Stemphylium species

Stemphylium species (Hyphomycetes)

Ecology:

Stemphylium species are widely distributed in nature and can be found in soils as well as plant parasites and as saprophytes on decaying plant material.  As a plant pathogen, Stemphylium species are implicated in the leaf spot of alfalfa (S.botryosum), black rot of carrots (S.radicinum), and grey leaf spot of the tomato plant (S.solani).

Pathogenicity:

Stemphylium species found in the clinical laboratory are generally considered to be contaminants; however, they may contribute to allergic reactions in general and have been reported as agents of phaeohyphomycotic sinusitis. 

Macroscopic Morphology:

Colonies on SAB are velvety to cottony with a rather short ‘nap’ (does not extend very high above the agar surface).  They are olivaceous (grey-green-brown) to a brownish-black in surface colour.  The reverse is black.  Stemphylium species exhibit a moderate growth rate, becoming mature within five days.

Stemphylium species - 1 Week on SAB at 30^oC (Nikon)

Microscopic Morphology:

Hyphae are septate and develop a pale brown to deeper brownish colour as they age.  Conidiophores also show septations and the structure is simple or occasionally branched.  The cell at the apex of the conidiophore which bears the conidium may show a slight swelling in relation to the rest of the conidiophore.  The conidiophore which generally shows somewhat smooth and parallel walls when young may develop a much more knobby appearance as it ages and produces conidia.  Conidia (12 – 20 µm X 15 – 30 µm) are produced by growing from the tip of the terminal conidiogenous cell (poroconidia).  They can be smooth or rough (echinulate) in texture.  They have been described as oval, oblong, ellipsoidal, obclavate and subspherical.  More simply they may be described as ‘box-like’ with rounded corners.  The conidia may also show a marked constriction around a central septum or division within individual conidia. The conidia are muriform (both transverse and longitudinal septations or divisions), and acquire a dark brown pigment as they mature.  

Caution: Micron scale (µm) may change between 50 or 100 µm at higher magnifications.

Stemphylium species - not much to distinguish between other moulds in this photo.  I've added it just to show the tangled mass of the mycelium that fungi produce.  Conidia are visible as the dark spots but features are indistinguishable at this magnification. 

 (250X, LPCB, DMD-108)

Stemphylium species - edge of a slide culture showing hyphae growing out from the edge of the SAB block from which conidiophores extend and produce pigmented conidia at the ends.

(250X, LPCB, DMD-108)

Stemphylium species -another shot showing numerous pigmented conidia sitting on the ends of the conidiophores which extend at right-angles from the supporting vegetative hyphae.

(250X, LPCB, DMD-108)

Stemphylium species -more detail emerges at this higher magnification.  Septations become visible in the pigmented conidia.

(400X, LPCB, DMD-108)

Stemphylium species -hyphae and conidiophores.

(400+10X, LPCB, DMD-108)

Stemphylium species -rather short conidiophores, extend primarily at right-angles from the parent vegetative hypha.  At the lower left corner there is a branched conidiophore with a rather young, still unpigmented, conidium developing on the left branch. Two more young conidia can be seen in the photo as well.

(400X, LPCB, DMD-108)

Stemphylium species -a few more photos to leave you with an impression of what Stemphylium looks like.  Conidia can be longer and branched which distinguishes it from Pithomyces species.  The shape of the conida also is different from Pithomyces - discussed in later photos.

(400X, LPCB, DMD-108)

Stemphylium species -brown pigmented conidia at the apices of individual conidiophores extending from an 'out of focus' hyphal element.

(400X, LPCB, DMD-108)

Stemphylium species -conidiophores extending from the supporting vegetative hyphae with conidia at various stages of maturity.  Young, blue-stained conidia and brown pigmented mature conidia are present.  (400X, LPCB, DMD-108)

Stemphylium species -ditto. 

(400X, LPCB, DMD-108)

Stemphylium species -self indulgence here.  More photos to demonstrate the same,  Conidiophores with mature pigmented conidia at the tips.  Muriform (longitudinal & transverse) septation is apparent.  (400X, LPCB, DMD-108)

Stemphylium species -the appearance in this photo is very similar to that of Pithomyces species in that there are conidia at the ends of short conidiophores arising at right-angles to the hyphae from which they extend.  Darkly pigmented conidia have internal compartments made by the muriform (both up and down and across) septations.  The pigmented hyphae to the left of the photo is clearly septate and appears to be releasing it's pigment into the medium (brown haze).

(400X, LPCB, DMD-108)

Stemphylium species -as above. 

Stemphylium species -massive amounts of conidia can be produced as seen here.

(400X, LPCB, DMD-108)

Stemphylium species - a slightly closer look.  Muriform septations evident in the mature brown conidia.  The shape has been described as oval, oblong, ellipsoidal, obclavate and subspherical.  More simply they may be described as ‘box-like’ with rounded corners.

(400+10X, LPCB, DMD-108)

Stemphylium species - The conidiophore which generally shows somewhat smooth and parallel walls when young may develop a much more knobby appearance as it ages and produces conidia (lower left).  (400+10X, LPCB, DMD-108)

Stemphylium species - mature brown box-like conidia at the ends of somewhat knobby conidiophores.  (400+10X, LPCB, DMD-108)

Stemphylium species - conidia with muriform septations.

(400+10X, LPCB, DMD-108)

Stemphylium species - ditto, as above.

(400+10X, LPCB, DMD-108)

Stemphylium species -the conidia may also show a marked constriction around a central septum or division within individual conidia (arrows).

(400+10X, LPCB, DMD-108)

Stemphylium species -  conidia (12 – 20 µm X 15 – 30 µm, when mature) are produced by growing from the tip (arrow) of the terminal conidiogenous cell (poroconidia).

(1000X, LPCB, DMD-108)

Stemphylium species - here on another conidiophore you can see the conidium (poroconidium) increasing in size as it develops.  Internal septations have yet to develop.

(1000X, LPCB, DMD-108)

Stemphylium species - branching conidiophore -mature brown conidia and a smaller and younger, pale blue conidium.  To follow along from the last two photos, the pale blue conidium is developing further and starting to develop a transverse septum (light line crossing the inside of the small blue conidium).  (400+10X, LPCB, DMD-108)

 Stemphylium species - Mature brown muriform septate conidia showing central construction along where the transverse septum crosses.  Conidiophores may develop a knobby appearance with maturity and the cell at the apex of the conidiophore which bears the conidium may show a slight swelling in relation to the rest of the conidiophore.

(1000X, LPCB, DMD-108)

 Stemphylium species - as above.

(1000X, LPCB, DMD-108)

Stemphylium species -  As above.  Different stages of maturity.  Too many photos, I know!

(1000X, LPCB, DMD-108)

Stemphylium species - ditto.

(1000X, LPCB, DMD-108)

Stemphylium species - conidia can be smooth or rough (echinulate) in texture.

(1000+10X, LPCB, DMD-108)

Stemphylium species - can be smooth or rough (echinulate) in texture. Conidiogenous cell at tip of conidiophore may be somewhat distended (wider, swollen) in relation to the rest of the conidiophore.

(1000+10X, LPCB, DMD-108)

Stemphylium species - conidiophore shows septation.

(1000+10X, LPCB, DMD-108)

Stemphylium species - again, conidiogenous cell closest to the tip may show a slight swelling in relation to the rest of the conidiophore.

(1000+10X, LPCB, DMD-108)

Stemphylium species - conidia with various surface textures.

(1000+10X, LPCB, DMD-108)

Stemphylium species - yet another photo!  You get the picture by now...

(1000+10X, LPCB, DMD-108)

Stemphylium species

(1000+10X, LPCB, DMD-108)

 Stemphylium species

Stemphylium species - poroconidium (doesn't show the annular frill which is seen on somewhat similar looking muriform conidia produced by Pithomyces species.

(1000+10X, LPCB, DMD-108)

 Stemphylium species - looks like a degenerating, rather wilted conidiophore.

(1000+10X, LPCB, DMD-108)

Stemphylium species- branching septate conidiophore.

(1000+10X, LPCB, DMD-108)

 Stemphylium species - branching conidiophore.

(1000+10X, LPCB, DMD-108)

Stemphylium species

(1000+10X, LPCB, DMD-108)

 Stemphylium species 

(1000+10X, LPCB, DMD-108)

 Stemphylium species 

(1000+10X, LPCB, DMD-108)

 Stemphylium species 

(1000+10X, LPCB, DMD-108)

Stemphylium species -Last one.  I don't know what I was thinking, uploading some 45 photos to illustrate Stemphylium species.  As with most of the posts in this blog, the photos posted represent only 10% of what I've taken.  Sorry for anyone who I lost with boredom -I find the little critters fascinating.

(1000+10X, LPCB, DMD-108)

Note: May be confused with other darkly pigmented moulds such as Alternaria species, Pithomyces species, and Ulocladium species (see table below).

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Pithomyces species

Pithomyces species  -Hyphomycete

Ecology:

The genus Pithomyces has approximately 50 recognized species to date.   Speciation is most accurately achieved by molecular means; however, careful observation of morphological features can identify this mould to the genus level.

Pithomyces species are dematiaceous saprobes (darkly pigmented moulds which commonly grow on dead organic matter) and may be found on the leaves and stems of a variety of plants. They have also been isolated from decaying wood, tree bark (Acacia) and from soil.

Pathogenicity:

Pithomyces species have been implicated in human disease however their role has not been sufficiently substantiated.  Pithomyces has reportedly been isolated from finger and toe nails, a hand lesion (skin scrapings), peritoneal fluid, bronchial washings, and from a chronic nasal polyposis. The mould may also contribute to general allergic reactions.  In the United States, the most commonly isolated Pithomyces species appear to be P. chartarum, P. sacchari, and P. maydicus.

Pithomyces species have been implicated in pithomycotoxicosis (facial eczema) of ruminants such as sheep, cattle and goats.  P.chartarum, in particular is considered the cause of facial eczema in sheep.

Pithomyces species are commonly considered to be laboratory contaminants, however, they should not be ruled out without careful consideration, particularly in immunocompromised patients.

Macroscopic Morphology:

Pithomyces exhibits fairly rapid growth, maturing in about five days to a week.  Colonies on SAB at 30ᵒC are olivaceous, light to dark brown to brownish-black.  Colour is species and media dependant.  Dark brown to black areas, may be seen macroscopically on some species (P. atro-olivaceus), revealing sporodochia (pleural of sporodochium), which are areas of greater conidial production.  The overall colonial texture is downy to cottony, with a short feathery nap (effuse).  The reverse is brown to brownish-black in colour.

The isolate presented in this blog (SAB 30ᵒC) post had a lighter cream coloured fringe or edge to the colony.

 Pithomyces species - Sabouraud-Dextrose Agar (SAB), 1 Week, 30ᵒC (Nikon)

Microscopic Morphology:

Pithomyces species produce septate, sub-hyaline (pale to light brown) hyphae.  Conidiophores are generally short (peg-like, ~10 µm length), and rather poorly differentiated from the vegetative hyphae from which they extend.  Conidia (10 – 17 µm X 18 – 30 µm) are produced singly at the apex of the conidiophore where they are attached by a short denticle.  After conidial dehiscence (release of conidia), a visible annular frill may remain at the conidial base where once attached to the conidiophore.  Conidia are muriform (have both longitudinal and transverse septations) and are broadly ellipsoidal to ovate (egg shaped) or pyriform (pear shaped) in shape.  P.chartarum usually exhibits 2 – 5 transverse septa with 0 – 3 longitudinal septa. The muriform or septation pattern may be species dependant; P. atro-olivaceus may only produce horizontal septa.  Conidia are dark brown in colour when mature and usually have an echinulate (spiny or prickly) or verruculose/verrucose (warty) texture. 

Caution: Micron scale (µm) may change between 50 or 100 µm at higher magnifications.

 Pithomyces species - Initial view -growth from the edge of a slide culture.

(250X, LPCB, DMD-108)

Pithomyces species - darkly pigmented conidia with internal septations are seen.

(400X, LPCB, DMD-108)

Pithomyces species - Numerous, pigmented conidia seen.  Insert shows the muriform (both longitudinal and transverse septa) septations.

(400X, LPCB, DMD-108)

Pithomyces species - after conidial dehiscence (release of conidia), a visible annular frill may remain at the conidial base where once attached to the conidiophore.  (400X, LPCB, DMD-108)

Pithomyces species - conidia are broadly ellipsoidal to ovate (egg shaped) or pyriform (pear shaped) in shape. (400X, LPCB, 400X)

Pithomyces species - Conidia are borne on short stalks. Brownish pigment has exuded from the hyphae and can be seen as the brown haze alongside the hypha. (400X, LPCB, DMD-108)

Pithomyces species - conidiophores are generally short (peg-like, ~10 µm length), and rather poorly differentiated from the vegetative hyphae from which they extend.  (400X, LPCB, DMD-108)

Pithomyces species - as above.  (400+10X, LPCB, DMD-108)

Pithomyces species - conidia (10 – 17 µm X 18 – 30 µm) are produced singly at the apex of the conidiophore where they are attached by a short denticle.  (400+10X, LPCB, DMD-108)

Pithomyces species - septate hypha with pigment seen along the outer walls of several. Conidium on short stalk is seen at center right. (400+10X, LPCB, DMD-108)

Pithomyces species - single, elongated conidium seen at the apex of a withering hyphal element or conidiophore. (400+10X, LPCB, DMD-108)

Pithomyces species - some chains appeared to be formed by this particulate isolate. Only one source I consulted (Davone -see sidebar) stated that Pithomyces species do not chain. I isolate presented here conforms to the characteristics described for Pithomyces with the exception of chain formation by the conidia. This should not be confused with the chain-like formation of conidia as seen in Alternaria species. (400+10X, LPCB, DMD-108)

Pithomyces species - ditto.

(400+10X, LPCB, DMD-108)

Pithomyces species - yet another photo at higher magnification...
(1000X, LPCB, DMD-108)

Pithomyces species - oval conidium at apex of a short stock which shows little differentiation from the vegetative hyphae. (1000X, LPCB, DMD-108)

Pithomyces species - pigment escaping from the hyphae into the surrounding medium.
Vegetative mycelium composed of thin-walled hyaline, septate, smooth or verrucose, septate hyphae, 4–7 µm diameter, which may give rise to chains of verrucose, one-celled, dark brown, intercalary chlamydospores 10 -20 µm X 8 - 18 µm[i].

(1000X, LPCB, DMD-108)

Pithomyces species - pigment escaping from the septate hyphae into the surrounding medium.  Annular frill can be seen attached to the anterior end of the conidium.
(1000X, LPCB, DMD-108)

 

Pithomyces species - more intercalary chlamydospores seen as described two photos above.
(1000X, LPCB, DMD-108)

 

Pithomyces species - Conidia are dark brown in colour when mature and usually have an echinulate (spiny or prickly) or verruculose/verrucose (warty) texture.  The conidium at center-right clearly shows a spiny or prickly surface.  Intense uptake of the Lactophenol Cotton Blue (LPCB) dye somewhat obscures the muriform septations within the conidium.

Pithomyces species - appears to be attached at both ends which would make it an intercalary chlamydospore (?)
 (1000+10X, LPCB, DMD-108)

Pithomyces species - short, peg-like, conidiophores arising from the vegetative hyphae at right-angles with single pigmented, muriform conidium at each apex.
(1000X, LPCB, DMD-108)

Pithomyces species -here you get it all as described in previous photos.  Pigmented septate hyphae with pigment escaping into the surrounding medium.  Prickly surfaced muriform conidia borne singly on short peg-like conidiophores.  The free conidium closest to the top shows the annular frill which remains from where it was attached to the conidiophore.
(1000X, LPCB, DMD-108)

Pithomyces species -two, rather smooth walled, conidia attached to the hypha by short conidiophores.
(1000+10X, LPCB, DMD-108)

Pithomyces species - some chaining (?) evident.
(1000X, LPCB, DMD-108)

Pithomyces species - single muriform conidium at the end of a short conidiophore.
(1000+10X, LPCB, DMD-108)

Pithomyces species - single muriform conidium at the end of a short, rather twisted,  conidiophore.(1000+10X, LPCB, DMD-108)

Pithomyces species - conidia are borne singly at the ends of the conidiophores.
(1000+10X, LPCB, DMD-108)

Pithomyces species - I'm trying to figure this one out.  Are those two conidia arising from two, obscured, conidiophores, or is one an intercallary chlamydospore with a conidiophore & conidium arising from the same area of the hypha?.

Pithomyces species - Sources state that Pithomyces conidiophores produce single conidia.  Does this photo show a single conidium at the end of a short, pale pigmented conidiophore or is conidiphore the LPCB stained structure arising from the hyphae below with the apex of the conidiophore branched, and one conidium missing?  You decide...

(1000+10X, LPCB, DMD-108)

Pithomyces species -muriform conidia at the end of short peg-like conidiophores.
(1000+10X, LPCB, DMD-108)

Pithomyces species -conidia texture described as echinulate (spiny or prickly) or verruculose/verrucose (warty) texture.
 (1000+10X, LPCB, DMD-108)

 

Pithomyces species - conidia which aren't over-saturated with the LPCB stain and more clearly show the muriform septation within.

(1000X, LPCB, DMD-108)

Pithomyces species - thickened and roughened wall of the intercalary chlamydospores.
 (1000+10X, LPCB, DMD-108)

Pithomyces species - chaining of conidia (?) at left.  Two, rather young conidia on short peg-like conidiophores at lower center of photo.
 (1000+10X, LPCB, DMD-108)

Pithomyces species
  (1000+10X, LPCB, DMD-108)

Pithomyces species have to be differentiated from closely related dematiaceous hyphomycetes such as Ulocladium species, Stemphylium species, Alternaria species and Epicoccum species. (See Table Below)
 

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Alternatively, just click and download the damn thing...

[i] The Genus Pithomyces in South Africa

W.F.O. Marasas and Ingrid H. Schumann,

Bothalia 10, 4: 509 – 516, 1972

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