Sunday, 2 December 2012

Trichoderma species

Trichoderma species

Ecology:  Trichoderma species are widely distributed and are commonly isolated from soil.  Capable of degrading cellulose, Trichoderma species can also be found on decaying vegetative material including wood. 

Macroscopic Morphology:  Trichoderma species is a rapidly growing mould which matures in 3 to 5 days.  Growth begins as fluffy white tufts which then compact and appear woollier.  Green tufts may develop within the colony due to the production of conidia.  These often appear as concentric rings, typically starting at the edge of the colony.  The reverse is typically a light tan to yellow or pale orange.

 Trichoderma species -Sabouraud Dextrose Media (SAB) after about 72 hours incubation at 30o C. (Nikon)

Microscopic Morphology:  Trichoderma produces septate, hyaline hyphae.  Conidiophores are rather short, branching at wide angles (approaching 90o), often giving it a pyramidal appearance.  Phialides are flask or ampule shaped (inflated at the base), which again extend from the conidiophore at wide angles.  Conidia are round to ellipsoidal and can be smooth or rough walled depending on the species.  Single celled conidia (2-3 µm by 2.5 to 5 µm) are often green in colour and accumulate at the tips of the phialides in slimy balls.

 Trichoderma species - First glance at a slide culture after only 24 hours incubation.  Hyphae with phialides developing at near right angles.  Conidia yet to appear at the ends of the phialides.  (LPCB, 250X, DMD-108)

Trichoderma species - 48 hours slide culture showing conidia developing at the ends of the phialides.  Micron bar at upper right of photo.  (LPCB, 250X, DMD-108)

Trichoderma sp.- as above but at a higher magnification.  Conidia clustered around tips of the phialides.  (LPCB, 400X, DMD-108)

Trichoderma species - jumping up to a higher magnification, conidia are seen clustered around the tips of the phialides.  The size and extent of the branching conidiophores often takes a portion of the structure out of the focal plane of the camera.  Where this occurs shows as a blurry or out of focus structure.
(LPCB, 1000+10X, DMD-108)

Trichoderma sp. - conidiophores branching at near right angles, younger near the tip, gives the entire structure a pyramidal appearance (inset).
(LPCB, 1000X, DMD-108)

Trichoderma species - as above (LPCB, 1000X, DMD-108)

Trichoderma sp. - looking back at a young culture, the flask or ampule shaped phialides are not yet obscured by the conidia which develop and accumulate at their tip.
(LPCB, 1000X, DMD-108)

Trichoderma sp. - groups of the flask or ampule shaped phialides are seen in this photo.  At the risk of dating myself, the structure reminds me of the childhood game of 'Jacks' (inset).
(LPCB, 1000+10X, DMD-108)

Trichoderma sp. - another view showing near right angle (~90o) branching.  Phialides still devoid of conidia.  (LPCB, 1000X, DMD-108)

Trichoderma sp. (LPCB, 1000+10X, DMD-108)

Trichoderma species - septate hyphae visible.  Branching here appears to be somewhat less than a full 90o .  Conida remain clustered around most phialides though a few are already bare.  Over saturation of the blue colour (LPCB) is a photographic anomaly and could not be adequately remedied at the camera nor with a photo editing program.
(LPCB, 1000+10X, DMD-108)

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

Trichoderma species - one last photo showing the round clusters of conidia attached to the phialides.  Again the pyramidal shape is seen with longer branches to the left, tapering to the right of the photo.
(LPCB, 1000X, DMD-108)
 Pathogenicity: This organism is generally considered a contaminant of little medical importance; however immunocompromised patients may be at greater risk of infection.  Reports of peritonitis in patients undergoing peritoneal dialysis (CAPD) have been reported. It has also been isolated from a pulmonary cavity infection and a hepatic infection from a liver transplant recipient.

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