Acremonium strictum | |
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Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Fungi |
Division: | Ascomycota |
Class: | Sordariomycetes |
Order: | Hypocreales |
Family: | Hypocreaceae |
Genus: | Acremonium |
Species: | A. strictum |
Binomial name | |
Acremonium strictum W.Gams (1971) | |
Synonyms | |
Acremonium strictum is an environmentally widespread saprotroph species found in soil, plant debris, and rotting mushrooms. [1] Isolates have been collected in North and Central America, Asia, Europe and Egypt. [2] A. strictum is an agent of hyalohyphomycosis and has been identified as an increasingly frequent human pathogen in immunosuppressed individuals, causing localized, disseminated and invasive infections. [2] [3] [4] Although extremely rare, A. strictum can infect immunocompetent individuals, as well as neonates. [3] [4] Due to the growing number of infections caused by A. strictum in the past few years, the need for new medical techniques in the identification of the fungus as well as for the treatment of human infections has risen considerably. [5]
Acremonium strictum has been shown to be involved in some myoparasitic relationships, as well as a wide range of plant endophytic and parasitic relationships, [6] [7] [8] [9] and further studies are required to determine A. strictum's use as a biological control agent and role as a parasite that reduces crop yields. A. strictum exhibits metabolism of many products that imply future agricultural and pharmaceutical significance. [10] [11]
The genus Acremonium is a large polyphyletic genus of approximately 150 species, many of which are derived from a closely related families in the Sordariomycetes. [12] The genus includes many slow growing, simply structured, anamorphic filamentous fungi, [3] [5] [12] typically encountered in wet, cellulose-based building materials suffering form chronic wet conditions. [13] Characteristic morphology in this genus is septate hyphae giving rise to thin, tapered aculeate phialides that are usually unicellular, or weakly branched conidiophores. [1] [5] [12] Human infections, though rare, usually occur in severely immunodeficient individuals. [2] A. strictum is mostly known to be involved with myparasitic relationships, as well as being a plant parasite and endophyte. [6] [14] [15]
Acremonium strictum grows readily at 30 °C on glucose peptone agar, showing mycelium of approximately 50mm in size in 7 days. Colonies are flat, with smooth, wet, velvety or floccose texture, sometimes resembling thin cottony mounds. [16] The colour of mycelia ranges widely from light pink to orange, and sometimes yellow, white or green. [5] [16] A. strictum filaments are sometimes bound together into ropes several cells in diameter. [1] Conidia grow as wet clusters or dry chains, [1] and grains produced are white to pale-yellow, soft and variable in shape. [1] Subcultures of the fungus can also be grow within seven days into smooth, moist, pink mycelia that resemble thin cotton. [5] [17]
Under the microscope at 30 °C, A. strictum shows long slender phialides, and conidia are cylindrical or ellipsoidal, formed in slimy bundles at the tips of the phialides. Lower microscopy shows pin-head spore ball formation. [16]
Species of Acremonium are morphologically very similar, making identification difficult. Shown in the image is a microscopic image of A. falciforme, an example showing the morphological similarities to A. strictum. Cases involving different species of Acremonium are often reported as simply as an Acremonium species, which reduces the amount of accurate information on the clinical presentation of A. strictum. [5] Isolates of phylogenetically remote species of Acremonium show considerable convergence. [12] As a human pathogen, diagnosis is made in isolation and identification of the fungus from granules in tissue and the presence of hyphae in microscopic examination of cutaneous biopsy and discharge. [1] [3]
Genera that are morphologically similar to Acremonium include Fusarium , Phaeoacremonium , Verticillium , Phialemonium , and Lecanicillium . [5]
Identification of A. strictum isolates has shown that this fungus is phenotypically diverse and may vary genetically. [17] Due to phylogenetic ambiguities, an unknown proportion of the literature on A. strictum is based on studies of Acremonium sclerotigenum. [12] The fungus can generally be successfully identified by the nuclear ITS region sequence analysis. [5] [18] Analysis of the genes for ribosomal large subunit (LSU) and whole small subunit (SSU) also help to elucidate phylogenetic relationships, since these genes are more conserved and less subject to evolutionary changes. [12] The species A. strictum is separated into three genogroups. Genogroup I is represented by type strain CBS 346.70, genogroup II by UW836 and genogroup III by UWFP940. These genogroups were determined based on GenBank entries for A. strictum.
Human infections of Acremonium strictum are very rare, and usually develop after traumatic inoculation of the fungus. [5] Hyalophomycosis may occur in immunodeficient individuals, presented in the infected tissue by hyaline or colourless hyphae. [1] [4] Peritonitis and pleuritis have resulted from A. strictum infections, [19] [20] but cutaneous and subcutaneous infections of A. strictum are rarely reported.
Many environmental factors such as the density of fungi in soil, rainfall, temperature, humidity and types of vegetation in close contact are relevant in determining the likelihood of acquiring hyalohypjomycosis infection by A. strictum. [3] Frequent exposure to contaminated water along with high temperature and humid environments increases the risk of infection. [3]
Clinical presentation of an infection is ill-defined, but most individuals may present a skin rash and flu like symptoms, such as elevated body temperature and fatigue. [1] [3] In more severe infections, such as in immunodeficient individuals, peritonitis and pleuritis, and may lead to multi-organ failure. [19] [20] In the case of invasive infections, surgical intervention may be required to remove fungal mass from body tissues. [4] Due to limited, ill-defined cases and the variance in clinical presentation and species identification, no optimal treatments are available. [2] A. strictum and other Acremonium species are generally resistant to most antifungals, but antifungal susceptibility testing is recommended to select the most appropriate treatment for the strain of A. strictum that is the infection agent. [3] Amphotericin B therapy coupled with ketoconazole is usually recommended as the best available treatment. [2] [3]
It has been shown that seedlings infected with A. strictum have high mortality rates. It would be agriculturally significant to identify biological control agents for this fungus. Aerial parts of Cymbopogon schoenanthus , Hyptis spicigera , Lantana camara and Ocimum americanum were collected and air-dried for four days. After drying the plants, essential oils were extracted from the materials. A variety of seeds inoculated with fungi, some cohorts with A. strictum. The oils were applied to the infected seeds. After allowing seedlings to develop, it was found that the oils in combination inhibited A. strictum mycelial growth significantly.[ citation needed ]
Acremonium strictum is generally known as a mycoparasite, as shown in its antagonistic relationship with Helminthosporium solani . H. solani is a potato (Solanum tuberosum) associated fungus, that has caused extreme and widespread losses in all market classes of potatoes since emerging in the United States. Commonly referred to as silver scurf, H. solani causes blemishes that decreases the quality of the crop, making it unfit for marketing. In more severe cases, H. solani causes weight loss in potatoes and creates lesions in the periderm, creating entry points for other tuber pathogens. In pure cultures of H. solani, isolates show white sectoring and rings, differential coloration and reduced sporulation in culture. Upon infection of A. strictum, cultures of H. solani were uniformly black, without white sectors or rings. A. strictum was able to significantly reduce sporulation of H. solani by 30%, spore germination by 20%, and mycelial growth 8% in culture. This evidence suggests that A. strictum may be used as a biological control agent against H. solani, which would greatly increase potato crop yields. [6]
Acremonium strictum is pathogenic to many monocotyledonous and dicotyledonous crops, causing leaf desiccation on one side of the midrib of these plants, plant wilt and abnormal, discoloured vasculature of the stalk near the soil line. Vasculature of the plant forms orange, red and brown bundles, usually resulting in death. Infection of A. strictum is systemic, and the fungus can be isolated from all tissues of the plant. Isolates have been found in plant seeds, which is probably the route of dissemination of the fungus. Crops affected by A. strictum include Acacia , Alnus, Ficus , Glycine, Gossypium , Triticum and Zea . Because of its ubiquitous presence in soils, A. strictum negatively impacts many agricultural plants, although more research is needed to investigate the parasitic interactions and develop strategies for its biological control. [14]
Meloidogyne incognita is a polyphagous nematode that severely damages tomato crops by causing lesions in the roots by using a stylet, which allows other soil-dwelling fungal parasites to infect the host plant and cause complex disease interactions. A. strictum is reported to be a nematode egg parasite, as the eggs of M. incognita infested plants were found to be empty under A. strictum treatment. This treatment of A. strictum coupled with Trichoderma harzianum was found to be a very promising combination in the control of M. incognita in tomato plants. [15]
It demonstrates a complicated relationship with strawberry host Fragaria ananassa, [7] in which the fungus may cause lesions and small necrotic, light-brown spots in leaves and petioles which increase as the disease progresses, adversely affecting strawberry crop. [21] Eventually the necrotic regions expand and cause the plant to wilt, but crown rot is not observed at any stage of the infection. [21] Although it appears to have a parasitic relationship with Fragaria ananassa, it also produces an elicitor protein, AsES, which provides systemic protection against anthracnose disease in strawberry host Fragaria ananassa, which shows a symbiotic relationship between the strawberry plant and Acremonium strictum. [7]
Atractylodes lancea is a medicinal herb that grows in central China. A. strictum acts as a fungal endophyte and interacts with A. lancea in drought conditions and confers tolerance in moderate drought. Under mild drought conditions, A. strictum enhanced leaf soluble sugars, proteins, proline and antioxidant enzyme activity, which decreased the degree of plasmalemma oxidation. This increased A. lancea abscisic acid level and root:shoot ratio. While A. strictum may alleviate the effects of a mild to moderate drought, benefits of this endophytic relationship are constrained by drought degree, as there were no significant effects of A. strictum on A. lancea during periods of regular watering or severe drought. [8]
In Maclura cochinchinensis , Acremonium strictum acts as an endophytic fungi that infects primarily the leaves of the plant. In this relationship, A. strictum was found to provide and mediate a protective response against herbivorous insects. [9]
Acremostrictin can be isolated from certain strains of A. strictum and is characterized as a highly oxygenated, tricyclic lactone metabolite. [22] This compound exhibits weak antibacterial properties against the bacterium Micrococcus luteus , Salmonella typhimurium and Proteus vulgaris . However, it had no effect on Bacillus subtilis , Staphylococcus aureus and Escherichia coli . [22] Acremostrictin has been shown to have concentration-dependent antioxidant activity, which conferred protection against oxidative stress induced cell death. Acremostrictin was shown to inhibit H2O2-induced death of human keratinocyte HaCaT cells. When extracted and isolated by filtration, acremostrictin presents as a colorless crystal solid. [22]
AsES (A. strictum elicitor subtilisin; R4IR27 ) protein is an extracellular elicitor protein produced by A. strictum that provides complete systemic protection against anthracnose, cause by the fungal species Colletotrichum , in the natural host Fragaria ananassa as well as the non-natural host Arabidopsis thaliana . Anthracnose can affect all plant tissues, and appears as irregular and black leaf spot, flower blight, and fruit and crown rot, which results in serious losses in plant and fruit production. AsES has proteolytic activity that appears to elicit an immune response in these species that results in the accumulation of reactive oxygen species and the expression of defence related genes like PR1 and Chi2-1. Because it has been shown to provide the same systemic protection in non-natural hosts, this natural metabolite of A. strictum may be considered as a possible strategy for controlling anthracnose disease in plants. [7]
Acremonium strictum produces some types of cephalosporins a group of antibiotics.
Biogenic Mn oxides (BMOs) are naturally occurring Mn oxides that have the ability to oxidize various redox-sensitive elements. A. strictum is a Mn(II)-oxidizing fungus that forms BMOs through the action of Mn(II) oxidase. In the presence of BMOs in buffer solutions with no additional nutrients, A. strictum is capable of sequestering high Mn(II) concentrations for at least 8 days, in which the amount of dissolved Mn(II) decreases rapidly in several hours and is converted to oxidized Mn(II). Deaeration of the buffer solution with N2 gas purging suppressed Mn(II) conversion, but this suppression is easily rescued by aeration, implying that dissolved oxygen is required for the Mn(II) sequestration and oxidation process. Adding NaN3, a toxic substance, also significantly reduces the sequestration rates of the fungal BMOs. Heat treatments revealed that temperatures below 85 °C do not alter the conformation of the Mn(II) oxidase in the BMOs. Freezing the fungal BMOs at −80 °C for 4 weeks did not affect the Mn(II) ability, and the reducible Mn was still dominated in solution. This makes fungal BMOs an effective Mn(II) sequestering material if needed. For example, it can be used for the continuous removal of Mn(II) from Mn(II) contaminated water without the need for any additives other than dissolved oxygen. The product is an oxide phase Mn(II) that would provide additional affinity for other toxic elements and thus prove as an effective method of water cleansing. Enzymatically active fungal BMOs can be harvested under specific cultivation conditions and remain active even under circumstances that would be unfavourable for fungal growth. [11]
Fermentation of ginsenoside Rb(1) with A. strictum yields three new compounds — 12β-hydroxydammar-3-one-20 (S)-O-β-D-glucopyranoside, 12β, 25-dihydroxydammar-(E)-20(22)-ene-3-O-β-D -glucopyranosyl-(1→2)-β-D -glucopyranoside, and 12β, 20 (R), 25-trihydroxydammar-3-O-β-D -glucopyranosyl-(1→2)-β-D -glucopyranoside — as well as five known compounds — ginsenoside Rd, gypenoside XVII, ginsenoside Rg, ginsenoside F, and compound K. Many of these compounds are metabolites of ginsenoside Rb(1) in mammals, suggesting that fermentation of ginsenoside Rb(1) in A. strictum may be similar to mammalian metabolism and may be a useful agent for generating specific metabolites or related ginsenoside analogs, which can be later isolated for structural elucidation and use in pharmaceutical research. [10]
Eumycetoma, also known as Madura foot, is a persistent fungal infection of the skin and the tissues just under the skin, affecting most commonly the feet, although it can occur in hands and other body parts. It starts as a painless wet nodule, which may be present for years before ulceration, swelling, grainy discharge and weeping from sinuses and fistulae, followed by bone deformity.
Fungal keratitis is a fungal infection of the cornea, which can lead to blindness. It generally presents with a red, painful eye and blurred vision. There is also increased sensitivity to light, and excessive tears or discharge.
Sporothrix schenckii, a fungus that can be found worldwide in the environment, is named for medical student Benjamin Schenck, who in 1896 was the first to isolate it from a human specimen. The species is present in soil as well as in and on living and decomposing plant material such as peat moss. It can infect humans as well as animals and is the causative agent of sporotrichosis, commonly known as "rose handler's disease." The most common route of infection is the introduction of spores to the body through a cut or puncture wound in the skin. Infection commonly occurs in otherwise healthy individuals but is rarely life-threatening and can be treated with antifungals. In the environment it is found growing as filamentous hyphae. In host tissue it is found as a yeast. The transition between the hyphal and yeast forms is temperature dependent making S. schenckii a thermally dimorphic fungus.
Epichloë is a genus of ascomycete fungi forming an endophytic symbiosis with grasses. Grass choke disease is a symptom in grasses induced by some Epichloë species, which form spore-bearing mats (stromata) on tillers and suppress the development of their host plant's inflorescence. For most of their life cycle however, Epichloë grow in the intercellular space of stems, leaves, inflorescences, and seeds of the grass plant without incurring symptoms of disease. In fact, they provide several benefits to their host, including the production of different herbivore-deterring alkaloids, increased stress resistance, and growth promotion.
Acremonium is a genus of fungi in the family Hypocreaceae. It used to be known as Cephalosporium.
Cochliobolus lunatus is a fungal plant pathogen that can cause disease in humans and other animals. The anamorph of this fungus is known as Curvularia lunata, while C. lunatus denotes the teleomorph or sexual stage. They are, however, the same biological entity. C. lunatus is the most commonly reported species in clinical cases of reported Cochliobolus infection.
Setosphaeria rostrata is a heat tolerant fungus with an asexual reproductive form (anamorph) known as Exserohilum rostratum. This fungus is a common plant pathogen, causing leaf spots as well as crown rot and root rot in grasses. It is also found in soils and on textiles in subtropical and tropical regions. Exserohilum rostratum is one of the 35 Exserohilum species implicated uncommonly as opportunistic pathogens of humans where it is an etiologic agent of sinusitis, keratitis, skin lesions and an often fatal meningoencephalitis. Infections caused by this species are most often seen in regions with hot climates like Israel, India and the southern USA.
Microdochium panattonianum is a fungal plant pathogen. This pathogen causes anthracnose of lettuce, a disease which produces necrotic lesions in cultivated lettuce. In extended periods of wet weather, M. panattonianum can cause significant crop-losses. The impact of this pathogen is exacerbated by farming lettuce without crop rotation, and by planting of susceptible lettuce varieties, such as Romaine lettuce.
Fusarium solani is a species complex of at least 26 closely related filamentous fungi in the division Ascomycota, family Nectriaceae. It is the anamorph of Nectria haematococca. It is a common soil fungus and colonist of plant materials. Fusarium solani is implicated in plant diseases as well as in serious human diseases such as fungal keratitis.
Helminthosporium solani is a fungal plant pathogen responsible for the plant disease known as silver scurf. Silver scurf is a blemish disease, meaning the effect it has on tubers is mostly cosmetic and affects "fresh market, processing and seed tuber potatoes." There are some reports of it affecting development, meaning growth and tuber yield. This is caused by light brown lesions, which in turn change the permeability of tuber skin and then it causes tuber shrinkage and water loss, which finally causes weight loss. The disease has become economically important because silver scurf affected potatoes for processing and direct consumption have been rejected by the industry. The disease cycle can be divided into two stages: field and storage. It is mainly a seed borne disease and the primary source of inoculum is mainly infected potato seed tubers. Symptoms develop and worsen in storage because the conditions are conducive to sporulation. The ideal conditions for the spread of this disease are high temperatures and high humidity. There are also many cultural practices that favor spread and development. There are multiple ways to help control the disease.
Exophiala jeanselmei is a saprotrophic fungus in the family Herpotrichiellaceae. Four varieties have been discovered: Exophiala jeanselmei var. heteromorpha, E. jeanselmei var. lecanii-corni, E. jeanselmei var. jeanselmei, and E. jeanselmei var. castellanii. Other species in the genus Exophiala such as E. dermatitidis and E. spinifera have been reported to have similar annellidic conidiogenesis and may therefore be difficult to differentiate.
Piedraia hortae is a superficial fungus that exists in the soils of tropical and subtropical environments and affects both sexes of all ages. The fungus grows very slowly, forming dark hyphae, which contain chlamydoconidia cells and black colonies when grown on agar. Piedraia hortae is a dermatophyte and causes a superficial fungal infection known as black piedra, which causes the formation of black nodules on the hair shaft and leads to progressive weakening of the hair. The infection usually infects hairs on the scalp and beard, but other varieties tend to grow on pubic hairs. The infection is usually treated with cutting or shaving of the hair and followed by the application of anti-fungal and topical agents. The fungus is used for cosmetic purposes to darken hair in some societies as a symbol of attractiveness.
Sagenomella is a genus of filamentous Ascomycota fungus that has reported to cause systemic illness in animals. The genus was circumscribed by Walter Gams in 1978.
Apophysomyces variabilis is an emerging fungal pathogen that can cause serious and sometimes fatal infection in humans. This fungus is a soil-dwelling saprobe with tropical to subtropical distribution. It is a zygomycete that causes mucormycosis, an infection in humans brought about by fungi in the order Mucorales. Infectious cases have been reported globally in locations including the Americas, Southeast Asia, India, and Australia. Apophysomyces variabilis infections are not transmissible from person to person.
Coniochaeta hoffmannii, also known as Lecythophora hoffmannii, is an ascomycete fungus that grows commonly in soil. It has also been categorized as a soft-rot fungus capable of bringing the surface layer of timber into a state of decay, even when safeguarded with preservatives. Additionally, it has pathogenic properties, although it causes serious infection only in rare cases. A plant pathogen lacking a known sexual state, C. hoffmannii has been classified as a "dematiaceous fungus" despite its contradictory lack of pigmentation; both in vivo and in vitro, there is no correlation between its appearance and its classification.
Scedosporiosis is the general name for any mycosis – i.e., fungal infection – caused by a fungus from the genus Scedosporium. Current population-based studies suggest Scedosporium prolificans and Scedosporium apiospermum to be among the most common infecting agents from the genus, although infections caused by other members thereof are not unheard of. The latter is an asexual form (anamorph) of another fungus, Pseudallescheria boydii. The former is a "black yeast", currently not characterized as well, although both of them have been described as saprophytes.
Neoscytalidium dimidiatum was first described in 1933 as Hendersonula toruloidea from diseased orchard trees in Egypt. Decades later, it was determined to be a causative agent of human dermatomycosis-like infections and foot infections predominantly in tropical areas; however the fungus is considered to be widespread. A newer name, Scytalidium dimidiatum, was applied to a synanamorph of Nattrassia mangiferae, otherwise known as Neofusicoccum mangiferae. Substantial confusion has arisen in the literature on this fungus resulting from the use of multiple different names including Torula dimidiata, Fusicoccum dimidiatum, Scytalidium dimidiatum, and Hendersonula toruloidea. Additionally, Scytalidium lignicola and Scytalidium lignicolum are often considered earlier names of N. dimidiatum.
Sagenomella keratitidis is a hyphomycete discovered as its own species in 2008 by Sung-Yaon Hsieh et al. at the Institute of Plant and Microbial Biology and the National Taiwan University Hospital.
Sarocladium kiliense is a saprobic fungus that is occasionally encountered as a opportunistic pathogen of humans, particularly immunocompromised and individuals. The fungus is frequently found in soil and has been linked with skin and systemic infections. This species is also known to cause disease in the green alga, Cladophora glomerata as well as various fruit and vegetable crops grown in warmer climates.
Myriodontium keratinophilum is a fungus widespread in nature, most abundantly found in keratin-rich environments such as feathers, nails and hair. Despite its ability to colonize keratinous surfaces of human body, the species has been known to be non-pathogenic in man and is phylogentically distant to other human pathogenic species, such as anthropophilic dermatophytes. However, its occasional isolation from clinical specimens along with its keratinolytic properties suggest the possibility it may contribute to disease.