''Cladosporium herbarum'' is a common
fungus
A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from th ...
found worldwide in organic and inorganic matter.
It is efficiently distributed in the air, where it exists as the most frequently occurring fungal species.
It can grow over a wide range of temperatures including very cold environments, giving it the ability to grow on refrigerated meat and form "black spots".
Its high prevalence in the air and production of
allergens
An allergen is a type of antigen that produces an abnormally vigorous immune response in which the immune system fights off a perceived threat that would otherwise be harmless to the body. Such reactions are called allergies.
In technical terms ...
makes ''C. herbarum'' an important exacerbant of
asthma
Asthma is a long-term inflammatory disease of the airways of the lungs. It is characterized by variable and recurring symptoms, reversible airflow obstruction, and easily triggered bronchospasms. Symptoms include episodes of wheezing, cou ...
and hay fever.
Prevalence
''Cladosporium herbarum'' is the
type species
In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen ...
of the genus ''Cladosporium''.
Its
spores
In biology, a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plants, algae, f ...
are highly prevalent in the air; the
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 ...
''Cladosporium'' is the dominant genus of spores found in the air, with the ''C. herbarum'' species contributing the highest percentage to this group.
These airborne spores are more common during the summer and fall seasons;
in the summer there can be as many as 15,000 spores per m
3 air of ''C. herbarum''.
''Cladosporium herbarum'' is also found all over the world on dead organic material, in the soil, and sometimes appears as a plant
parasite
Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has ...
.
It is also a common fungus found in indoor environments.
Growth
In young cultures, newly-formed spores show growth by budding into a large, multi-branched
mycelium
Mycelium (plural mycelia) is a root-like structure of a fungus consisting of a mass of branching, thread-like hyphae. Fungal colonies composed of mycelium are found in and on soil and many other substrate (biology), substrates. A typical single ...
.
It has an optimal growth temperature between and , with a maximum growth temperature between and .
It has been shown to grow at temperatures as low as ,
and ;
allowing it to grow actively (albeit slowly) on frozen materials.
''Cladosporium herbarum'' can also grow in dry environments (
xerophile
A xerophile () is an extremophilic organism that can grow and reproduce in conditions with a low availability of water, also known as water activity. Water activity (aw) is measured as the humidity above a substance relative to the humidity above p ...
).
''C. herbarum'' grows optimally at
pH 6 but tolerates environments with a pH as low as 4.4.
Conidium
A conidium ( ; ), sometimes termed an asexual chlamydospore or chlamydoconidium (), is an asexual, non-motile spore of a fungus. The word ''conidium'' comes from the Ancient Greek word for dust, ('). They are also called mitospores due to th ...
production is higher in wet than dry conditions.
The production of spores is inhibited by
rubratoxin B and
aflatoxin
Aflatoxins are various poisonous carcinogens and mutagens that are produced by certain molds, particularly ''Aspergillus'' species. The fungi grow in soil, decaying vegetation and various staple foodstuffs and commodities such as hay, sweetcorn ...
.
Its growth is inhibited in atmospheres of reduced oxygen
and increased carbon dioxide.
''Mycosphaerella tassiana'' is the sexual reproductive stage (
teleomorph
In mycology, the terms teleomorph, anamorph, and holomorph apply to portions of the life cycles of fungi in the phyla Ascomycota and Basidiomycota:
*Teleomorph: the sexual reproductive stage (morph), typically a fruiting body.
*Anamorph: an ase ...
) of ''C. herbarum''.
Morphology
Spores produced by ''C. herbarum'' can be lemon-shaped or cone-shaped, often composed of 2-4 cells (3-23 mm).
One-celled conidia (5.5-13 x 3.8-6 µm) also exist.
In culture, newly-formed spores appear mostly 1-celled, later forming tree-like colonies with multiple branches.
The stalks which produce ''C. herbarum'' spores are 250 µm long and 3-6 µm wide.
They appear swollen at the tip and in between cells, and have irregularly bent branches.
Under microscopy, these stalks appear pale or dark brown in color and have smooth or rough walls.
When submerged in fluid, they become brittle and break up completely into spores and rod-like fragments.
Colonies grown on
Czapek yeast extract agar (CYA) and malt extract agar (MEA) appear velvety or fluffy, with smooth or slightly wrinkled walls, and are green or brown in color.
The reverse side of the colony appears a darker green or grey/black.
Colonies can appear both sparse or densely grown.
At , colonies are 1-2 mm in diameter.
Habitat and ecology
This species is distributed worldwide, inhabiting polar, temperate, mediterranean, subtropical, tropical, forest, grassland, and arable soil regions.
It is found frequently in
wood
Wood is a porous and fibrous structural tissue found in the stems and roots of trees and other woody plants. It is an organic materiala natural composite of cellulose fibers that are strong in tension and embedded in a matrix of lignin th ...
exposed to soil, deep soil depths, and the highly nutritious soil directly surrounding the roots of plants (
rhizosphere
The rhizosphere is the narrow region of soil or substrate that is directly influenced by root secretions and associated soil microorganisms known as the root microbiome. Soil pores in the rhizosphere can contain many bacteria and other microor ...
).
It is one of the early colonizers on dying and dead plants (
saprobe
Saprotrophic nutrition or lysotrophic nutrition is a process of chemoheterotrophic extracellular digestion involved in the processing of decayed (dead or waste) organic matter. It occurs in saprotrophs, and is most often associated with fungi ( ...
), especially the leaves and stems of both aquatic and desert plant species (for example
ferns
A fern (Polypodiopsida or Polypodiophyta ) is a member of a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. The polypodiophytes include all living pteridophytes except th ...
and
mosses
Mosses are small, non-vascular flowerless plants in the taxonomic division Bryophyta (, ) ''sensu stricto''. Bryophyta (''sensu lato'', Schimp. 1879) may also refer to the parent group bryophytes, which comprise liverworts, mosses, and horn ...
).
It is the most common fungal species found on living leaves (given suitable conditions) and dead plant material in very moist environments.
It also has an adaptation to high salt concentrations
(has been found in high salinity sediments) and extremely dry areas (xerophilic).
''Cladosporium herbarum'' causes spoilage of fresh fruits and vegetables including yams, peaches, nectarines, apricots, plums, cherries, tomatoes, and melons.
Its common occurrence on fresh apples can lead to contamination of apple juice and fruit based products.
It has also been found in eggs, hazelnuts, cereals, chickpeas, soybeans, and frozen fruit pastries.
''Cladosporium herbarum'' can also spoil cheese and
pasteurized
Pasteurization American and British English spelling differences#-ise, -ize (-isation, -ization), or pasteurisation is a process of food preservation in which packaged and non-packaged foods (such as milk and fruit juices) are treated with mi ...
soft cheese, causing problems during its manufacturing.
Being able to survive at temperatures below freezing, ''C. herbarum'' can cause “black spot” spoilage of meat in cold storage (between and ).
It has been isolated from fresh, frozen, and processed meats.
''Cladosporium herbarum'' has been isolated from caterpillars, nests, feathers, pellets of free-living birds, nests of gerbils, bee honeycombs, internal organs of frogs, and earthworms.
It has also been found indoors on walls, wallpaper, textiles, rubber strips of window-frames, and bathrooms.
Increased release of ''C. herbarum'' spores is correlated with increasing temperatures, daylight, and declining humidity.
This species appears more frequently during the summer than the winter with peak concentrations of airborne spores found during the afternoon of a 24 hour cycle.
The spores are easily carried through the air and can be transported long distances including over oceans.
Pathogenicity
This fungus is non-
pathogenic
In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ ...
, but its ability to freely produce spores that are easily dispersed in air currents adds to its effect as a fungal airway allergen; it is one of the main fungal causes of asthma and hay fever in the Western Hemisphere.
More than 60
antigens
In immunology, an antigen (Ag) is a molecule or molecular structure or any foreign particulate matter or a pollen grain that can bind to a specific antibody or T-cell receptor. The presence of antigens in the body may trigger an immune response. ...
derived from ''C. herbarum'' have been detected, and 36 of these have
immunoglobulin E
Immunoglobulin E (IgE) is a type of antibody (or immunoglobulin (Ig) " isotype") that has been found only in mammals. IgE is synthesised by plasma cells. Monomers of IgE consist of two heavy chains (ε chain) and two light chains, with the ε c ...
(IgE) binding properties.
Most of these antigens are proteins found inside cells,
and eight of these antigens are members of the World Health Organization's official allergen list.
There is variation in allergen content between different strains of ''C. herbarum'' .
Toxic effects of ''C. herbarum'' on warm-blood animals have been reported when they were fed with heavily infected wheat.
It can produce a toxin causing
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 ...
damage in horses, and mycelium extracts are shown to have low-level toxicity in chicken embryos.
''C. herbarum'' is also
fungal
A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from th ...
plant pathogen. Its hosts include ''
Bryum
''Bryum'' is a genus of mosses in the family Bryaceae. It was considered the largest genus of mosses, in terms of the number of species (over 1000), until it was split into three separate genera in a 2005 publication. As of 2013, the classificat ...
'', ''
Buxbaumia'', ''
Gyroweissia'', ''
Tortula
''Tortula'' is a genus of mosses in the family Pottiaceae.
Species
There are different classifications for the species included in the genus.
The delimitation of genus Tortula is problematic and was subject to a number of alterations in the pas ...
'', and ''
Dicranella''.
It can cause
Cladosporium ear rot on corn.
Molecular genetics
Most often, ''C. herbarum'' conidia have 1 nucleus, but some can have 2 nuclei.
During
mitosis
In cell biology, mitosis () is a part of the cell cycle in which replicated chromosomes are separated into two new nuclei. Cell division by mitosis gives rise to genetically identical cells in which the total number of chromosomes is mainta ...
, 5 to 8 dot-like
chromosomes
A chromosome is a long DNA molecule with part or all of the genetic material of an organism. In most chromosomes the very long thin DNA fibers are coated with packaging proteins; in eukaryotic cells the most important of these proteins are ...
have been observed.
Based on DNA analysis, they have a guanine-cytosine content (
GC-content
In molecular biology and genetics, GC-content (or guanine-cytosine content) is the percentage of nitrogenous bases in a DNA or RNA molecule that are either guanine (G) or cytosine (C). This measure indicates the proportion of G and C bases out o ...
) of 55%.
Using molecular diagnostics, ''C. herbarum''
internal transcribed spacer
Internal transcribed spacer (ITS) is the spacer DNA situated between the small-subunit ribosomal RNA (rRNA) and large-subunit rRNA genes in the chromosome or the corresponding transcribed region in the polycistronic rRNA precursor transcript.
I ...
(ITS) sequences have been found to be identical to those of ''Cyphellophora laciniata''.
''
References
{{Taxonbar, from=Q3678954
herbarum
Fungal plant pathogens and diseases
Fungi described in 1815