''Curvularia inaequalis'' is a plant
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 ( ...
that resides in temperate and subtropical environments.
It is commonly found in the
soil
Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Some scientific definitions distinguish ''dirt'' from ''soil'' by restricting the former ...
s of
forage grasses and
grain
A grain is a small, hard, dry fruit ( caryopsis) – with or without an attached hull layer – harvested for human or animal consumption. A grain crop is a grain-producing plant. The two main types of commercial grain crops are cereals and legu ...
s.
The species has been observed in a broad distribution of countries including Turkey, France, Canada, The United States, Japan and India.
This species is
dematiaceous
“Black yeasts”, sometimes also black fungi, dematiaceous fungi, microcolonial fungi or meristematic fungi is a diverse group of slow-growing microfungi which reproduce mostly asexually (fungi imperfecti). Only few genera reproduce by budding ...
and a
hyphomycete.
History and taxonomy
The ''Curvularia'' genus can be identified by its spiral borne phaeophragmospores, which contain both
hyaline
A hyaline substance is one with a glassy appearance. The word is derived from el, ὑάλινος, translit=hyálinos, lit=transparent, and el, ὕαλος, translit=hýalos, lit=crystal, glass, label=none.
Histopathology
Hyaline cartilage is ...
end cells and disproportionately large cells.
They possess
conidia
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 ...
with differing curvature and number of septa.
''C. inaequalis'' was first described in 1907 by ecologist
Cornelius Lott Shear Cornelius Lott Shear (1865–1956) was an American mycologist and plant pathologist. In 1908 he created the American Phytopathological Society
The American Phytopathological Society (APS) is an international scientific organization devoted to t ...
.
The fungus was isolated from diseased New Jersey cranberry pulp
and termed ''Helminthosporium inaequale''.
Later, during
Karl Boedijin's taxonomic organization and grouping of this
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 n ...
, he recognized a similarity between them and ''H. inaequale''.
He recognized a
morphological similarity between its
conidia
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 ...
and those of the
''lunata'' group within ''Curvularia'', and so renamed it ''C. inaequalis''.
Recognition of the three-
septate
In biology, a septum (Latin for ''something that encloses''; plural septa) is a wall, dividing a cavity or structure into smaller ones. A cavity or structure divided in this way may be referred to as septate.
Examples
Human anatomy
* Interatr ...
curved conidia motivated the introduction of the now popularized name.
Growth and morphology
The species' spore producing cells take on a model of
sympodial growth.
Conidia grow through successive apices which end in a terminal porospore.
Growth can be affected by static magnetic fields with field flux densities.
Under these conditions, the number of
conidia
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 ...
are able to increase by a minimum of 68 percent.
''Curvularia inaequalis'' is a filamentous fungus, with 3 to 12 densely packed filaments.
The species is mostly brown in appearance, with pale brown end cells.
Conidia themselves, consist of 3-5 cells with thick cell walls and a larger central cell.
The diameter of the conidia ranges from 10 to 30 micrometers and have a slight leading curvature.
Overall the appearance of the species is described as looking "cottony" with clear branching cells.
The species can be difficult to identify due to its similar appearance to both ''
C.'' and ''
geniculate
The geniculate ganglion (from Latin ''genu'', for "knee") is a collection of pseudounipolar sensory neurons of the facial nerve located in the facial canal of the head. It receives fibers from the facial nerve. It sends fibers that supply th ...
''.
Instead, sequencing of nuclear rRNA
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.
...
regions (ITS) can be done to achieve accurate identification.
Physiology
The optimal growth temperature for the species is 30°C.
It is able to produce a multitude of chemical products with enzymatic properties. One
enzyme
Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different molecule ...
produced is
chloroperoxidase
Chloride peroxidase () is a family of enzymes that catalyzes the chlorination of organic compounds. This enzyme combines the inorganic substrates chloride and hydrogen peroxide to produce the equivalent of Cl+, which replaces a proton in hydrocar ...
, which can catalyze
halogenation
In chemistry, halogenation is a chemical reaction that entails the introduction of one or more halogens into a compound. Halide-containing compounds are pervasive, making this type of transformation important, e.g. in the production of polyme ...
reactions.
Chloroperoxidase secreted from ''C. inaequalis'' contains
vanadium
Vanadium is a chemical element with the symbol V and atomic number 23. It is a hard, silvery-grey, malleable transition metal. The elemental metal is rarely found in nature, but once isolated artificially, the formation of an oxide layer ( pass ...
active site.
The presence of the vanadium substrate
vanadate
In chemistry, a vanadate is an anionic coordination complex of vanadium. Often vanadate refers to oxoanions of vanadium, most of which exist in its highest oxidation state of +5. The complexes and are referred to as hexacyanovanadate(III) and no ...
is essential for the function of chloroperoxidase.
The compound
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, usi ...
however, acts as an
inhibitor
Inhibitor or inhibition may refer to:
In biology
* Enzyme inhibitor, a substance that binds to an enzyme and decreases the enzyme's activity
* Reuptake inhibitor, a substance that increases neurotransmission by blocking the reuptake of a neurotra ...
for both enzyme function and production.
In its active form, the enzyme is able to then produce
hypochlorous acid
Hypochlorous acid (HClO, HOCl, or ClHO) is a weak acid that forms when chlorine dissolves in water, and itself partially dissociates, forming hypochlorite, ClO−. HClO and ClO− are oxidizers, and the primary disinfection agents of chlorine so ...
, a strong
oxidizing agent
An oxidizing agent (also known as an oxidant, oxidizer, electron recipient, or electron acceptor) is a substance in a redox chemical reaction that gains or " accepts"/"receives" an electron from a (called the , , or ). In other words, an oxid ...
.
It has been theorized that ''C. inaequalis'' utilizes chloroperoxidase and hypochlorous acid in combination to penetrate the host's cell wall.
Other significant compounds produced include of
B-galactosidase, and . The species is able to produce large amounts of
β-galactosidase
β-Galactosidase (EC 3.2.1.23, lactase, beta-gal or β-gal; systematic name β-D-galactoside galactohydrolase), is a glycoside hydrolase enzyme that catalyzes hydrolysis of terminal non-reducing β-D-galactose residues in β-D-galactosides.
β- ...
, which can hydrolyze lactose in acid whey.
''C. inaequalis'' also contains 4-hydroxyradianthin and Curvularone A compounds which have been identified as potential anti-tumor agents.
Pathology and toxicology
Plant pathology and toxicology
''Curvularia inaequalis'' is known to cause leaf spot, also known as
Leaf Blight
Blight refers to a specific symptom affecting plants in response to infection by a pathogenic organism.
Description
Blight is a rapid and complete chlorosis, browning, then death of plant tissues such as leaves, branches, twigs, or floral or ...
.
Symptoms of infection by ''C. inaequalis'' include the combination of oval shaped dark brown patches and leaf tip dieback.
The infection slowly spreads causes necrosis until it has covered the entirety of the leaf.
It results in the thinning of grass vegetation such as
Zoysia
''Zoysia'' (;["Zoysia."](_blank)
entry at CollinsDictionary.com. Retrieved 5 September 2021. , -, ...
-,
Bent-,
Bermuda- and
Buffalo- grasses.
Blighting is believed to be caused by two ''C. inaequalis''
mycotoxins
A mycotoxin (from the Greek μύκης , "fungus" and τοξίνη , "toxin") is a toxic secondary metabolite produced by organisms of kingdom Fungi and is capable of causing disease and death in both humans and other animals. The term 'mycotoxin' ...
,
Pyrenocine
Pyrenocines are 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 ...
s and .
Pyrenocines A is the more potent of the two, stunting growth and causing necrosis in vegetation.
Both cause leaf tip die back in turf grass and leaf leakage of
electrolytes in Bermuda grass.
Human pathology
''Curvularia inaequalis'' is typically a rare human pathogen.
There are however, recorded medical cases that mention infection by the species. One such case is of an
Eosinophilic
Eosinophilic (Greek suffix -phil-, meaning ''loves eosin'') is the staining of tissues, cells, or organelles after they have been washed with eosin, a dye.
Eosin is an acidic dye for staining cell cytoplasm, collagen, and muscle fibers. ''E ...
fungal
rhinosinusitis
Rhinosinusitis is a simultaneous infection of the nasal mucosa ( rhinitis) and an infection of the mucosa of the paranasal sinuses ( sinusitis). A distinction is made between acute rhinosinusitis and chronic rhinosinusitis.
Background
Because si ...
in an immunocompromised male.
Endoscopic
An endoscopy is a procedure used in medicine to look inside the body. The endoscopy procedure uses an endoscope to examine the interior of a hollow organ or cavity of the body. Unlike many other medical imaging techniques, endoscopes are inser ...
sinus surgery was required to remove a large
polyposis.
''C. inaequalis'' was found to have grown favorably in the eosinophilic mucus.
Oral
itraconazole
Itraconazole, sometimes abbreviated ITZ, is an antifungal medication used to treat a number of fungal infections. This includes aspergillosis, blastomycosis, coccidioidomycosis, histoplasmosis, and paracoccidioidomycosis. It may be given by mout ...
and other
corticosteroids
Corticosteroids are a class of steroid hormones that are produced in the adrenal cortex of vertebrates, as well as the synthetic analogues of these hormones. Two main classes of corticosteroids, glucocorticoids and mineralocorticoids, are in ...
successfully were administered to prevent reinfection.
Another case of ''C. inaequalis'' causing disease includes
peritonitis
Peritonitis is inflammation of the localized or generalized peritoneum, the lining of the inner wall of the abdomen and cover of the abdominal organs. Symptoms may include severe pain, swelling of the abdomen, fever, or weight loss. One part or ...
in an elderly patient.
It is suggested that contraction of the fungus occurs due to contact with soils.
Furthermore, a case of recorded aerosolized ''C. inaequalis'' in one Canadian home supports airborne movement of spores as an important mode of transfer.
While many cases of infection due to soil contact with the genus ''Curvularia'', connection with the specific species has not yet been confirmed.
Further studies are required to determine its human pathogen potential.
References
{{Taxonbar , from = Q10463928
Pleosporaceae
Fungi described in 1907