Generality
Molds are eukaryotic organisms, consisting of more than one cell and belonging to the kingdom of fungi.
Heterotrophic living beings, molds can have toxic, allergic or pathogenic properties towards human beings.
The hyphae are the filamentous structures that constitute the so-called mycelium (or vegetative body).
Under certain environmental conditions, many molds can become yeasts; this capacity is called dimorphism and the mushrooms that are its protagonists take on the name of dimorphic mushrooms.
The main molds with toxic, allergic or pathogenic properties for humans and other animals include: Stachybotrys chartarum, Cladosporium herbarum, Aspergillus fumigatus, some muffins of the genus Trichophyton, Penicillium marneffei and Histoplasma capsulatum .
Short reference to mushrooms
Fungi constitute a realm of eukaryotic living organisms, whose cells have some characteristics of animal cells (mitochondria, heterotrophy, etc.), some characteristics of plant cells (cell wall and vacuole) and some characteristics of bacterial cells (self-synthesis of 'amino acid L-lysine).
There are many types of fungi, from unicellular ones - that is, composed of only one cell - to multicellular ones - that is, made up of more than one cell; from those saprophytes to those parasites, from those edible to those pathogenic for the human being and not only etc.
Their history is very ancient; according to some studies, in fact, the first mushrooms would have been present on Earth already 3.5 billion years ago.
What are molds?
Molds (in the singular mold) are multicellular organisms, visible even to the naked eye, belonging to the kingdom of fungi .
There are many living molds on Earth: currently, experts say that the known species of mold are several thousand.
In this article, molds subject to greater attention are molds with toxic, allergic or pathogenic properties .
Molds with toxic, allergic or pathogenic properties are a particular category of fungi capable of causing, respectively, toxic reactions, allergic reactions or diseases in human beings or in other living beings.
Yeasts are other fungi with pathogenic (but not toxic or allergic!) Properties.
Unlike molds, yeasts are single- celled organisms, not visible to the naked eye; in other words, they are microorganisms.
Table showing the scientific classification of molds | |
Domain: | eukaryotic |
Kingdom: | mushrooms |
WHO TAKES CARE OF THE STUDY OF TOXIC, ALLERGIC OR PATOGENIAN MOLDS?
Molds with toxic, allergic or pathogenic properties and, in general, all fungi capable of causing disease in humans, are the subject of study of the branch of medicine known as medical mycology .
Mycology is the term that indicates the biomedical discipline that studies fungi in general.
WHAT KIND OF DISEASES DO THE PATOGENE MOLDS CAUSE?
The diseases caused by pathogenic molds (and in general by all fungi with pathogenic properties) are infectious diseases or infections .
In specialized parlance, mold infections and pathogenic fungi in general are called mycoses .
Fungal infections are many; to simplify the study, the doctors decided to classify them based on the site of infection. As a result, mycoses can be distinguished in 5 large groups (or types): superficial mycoses, cutaneous mycoses, subcutaneous mycoses (or subcutaneous mycoses ), systemic mycoses due to primary pathogens and systemic mycoses due to opportunistic pathogens .
The most famous pathogenic molds are usually responsible for cutaneous mycoses, subcutaneous mycoses or systemic mycoses (NB: systemic mycoses of both types).
Biology
Being fungi, molds are eukaryotic organisms. A eukaryotic organism is a living being whose cells possess:
- A specialized compartment, which takes the name of nucleus and which is the seat of DNA (or genetic material);
- A DNA organized in chromosomes ;
- A series of organelles and
- A complex system of intracellular phospholipid membranes .
Typically, molds have a thick cell wall, made up of 75% chitin and 25% protein / lipids.
THEY ARE HETEROTROFI ORGANISMS
Molds and fungi in general are heterotrophic organisms .
A heterotrophic organism is a living being incapable of synthesizing the organic substances necessary for life, starting from inorganic substances; in order to survive, heterotrophic organisms must feed on organic substances produced by other organisms.
Living beings capable of synthesizing organic substances from inorganic substances are called autotrophic organisms . In nature, the autotrophic organisms par excellence are the plants, which produce organic substances starting from inorganic substances through the photosynthesis process.
REPRODUCTION
All species of molds, from those with pathogenic properties to those with allergic properties and so on, have the peculiarity of reproducing by sporogenesis, ie through the production of spores .
Comparison with yeasts
All yeasts, both pathogenic and non-pathogenic, are characterized by two modes of reproduction: the so-called binary splitting and the so-called budding.
TYPICAL HABITATS
Most of the molds prefer warm and humid environments as an ideal habitat for their own growth and survival.
However, it is important to point out that there are molds capable of surviving without problems in environments considered hostile to life. For example, there are:
- Molds that survive without problems in very cold environments . These organisms are the molds that can live inside the refrigerators of the house or in the snowy grounds;
- Molds that survive without problems in dry environments and characterized by drought . These organisms are called xerophilous molds ;
- Molds that survive in contact with highly acid solvents, soaps with antibacterial properties and petroleum-derived products.
Where is the human being more likely to come into contact with molds?
Human beings are more likely to come into contact with molds, attending antique shops, saunas, greenhouses, mills, farms, flower shops and summer cottages.
MOLDS HAVE IFE
Molds have the ability to produce hyphae (singular ifa ).
The hyphae are the filamentous and multicellular structures, which, in all the fungi (excluding yeasts), form the so-called mycelium (or vegetative body ) and distinguish the fungal process known as vegetative growth .
Molds and fungi generally absorb nutrients through hyphae.
MOLDS CAN ALSO BE YEASTS: MUSHROOMS IN MUSHROOMS
In particular environmental conditions or in other circumstances, some species of mold can become yeasts. Molds capable of turning into yeasts are organisms that from multicellular become unicellular and lose their ability to produce hyphae, for the mycelium.
The ability of some fungi to be, on some occasions, molds and, in other yeasts, is called dimorphism ; the fungi that can be molds or yeasts, according to certain environmental conditions (eg: temperature, etc.), are called dimorphic mushrooms .
Dimorphism is a capacity that affects numerous fungi with allergic, toxic or pathogenic properties.
In biology, the term dimorphism refers to the phenomenon in which an individual of the same living species is able to assume two different aspects or forms.
A dimorphic individual, therefore, is a subject that can present itself in two different forms.
clinic
The medical conditions, which some molds can induce in humans, depend on various factors, including:
- The general state of health of the person who comes into contact with the dangerous mold e
- The state of growth and development of dangerous mold (for example, an environment that favors the growth of a certain mold, causes the latter to be more prone to cause health problems in a given individual).
MOLD WITH TOXIC PROPERTIES
Molds with toxic properties exert their toxic power, through the so-called mycotoxins (NB: the prefix "mico", before the word "toxins", indicates that they are the "fungus toxins").
Mycotoxins are secondary metabolites, which molds and all fungi with toxic properties produce when certain environmental conditions occur. This means that the production (or biosynthesis) of mycotoxins depends on factors such as: temperature, the presence of water in the surrounding environment, environmental pH, etc.
Generally, mycotoxins reside in the spores (which are the result of the sporogenesis process) and / or in the environmental substrate that hosted the mold with toxic properties, during the growth phase.
The toxic capacity of mycotoxins depends on the quantity of the latter: high quantities are much more dangerous than small or negligible quantities; even, the same mycotoxin can be lethal, in large doses, and almost without harmful effects, in small doses.
Mycotoxins deriving from molds with toxic properties can have effects on the liver (hepatotoxins), renal (nephrotoxins), neurological (neurotoxins) and / or immune (immunotoxins); furthermore, they can alter cellular DNA (mutations) and start tumor-type processes (mycotoxins with mutagenic, teratogenic and / or carcinogenic effects).
Mycotoxin intoxications take the specific name of mycotoxicosis .
Generally, to allow the entry of mycotoxins into the human body are: ingestion (of the toxic substance), dermal exposure (to the toxic substance) and inhalation (of the toxic substance).
| List of the most important mycotoxins that can be harmful to humans: |
Aflatoxin |
citrinin |
Ergot alkaloids |
fumonisin |
Ochratoxin |
Trichotocene (plural trichotocene) |
Zearalenone |
MOLD WITH ALLERGIC PROPERTIES
Molds can have allergic properties in people who have a particular hypersensitivity to spores, hyphae or hyphae fragments; in case of hypersensitivity towards them, spores, hyphae and hyphae fragments are to be considered as allergens .
The typical effects of mold with allergic properties are: eye irritation, nasal congestion, rhinorrhea, allergic rhinitis, allergic asthma, hypersensitivity pneumonia and / or extrinsic allergic alveolitis.
In general, exposure to small amounts of mold with allergic properties is without effect; in fact, exposure to high amounts is dangerous.
The access route to the human organism of molds with allergic properties is the respiratory tract . Therefore, it is the inhalation of allergens that causes the aforementioned effects.
MOLD WITH PATOGENE-INFECTIOUS PROPERTIES
Typically, molds and all fungi with pathogenic properties are harmless or infectious to healthy people, while they are very dangerous, so as to cause potentially lethal infections, for individuals who have an ineffective immune system .
The immune system is an organism's defensive barrier against threats from the external environment, such as viruses, bacteria, fungi etc., but also from the internal environment, such as cancer cells (the so-called "mad cells") ) or malfunctioning.
To affect the efficiency of the human immune system may be morbid conditions, such as AIDS (ie HIV infection) or taking certain drugs, such as corticosteroids, chemotherapeutic drugs or immunosuppressants.
Moreover, it is good to remember that an inefficient immune system is typically present in very young subjects (NB: it is not yet fully developed) and in very elderly subjects (NB: it undergoes a physiological decrease in efficacy).
Other conditions that can favor the development of an infection after contact with a potentially pathogenic mold are diabetes and inadequate intake or for long periods of antibiotics .
Examples
There are many varieties of mold with toxic, allergic or pathogenic properties. This chapter is dedicated to the most famous varieties, such as the Aspergillus fumigatus, the Penicillium marneffei, the Cladosporium carionii, the molds of the genus Trichophyton, the Stachybotrys chartarum etc.
SOME EXAMPLES OF MOLD WITH TOXIC PROPERTIES
Among the best known examples of mold with toxic properties, are:
- Stachybotrys chartarum : it is a black-green mold, which is found very frequently on the surface of plasterboard, cardboard, paper and gauze. Of gelatinous consistency, it prefers very humid and water-rich environments.
A mycotoxicosis from Stachybotrys chartarum is responsible for a broad symptomatic picture, which includes: respiratory problems, skin inflammation, bleeding, irritation of the mucous membranes, damage to internal organs, mental confusion, fatigue, nausea and depression of the immune system.
- Trichoderma longibrachiatum : it is a mold of the genus Trichoderma, which prefers very humid environments.
On humans, the toxic power of its mycotoxins depends on a particular amino acid, known as α-aminoisobutyric acid. This particular amino acid, in fact, is able to interfere with the potassium and sodium ion channels of the cell membranes of cardiomyocytes, pneumocytes and neurons.
The mycotoxins of Trichoderma longibrachiatum are, in fact, neurotoxins.
- Memnoniella echinata : is akin to Stachybotrys chartarum .
SOME EXAMPLES OF MOLDS WITH ALLERGIC PROPERTIES
Among the most well-known molds with allergic properties, the following stand out:
- Some molds of the Cladosporium . The most common example is Cladosporium herbarum .
- Some molds of the genus Alternaria . The typical example is Alternaria alternata .
- Some molds of the genus Penicillium . The classic example is Penicillium notatum .
- Some molds of the genus Aspergillus . The classic example is Aspergillus fumigatus .
SOME EXAMPLES OF MOLDS WITH PATOGENE / INFECTIOUS PROPERTIES
Among the best known molds with pathogenic / infectious properties, they deserve a quotation:
- Some molds of the genus Aspergillus, including the already mentioned Aspergillus fumigatus and Aspergillus flavus . The infection that results is a systemic mycosis of the type "systemic mycosis due to opportunistic bacteria", called Aspergillosis .
Aspergillosis is responsible, above all, for an inflammation of the respiratory tract, whose symptoms resemble those of pneumonia.
For people with inefficient immune systems, it is potentially lethal.
Access routes to the human body: respiratory tract, digestive system and vascular system.
- Penicillium marneffei : is a dimorphic fungus, which causes a systemic mycosis identified with the name of penicilliosis and falling within the typology of systemic mycoses due to opportunistic pathogens. Very frequent and potentially fatal among AIDS patients, the systemic mycoses induced by Penicillium marneffei generally cause fever, anemia, weight loss, papule-like skin lesions, generalized lymphadenopathy and hepatomegaly.
Access routes to the human body: respiratory tract, digestive system and vascular system.
- Blastomyces dermatitidis . It is a dimorphic fungus (therefore it exists both in the form of yeast and in the form of fungus), which causes a systemic mycosis identified with the name of blastomycosis and falling within the typology of systemic mycoses due to primary pathogens.
Blastomycosis is characterized by a symptomatology that resembles that of pneumonia (difficulty breathing, cough, chest pain, etc.), fever, hot flushes, joint pain, myalgia, headache, skin rash, weight loss, etc.
Access routes to the human body: respiratory tract.
- Histoplasma capsulatum : it is a dimorphic fungus that causes a systemic mycosis known as histoplasmosis and belonging to the type of systemic mycoses due to primary pathogens. Potentially lethal for AIDS patients and all people with reduced immune defenses, histoplasmosis is particularly characterized by symptoms in the lung.
Access routes to the human body: respiratory tract.
- Paracoccidioides brasiliensis : is a dimorphic fungus responsible for a systemic mycosis, known as paracoccidioidomycosis (or South American blastomycosis ) and belonging to the typology of systemic mycoses due to primary pathogens.
Paracoccidioidomycosis involves various organs and tissues of the body, including the lungs (most affected organs), arteries, spleen, bones and meninges.
The most common symptoms are fever, cough and weight loss.
Access routes to the human body: respiratory tract.
- Molds of the genus Trichophyton . Responsible cutaneous mycoses (or tigne ), the most known species of the genus Trichophyton are: Trichophyton rubrum, Trichophyton mentagrophyes and Trichophyton verrucosum .
Trichophyton rubrum causes a cutaneous (or ringworm) mycosis, at the level of feet, hands, groin and / or nails. Readers are reminded that fungal infections of the nails are better known as onychomycosis .
Trichophyton mentagrophyes is the infectious agent responsible for the condition known as athlete's foot . Athlete's foot is a cutaneous mycosis that affects the areas between the toes and causes: red and itchy skin, skin thickening, skin peeling, blistering, appearance of skin cracks, smelly feet and thicker nails.
Finally, Trichophyton verrucosum is responsible for cutaneous mycoses especially among horses, donkeys, dogs and sheep; only in rare cases does it also infect the human being. In the latter, it affects the scalp, causing alopecia or baldness . Typically, humans who contract Trichophyton verrucosum infections live in close contact with the categories of animals mentioned above.
Additional molds with pathogenic properties, which will be limited to indicating the kind and type of infection, are: molds Coccidioides immitis and Coccidioides posadasii - which cause coccidioidomycosis (or valley fever ) - and molds of the genus Zigomycota ( or Zygomycetes ) - which cause the so-called zygomycosis .
