological conditions), a carboxyl group (which is in the deprotonated − form ...
. The alternative translation of the CUG codon in these species is due to a novel nucleic acid sequence in the serine-
tRNA Transfer RNA (abbreviated tRNA and formerly referred to as sRNA, for soluble RNA) is an adaptor molecule composed of RNA, typically 76 to 90 nucleotides in length (in eukaryotes), that serves as the physical link between the mRNA and the amino ...
(ser-tRNACAG), which has a
guanosine Guanosine (symbol G or Guo) is a purine nucleoside comprising guanine attached to a ribose ( ribofuranose) ring via a β-N9- glycosidic bond. Guanosine can be phosphorylated to become guanosine monophosphate (GMP), cyclic guanosine monophospha ...
located at position 33, 5' to the
anticodon Transfer RNA (abbreviated tRNA and formerly referred to as sRNA, for soluble RNA) is an adaptor molecule composed of RNA, typically 76 to 90 nucleotides in length (in eukaryotes), that serves as the physical link between the mRNA and the amino a ...
. In all other tRNAs, this position is normally occupied by a
pyrimidine Pyrimidine (; ) is an aromatic, heterocyclic, organic compound similar to pyridine (). One of the three diazines (six-membered heterocyclics with two nitrogen atoms in the ring), it has nitrogen atoms at positions 1 and 3 in the ring. The oth ...
(often
uridine Uridine ( symbol U or Urd) is a glycosylated pyrimidine analog containing uracil attached to a ribose ring (or more specifically, a ribofuranose) via a β-N1-glycosidic bond. The analog is one of the five standard nucleosides which make up ...
). This genetic code change is the only such known alteration in cytoplasmic
mRNA In molecular biology, messenger ribonucleic acid (mRNA) is a single-stranded molecule of RNA that corresponds to the genetic sequence of a gene, and is read by a ribosome in the process of synthesizing a protein. mRNA is created during t ...
, in both the
prokaryote A prokaryote () is a single-celled organism that lacks a nucleus and other membrane-bound organelles. The word ''prokaryote'' comes from the Greek πρό (, 'before') and κάρυον (, 'nut' or 'kernel').Campbell, N. "Biology:Concepts & Con ...
s, and the
eukaryote Eukaryotes () are organisms whose cells have a nucleus. All animals, plants, fungi, and many unicellular organisms, are Eukaryotes. They belong to the group of organisms Eukaryota or Eukarya, which is one of the three domains of life. Bact ...
s, involving the reassignment of a sense codon. This novel genetic code may be a mechanism for more rapid adaptation to the organism's environment, as well as playing an important role in the
evolution Evolution is change in the heredity, heritable Phenotypic trait, characteristics of biological populations over successive generations. These characteristics are the Gene expression, expressions of genes, which are passed on from parent to ...
of the genus ''Candida'' by creating genetic barriers that encouraged
speciation Speciation is the evolutionary process by which populations evolve to become distinct species. The biologist Orator F. Cook coined the term in 1906 for cladogenesis, the splitting of lineages, as opposed to anagenesis, phyletic evolution withi ...
.


Pathogen

''Candida'' are almost universal in low numbers on healthy adult
skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Other animal coverings, such as the arthropod exoskeleton, have different d ...
and ''C.'' ''albicans'' is part of the normal flora of the mucous membranes of the respiratory, gastrointestinal and female genital tracts. The dryness of skin compared to other tissues prevents the growth of the fungus, but damaged skin or skin in
intertriginous In medicine, an intertriginous area is where two skin areas may touch or rub together. Examples of intertriginous areas are the axilla of the arm, the anogenital region, skin folds of the breasts and between digits. Intertriginous areas are known t ...
regions is more amenable to rapid growth. Overgrowth of several species, including ''C.'' ''albicans'', can cause infections ranging from superficial, such as oropharyngeal candidiasis (thrush) or
vulvovaginal candidiasis Vaginal yeast infection, also known as candidal vulvovaginitis and vaginal thrush, is excessive growth of yeast in the vagina that results in irritation. The most common symptom is vaginal itching, which may be severe. Other symptoms include burn ...
(vaginal candidiasis) and subpreputial candidiasis, which may cause
balanitis Balanitis is inflammation of the glans penis. When the foreskin is also affected, the proper term is balanoposthitis. Balanitis on boys still in diapers must be distinguished from redness caused by ammoniacal dermatitis. The word ''balanitis'' ...
, to systemic, such as fungemia and
invasive candidiasis Invasive candidiasis is an infection (candidiasis) that can be caused by various species of ''Candida'' yeast. Unlike ''Candida'' infections of the mouth and throat ( oral candidiasis) or vagina ( ''Candidal'' vulvovaginitis), invasive candidia ...
. Oral candidiasis is common in elderly
denture Dentures (also known as false teeth) are prosthetic devices constructed to replace missing teeth, and are supported by the surrounding soft and hard tissues of the oral cavity. Conventional dentures are removable (removable partial denture or ...
-wearers. In otherwise healthy individuals, these superficial infections can be cured with topical or systemic
antifungal medication An antifungal medication, also known as an antimycotic medication, is a pharmaceutical fungicide or fungistatic used to treat and prevent mycosis such as athlete's foot, ringworm, candidiasis (thrush), serious systemic infections such as cr ...
s (commonly over-the-counter antifungal treatments like
miconazole Miconazole, sold under the brand name Monistat among others, is an antifungal medication used to treat ring worm, pityriasis versicolor, and yeast infections of the skin or vagina. It is used for ring worm of the body, groin (jock itch), and ...
or
clotrimazole Clotrimazole, sold under the brand name Lotrimin, among others, is an antifungal medication. It is used to treat vaginal yeast infections, oral thrush, diaper rash, tinea versicolor, and types of ringworm including athlete's foot and jock it ...
). In debilitated or immunocompromised patients, or if introduced intravenously (into the
bloodstream The blood circulatory system is a system of organs that includes the heart, blood vessels, and blood which is circulated throughout the entire body of a human or other vertebrate. It includes the cardiovascular system, or vascular system, tha ...
), candidiasis may become a systemic disease producing
abscess An abscess is a collection of pus that has built up within the tissue of the body. Signs and symptoms of abscesses include redness, pain, warmth, and swelling. The swelling may feel fluid-filled when pressed. The area of redness often extends b ...
es,
thrombophlebitis Thrombophlebitis is a phlebitis (inflammation of a vein) related to a thrombus (blood clot). When it occurs repeatedly in different locations, it is known as thrombophlebitis migrans ( migratory thrombophlebitis). Signs and symptoms The following ...
,
endocarditis Endocarditis is an inflammation of the inner layer of the heart, the endocardium. It usually involves the heart valves. Other structures that may be involved include the interventricular septum, the chordae tendineae, the mural endocardium, or ...
, or infections of the eyes or other organs. Typically, relatively severe
neutropenia Neutropenia is an abnormally low concentration of neutrophils (a type of white blood cell) in the blood. Neutrophils make up the majority of circulating white blood cells and serve as the primary defense against infections by destroying bacter ...
(low
neutrophil Neutrophils (also known as neutrocytes or heterophils) are the most abundant type of granulocytes and make up 40% to 70% of all white blood cells in humans. They form an essential part of the innate immune system, with their functions varying i ...
s) is a prerequisite for ''Candida'' to pass through the defenses of the skin and cause disease in deeper tissues; in such cases, mechanical disruption of the infected skin sites is typically a factor in the fungal invasion of the deeper tissues. The most common way to treat invasive candida infections is with the use of
amphotericin Amphotericin B is an antifungal medication used for serious fungal infections and leishmaniasis. The fungal infections it is used to treat include mucormycosis, aspergillosis, blastomycosis, candidiasis, coccidioidomycosis, and cryptococcosis. ...
or
fluconazole Fluconazole is an antifungal medication used for a number of fungal infections. This includes candidiasis, blastomycosis, coccidiodomycosis, cryptococcosis, histoplasmosis, dermatophytosis, and pityriasis versicolor. It is also used to pre ...
; other methods would include surgery.


Applications

''C. albicans'' has been used in combination with
carbon nanotubes A scanning tunneling microscopy image of a single-walled carbon nanotube Rotating single-walled zigzag carbon nanotube A carbon nanotube (CNT) is a tube made of carbon with diameters typically measured in nanometers. ''Single-wall carbon na ...
(CNT) to produce stable electrically-conductive bio-nano-composite tissue materials that have been used as temperature-sensing elements.


Species

Among ''Candida'' species, ''C. albicans'', which is a normal constituent of the
human flora The human microbiome is the aggregate of all microbiota that reside on or within human tissues and biofluids along with the corresponding anatomical sites in which they reside, including the skin, mammary glands, seminal fluid, uterus, ovarian ...
, a commensal of the skin and the gastrointestinal and genitourinary tracts, is responsible for the majority of ''Candida'' bloodstream infections (candidemia). Yet, there is an increasing incidence of infections caused by '' C. glabrata'' and '' C. rugosa'', which could be because they are frequently less susceptible to the currently used
azole Azoles are a class of five-membered heterocyclic compounds containing a nitrogen atom and at least one other non-carbon atom (i.e. nitrogen, sulfur, or oxygen) as part of the ring. Their names originate from the Hantzsch–Widman nomenclature ...
-group of antifungals. Other medically important species include '' C. parapsilosis'', '' C. tropicalis'', '' C. dubliniensis''. and the more recent upcoming pathogen '' C. auris''. Other ''Candida'' species, such as '' C. oleophila'', have been used as
biological control Biological control or biocontrol is a method of controlling pests, such as insects, mites, weeds, and plant diseases, using other organisms. It relies on predation, parasitism, herbivory, or other natural mechanisms, but typically also in ...
agents in fruit. * '' C. albicans'' * '' C. ascalaphidarum'' * '' C. amphixiae'' * '' C. antarctica'' * '' C. argentea'' * '' C. atlantica'' * '' C. atmosphaerica'' * '' C. auris'' * '' C. blankii'' * '' C. blattae'' * '' C. bracarensis'' * '' C. bromeliacearum'' * '' C. carpophila'' * '' C. carvajalis'' * '' C. catenulata'' * '' C. cerambycidarum'' * '' C. chauliodes'' * '' C. corydali'' * '' C. crusei'' * '' C. dosseyi'' * '' C. dubliniensis'' * '' C. ergatensis'' * '' C. fructus'' * '' C. glabrata'' * '' C. fermentati'' * '' C. guilliermondii'' * '' C. haemulonii'' * '' C. humilis'' * '' C. insectamens'' * '' C. insectorum'' * '' C. intermedia'' * '' C. jeffresii'' * '' C. kefyr'' * '' C. keroseneae'' * '' C. krusei'' * '' C. lusitaniae'' * '' C. lyxosophila'' * '' C. maltosa'' * '' C. marina'' * '' C. membranifaciens'' * '' C. mogii'' * '' C. oleophila'' * '' C. oregonensis'' * '' C. parapsilosis'' * '' C. quercitrusa'' * '' C. rhizophoriensis'' * '' C. rugosa'' * '' C. sake'' * '' C. sharkiensis'' * '' C. shehatea'' * '' C. temnochilae'' * '' C. tenuis'' * '' C. theae'' * '' C. tolerans'' * '' C. tropicalis'' * '' C. tsuchiyae'' * '' C. sinolaborantium'' * '' C. sojae'' * '' C. subhashii'' * '' C. viswanathii'' * '' C. ubatubensis'' * '' C. utilis'' * '' C. zemplinina''


References


External links


Labs working on Candida
* {{Authority control Yeasts Gut flora Pathogenic microbes