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 Add this item to the list   Sporotrichum pruinosum Gilman & Abbott
   
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Description type:Culture description 
Description:Sporotrichum pruinosum Gilman & Abbott
Teleomorph: Phanerochaete chrysosporium Burdsall
Growth on MEA and ChA: 70 mm radius in 10-14 days. Cardinal temperatures: minimum 7¦ C, optimum 36-40°C, maximum 46-49°C. Advancing zone appressed, even, hyphae distant. Colony appressed at the margin, becoming locally farinaceous to mealy-floccose and finally nearly completely farinaceous, white to cream-coloured, sometimes with a faint to distinct greyish or pinkish hue; hyaline spots without aerial mycelium may be present in the colony. After 6 weeks colonies becoming felty. Reverse paler. Reaction with a-naphthol negative or weak, forming an open purplish ring after 1-3 days. Reaction with pcresol negative. Odour insignificant.
Marginal hyphae hyaline, thin-walled, 3-7.5(-8) µm wide, with few septa, lacking clamps. Cells multinucleate. Branching generally inequivalent with much wider parent hyphae. Crystals absent. Aerial hyphae hyaline, 2.5-5(-8) µm wide, thin- to thick- walled, septate, without clamps, often covered with crystalline or granular material. Branching generally equivalent. Conidiophores simple or typically branched. Branching racemose, each branch forming a terminal blastoconidium. Blastoconidia from branched conidiophores hyaline, subglobose to ellipsoidal or ovoidal, (5-)6-10(-11.5) x (4-)5-8.5(-10) µm. Blastoconidia from unbranched conidiophores ellipsoidal to ovoid pyriform or nearly cylindrical, 5-8(-10.5) x (3-)3.5-4.5(- 5.5) µm. All blastoconidia broadly attached and becoming thickwalled. Chlamydospores terminal or intercalary, hyaline, (sub)globose to broadly ellipsoidal or more rarely pyriform, 11- 60 µm diam or 11-18 x 7.5-15 µm, with granular contents and thick walls (up to 4.5 µm). Arthroconidia hyaline, cylindrical or rather irregular, often with granular contents, thin-walled, but sometimes becoming slightly thick-walled and more ellipsoidal. Crystals often present, hyaline, bipyramidal or prismatic. Submerged hyphae hyaline, 2.5-8 µm wide, thin- to thick-walled (up to 1.5 µm), often irregular in outline or with swellings. Ellipsoidal intercalary chlamydospores sometimes present.
Nuclear behaviour: young cells of radiating mycelium multinucleate, those of aerial mycelium multinucleate, conidia with 2-8 nuclei.
Species code (Stalpers, 1978): (1), (5), (6), (11), 13, 14, 18, 19, (25), 30, (31), 37, 48, 50, 52, 53, 54, (55), 57, 80, 82, 83, 84, 85, 86, 87, (88), (89), (90), 96, 98.
Species code (Nobles, 1965): 1, 6, (7), 14, (25), 26, 33, 34, 35, 36, 40, 41-42, (48), 54, 55.

The teleomorph of S. pruinosum, Phanerochaete chrysosporium Burdsall (Fig. 9) was obtained in several strains on a Walseth medium (Gold and Cheng, 1979). It has been adequately described by Burdsall and Eslyn (1974) and illustrated by Eriksson et al. (1978) and need not be described here. CBS 316.75, however, displayed a remarkable and not earlier reported feature: the number of the sterigmata varied from 2-8, the majority being 5-6 (Fig. 9d-e). The distance from the sterigmata to the axis of the basidium and to each other is not always similar, which makes such basidia look like a Spiniger anamorph (Fig. 9e). The basidiospores, however, are asymmetrical and forcibly discharged. Sometimes they do not mature simultaneously, but in two groups.
Among the species of Sporotrichum, S. pruinosum is the most variable. Macroscopically the colonies are more or less farinaceous, but they vary from a completely white mat to a transparent colony with some local mealy white spots. CBS 129.27 and CBS 363.65 deviate somewhat; colonies of these strains tend to be short woolly, due to the relatively low production of conidia.
Blastoconidial size and shape also vary considerably, as summarized in table 2. Typical isolates have globose to broadly ellipsoidal blastoconidia, few solitary blastoconidia and few arthroconidia. After prolonged maintenance in culture some changes may occur; the total number of conidia as well as the number of conidia per conidiophore may decrease and that of arthroconidia, solitary blastoconidia and chlamydospores increases. Atypical strains, such as CBS 129.27 and CBS 363.65, only rarely display branched conidiophores.
In the original description, Gilman and Abbott (1927) described the mat as "dusty" or "powdery" and the conidiophores as "freely branched". The conidial shape was originally described as oval or lemon-shaped and the figure (reproduced here as Fig. 6f) showed a rather typical conidiophore. Nowadays the type strain (CBS 129.27) is atypical as is the similar CBS 363.65. The latter strain is an authentic strain of Emmonsia ciferrina, a species for which the original description agrees with the above description of S. pruinosum. The degeneration may have been caused or hastened by a minute bacterium, which was not detectable in malt-peptone solution or bright-field microscopy (there is always fine encrusting material present), but was apparent when studied with fluorescence techniques. It was not present in the other strains studied. The isolate was purified with antibiotics, but did not revert to its original condition.

The synonymy of S. pruinosum and S. pulverulentum was recently debated. Burdsall and Eslyn (1974) considered the two species synonyms, whilst Stalpers (1978) distinguished them on the basis of conidium and chlamydospore size. The present study which included the examination of additional strains, showed the variability to be greater than I (1978) had realized, thus Burdsall and Eslyn's concept is accepted here. Meanwhile Burdsall (1981) in a study on the type strains of S. pruinosum and S. pulverulentum, concluded that they were not conspecific. His main argument was that S. pruinosum was not strongly ligninolytic since it did not degrade 14C-labelled synthetic lignin-like compounds, while S. pulverulentum and other strains of Phanerochaete chrysosporium did. Whatever may be the sensitivity of this method, some literature data indicate a variable pattern of lignin degradation in Ph. chrysosporium. Rosenberg (1980) found, that his strain ME 446 did not degrade lignin in inoculated diffusion cultures, contrary to other Ph. chrysosporium isolates. It did, however, degrade lignin on agar plates. This strain was also studied by Burdsall, who considered it a typical Ph. chrysosporium. The present results of the a-naphthol tests (table 3) also indicate that this character is not stable in S. pruinosum and should not be used for species delimitation.
Besides the inability to degrade lignin, Burdsall listed four morphological characters (considered by him as rather minor) to distinguish S. pruinosum from S. pulverulentum. These are listed below with some comments.
1. The hyphae of S. pruinosum become only slightly thick-walled, while those of S. pulverulentum have walls up to 4 µm thick.
Although the number of thick-walled hyphae and the degree of wall thickness are higher in S. pulverulentum, S. pruinosum also forms such structures (Fig. 6k), especially on ChA.
2. The hyphae of S. pulverulentum are irregularly swollen and the swellings often become large, elongate, intercalary chlamydospores. In S. pruinosum these swellings and chlamydospores are less frequent and usually smaller and ellipsoidal.
Within S. pulverulentum sensu Burdsall the number of swellings and the shape and size of the chlamydospores are very variable. In some strains more or less globose, thick-walled chlamydospores up to 60 µm diam occur, while in others they hardly surpass 15 µm diam. In CBS 129.27 globose chlamydospores were found up to 22 ym diam. Burdsall's drawings suggest that he looked at structures transitional between chlamydospores and arthroconidia which have become thick-walled. Such structures can be found in all isolates.
3. S. pruinosum has subglobose to nearly pyriform arthroconidia, while those of S. pulverulentum are sphaeropedunculate.
Burdsall was probably referring to blastoconidia rather than arthroconidia and confused the terms, as sphaeropedunculate blastoconidia are present in the type strain of S. pruinosum, but not or only rarely so in S. pulverulentum; this is also clear from his drawings. As mentioned before, the type strain of S. pruinosum only rarely produces branched conidiophores. The conidia from these conidiophores, and terminal conidia from unbranched conidiogenous hyphae, are often sphaeropedunculate, as the septa are generally formed somewhat below the swelling. In the original description neither sphaeropedunculate conidia nor arthroconidia are mentioned.
4. S. pruinosum has swollen hyphal ends, up to 10-15 µm diam, which are absent in S. pulverulentum.
This seems to be related to the foregoing character. A conidiophore of CBS 129.27 often produces only one conidium, which may be somewhat larger than average. It seems, that sometimes no septum is formed close to the swelling and that no secession takes place, resulting in capitate hyphae. They are very rarely found in typical strains.
Burdsall obtained subcultures of the type strain of S. pruinosum from four different culture collections and found them similar. By doing so, he suggested that degeneration of this strain is unlikely, because that would have implied parallel degeneration in four different collections, where the strains have been kept under different conditions. The history of their maintenance in those collections is shown in Diagram l. It is clear, that from 1927 to 1949 there has been no separate development, as the original ATCC strain was replaced in 1978 by the CMI strain, which came from CBS.
Finally, there might be a practical reason to maintain the epithet "pulverulentum" because it has been used in many applied studies, especially in Sweden. However, even if S. pruinosum could be accepted as a distinct species, there are several other names available, which antedate S. pulverulentum, viz. Emmonsia brasiliensis and E. ciferrina.
Although the arguments in favour of the synonymy of S. pulverulentum and S. pruinosum are more convincing than those against it, the matter is not solved. Preliminary results of exo-antigen tests seem to indicate a difference. The use of the teleomorphic name Phanerochaete chrysosporium in applied studies is preferable as no controversies are connected with that name.
The reaction with a-naphthol is variable (Table 3); it varies from a distinct open ring to no reaction at all, while some strains show a faintly coloured spot; these reactions are normally read as negative, but in this discussion they are noteworthy. Phanerochaete chrysosporium causes a white rot and thus is able to produce phenoloxidases. However, these enzymes could neither be detected with the Bavendamm tests (gallic and tannic acid agar) nor with syringaldazine or gum guaiac (Burdsall & Eslyn, 1974).

Rypacek (1966) distinguished two types of white rot fungi: those which degrade lignin first and those which start with cellulose. This corresponds with the grouping of Ander and Eriksson (1977), who classified the white rot fungi after the production of endo-glucanase and phenoloxidase. Sporotrichum belongs in Rypacek's second group and produces much endo-glucanase and relatively little phenoloxidase.
The thermotolerant S. pruinosum (as S. pulverulentum or Ph. chrysosporium) has been the subject of many physiological studies (Kirk et al., 1978, 1980). Eriksson (1978) listed three types of hydrolytic enzymes for the degradation of cellulose: endo-1,4-fl-glucanase, exo-1,4-fl-glucanase and 1,4-/l-glucosidase. The species is used as a model for the biodegradation of lignin and the production of protein on lignocellulosic waste material (single-cell protein).
Keyser et al. (1978) found, that ligninolytic (phenoloxydase) activity was not dependent on the presence of lignin, but on nitrogen. Essential protein components of the ligninolytic system are synthesized as part of a series of physiological events that are initiated by nutrient nitrogen starvation. A 100% oxygen atmosphere stimulates the ligninolytic activity and agitation suppresses it. Eriksson et al. (1980) also used cellulose-less mutants in their studies.
The nutritional value of S. pruinosum for mammals (rats, pigs and sheep) was investigated by Thomke et al. (1980); the nutritive value was more satisfactory for sheep than for monogastric species, due to the cell wall structure of S. pruinosum. Ek and Eriksson (1980) developed a laboratory model for water purification and protein production on lignocellulosic waste waters, and Yang et al. (1980) for protein production on mechanical pulps of both angiospermous (Alnus) and gymnospermous (Tsuga) wood.
S. pruinosum has occasionally been reported as a human pathogen (Batista et al., 1963); it was isolated from lungs and caused adiaspiromycosis.
 
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