''Candida'' is a
genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...
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 constitut ...
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 ti ...
worldwide. Many species are harmless
commensals
Commensalism is a long-term biological interaction (symbiosis) in which members of one species gain benefits while those of the other species neither benefit nor are harmed. This is in contrast with mutualism, in which both organisms benefit fro ...
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 splinte ...
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 immune ...
.
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 us ...
'' 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 fermentation into alcohol, and the bottling of the finished liquid. The history of wine-making stretches over millennia. The science of wine and ...
, 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 gut mi ...
, 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), fur or ...
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 a ...
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 candidias ...
), 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 that a ...
), 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 ge ...
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 of ...
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 immune ...
, 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 flavono ...
'' 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 is ...
'' 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 tr ...
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 ha ...
'' 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 ...
'' 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 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 the power of the ...
) 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 wil ...
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, using ...
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 two- ...
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 refined ...
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 suffix '' - ...
, 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 converg ...
(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 constitut ...
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
''Meyerozyma guilliermondii'' (formerly known as ''Pichia guilliermondii'' until its rename in 2010) is a species of yeast of the genus '' Meyerozyma'' whose asexual or anamorphic form is known as ''Candida guilliermondii''.
''Candida guillierm ...
'', and ''Candida lusitaniae
''Candida lusitaniae'' is a species 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 cu ...
'' 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 nomenclat ...
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 (linguistic), meaning of a #Source and target languages, source-language text by means of an Dynamic and formal equivalence, equivalent #Source and target languages, target-language text. The ...
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 am ...
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.
A p ...
. 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- ca ...
) 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 un ...
. 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 ac ...
(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 monophosphate (c ...
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 ac ...
. 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 other ...
(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 nuclei ...
). 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 Protein biosynthesis, synthesizing a protein.
mRNA is ...
, 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 & Connec ...
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. Bacte ...
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 heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation ...
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 within ...
.
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 cuticle, animal coverings, such as the arthropod exoskeleton, have diffe ...
[ 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'' is ...
, to systemic, such as fungemia
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 a ...
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 candidias ...
. 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 crypt ...
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 fee ...
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 itch ...
). 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 s ...
, 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 the ...
, 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 bacteria ...
(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 in ...
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 prevent ...
; 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 nan ...
(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. Th ...
-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 invo ...
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