Stachybotrys chartarum

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1. Classification

a. Higher order taxa

Eukaryota (Kingdom), Fungi (Domain), Ascomycota (Phylum), Sordariomycetes (Class), Hypocreales (Order), Stachybotryaceae (Family), Stachybotrys (Genus) [1]

b. Species

Stachybotrys chartarum

2. Description and significance

Stachybotrys chartarum, more commonly known as black mold, is a fungus prevalent in various environments, ranging from damp indoor spaces to food sources that both humans and livestock ingest [2]. Although its morphology and taxonomy were initially described in the 1830s by August Carl Joseph Corda, subsequent studies throughout the 20th century have raised questions about its size, ratio of conidia and phialides, and delineation from other species [3]. S. chartarum produces mycotoxins associated with detrimental health effects in humans and animals. It is the proposed pathogen for localized incidences of pulmonary hemorrhage in infants and other severe pulmonary conditions [4]. Current research efforts are still trying to discern the scope of its biological capabilities regarding indoor air quality and human health effects [3].

3. Genome structure

The complete genome of S.chartarum strain 51-11 spans approximately 40Mb [5]. With 9 sequence runs performed by Illumina Sequencing, there were approximately 736 million bases total, with about 2,600 bases per read5. The GC content for the S.chartarum genome is 53% [6]. Furthermore, based on the genes essential for satratoxin and atranone production (satratoxin cluster, SC1-3, sat or atranone cluster, AC1, atr), S. chartarum can be categorized into three groups: the S-type possessing all sat- but no atr-genes, the A-type lacking the sat- but harboring all atr-genes, and the H-type having only certain sat- and all atr-genes [6]. Genotype H is believed to represent the most ancient form of this fungus, with genotype S emerging from a loss of AC1 and the simultaneous acquisition of SC2 [6]. The development from genotype H to genotype A is believed to be accompanied by the loss of SC1 and SC3 [6].

4. Cell structure

S.chartarum, a gram-negative fungus, possesses a rigid cell wall primarily composed of chitin [7,8]. When cultivated in media, it exhibits a dark color, giving rise to its common name. This fungus forms raised, circular colonies and consists of nonmotile bodies known as thalli, composed of apically elongating walled filaments (hyphae), which constitute the primary growth form of S. chartarum [9]. This structure can also branch out and become intertwined to form complex structures (e.g. rhizomorphs) [9]. Additionally, S. chartarum contains cellular cross walls called septa [8]. In S. chartarum, sporulation is triggered when food becomes depleted, as well as during its reproduction cycle [9].

5. Metabolic processes

S. chartarum exists in two chemotypes that produce different mycotoxins. Chemotype A produces atranones, while chemotype S produces macrocyclic trichothecenes [10]. The mutually exclusive production of either satratoxins or atranones defines the chemotypes A and S [6]. Macrocyclic trichothecenes include satratoxins, which are suspected to cause harm to humans and other animals [10]. Mycotoxin production and sporulation in S. chartarum are intertwined processes suspected to be regulated by G-protein signaling pathways, which also control developmental processes and stress responses [10]. The presence of neighboring colonies in strains of S. chartarum also stimulates mycotoxin production and sporulation [10]. S. chartarum is a chemoorganotroph which means that it obtains energy from the oxidation of organic compounds [11]. Nitrogen is a crucial element for the metabolism of S. chartarum; as nitrogen availability increases, it manufactures a higher mycotoxin production [10]. Common home building materials such as gypsum board, wood board, plywood, and cellulose insulation are all susceptible to S. chartarum decomposition under moist conditions [12]. S. chartarum produces an extracellular enzyme, cellulase, to digest and break down these home-building materials, which primarily consist of cellulose [13].

6. Ecology

S. chartarum is found around the world, usually in areas high in cellulose [14]. It grows optimally in moist environments with a minimum water activity (aw) of at least 0.95 [15]. This poses a problem for flooded or damp homes, where S. chartarum can thrive. As moisture and aw decrease, so do the activity and growth of S. chartarum [15]. However, sporulation isn’t negatively affected when moisture decreases to an aw of 0.95. Thus, even when flooded homes are dried out, there is still a risk of spore contamination [15]. The optimal temperature for growth of this fungus is 30°C, although sporulation can still occur at temperatures reaching 15-20°C [15]. As the temperature deviates from 30°C, the total radial growth and rate of growth decreases [16]. Because of S. chartarum’s ability to decompose cellulose, buildings with cellulose insulation and wood supports are prime candidates for fungal growth [17]. S. chartarum generally does not compete well with other fungi and is rarely found outside [17]. However, this fungus has been found and isolated from soybean roots [18].

7. Pathology

How does this organism cause disease? Human, animal, plant hosts? Virulence factors, as well as patient symptoms.

9. Current Research

Include information about how this microbe (or related microbes) are currently being studied and for what purpose

9. References

It is required that you add at least five primary research articles (in same format as the sample reference below) that corresponds to the info that you added to this page. [Sample reference] Faller, A., and Schleifer, K. "Modified Oxidase and Benzidine Tests for Separation of Staphylococci from Micrococci". Journal of Clinical Microbiology. 1981. Volume 13. p. 1031-1035.