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The Zygomycetes

Elmer W. Koneman, M. D., USA

Manuela Anda Andrei, Romania

Romanian Society of Laboratory Medicine

2008 Congress -- Bucharest, Oct. 20 22

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The Zygomycetes

The Zygomyces are a group of fungi

that produce broad, aseptate hyphae and

bear spores within sack-like structures

called sporangia. In the perfect or

telomorphic form, they producezygospores (see photo).

They are widely distributed in soil,

dung, and vegetable matter. Humans

may become infected by inhaling spore-

contaminated dust (pulmonaryinfection), by ingesting contaminated

foodstuffs (GI infection) or by direct

inoculation of the skin (subcutaneous

infection).

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The Zygomycetes

Colonies of the Zygo-mycetes

grow rapidly over the entire

surface of the agar plate as

a gray-white, brown or

gray-brown, cottony orwooly colony, without a

distinct margin (lid lifter).

As the colony matures, the

mycelium may darken and

show a black pepper effectas a myriad of sporangia are

formed.

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The Zygomycetes

Microscopic Features

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MORPHOLOGY OF RHIZOPUS

Rapid border to border

growth on Sabouraud agar

Sproangiospores arise

singly or in groups

Rhizoids present at node

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ABSIDIA

Grows rapidly on Sabouraud agar

Sporangiophores branched

Rhizoids produced internodally

Sporangia pyriform, grayish brown togreenish beige

Columnella hemispherical

Apophysis distinctly conical Sporangiospores globose to cylindrical

and smooth

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MORPHOLOGY OF ABSIDIA

Grows rapidly on Sabouraud agarSporangiophores branched

Rhizoids produced internodally

Apophysis distinctly conical

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SYNCEPHALASTRUM

Grows rapidly on Sabouraud agar

Sporangiophores usually branched

and have swollen tips Cylindrical merosporangia produced

surrounding the swollen tip

Merospores produced within

merosporangia

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MORPHOLOGY OF

SYNCEPHALASTRUM

Sporangiophoresusually branched and

have swollen tips

Cylindrical

merosporangiaproduced surrounding

the swollen tip

Merospores produced

within merosporangia

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CUNNINGHAMELLA

Grows rapidly on Sabouraud agar

Conidiophores may be branched

Vesicles globose to subglobose

Sporangioles (conidia) are formed

on the surface of the vesicle

Conidia are echinulate

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MORPHOLOGY OF CUNNINGHAMELLA

Grows rapidly on

Sabouraud agar

Conidiophores may

be branched

Vesicles globose tosubglobose

Sporangioles

(conidia) are formed

on the surface of thevesicle

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MUCOR

Rapid growth on Sabouraud agar

Sporangiophores do not arise from stolon

Sporangiophores may be branched orunbranched

Rhizoids are not present

Sporangia globose, brownish to gray

Columella globose

Apophysis absent

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Rapid growth on Sabouraud agar

Sporangiophores do not arise from stolon

Sporangiophores may be branched or

unbranched

Rhizoids are not present

MORPHOLOGY OF MUCOR

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SAKSENAEA

Grows slowly and sporulates poorly on

Sabouraud agar

Rhizoids produced at base of sporangiophore

Sporangium is flask shaped, with long neck

Columella globose

Sproangiospores smooth and elongate

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MORPHOLOGY OF SAKSENAEA

Grows slowly and

sporulates poorly on

Sabouraud agar

Rhizoids produced at

base of sporangiophore

Sporangium is flask

shaped, with long neck

Columella globose

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REVIEW: ZYGOMYCETESCOLONY CHARACTERISTICS

Rapid growth in 3-5 days. Gray-

brown, wooly mycelium that fills the

Petri Dish. Pepper effect when

sporangia are produced.

MICROSCOPIC FEATURES

Hyphae are broad, ribbon-like,

irregular in diameter and devoid of

septations. Sporulation is via

production of sporangia.

LOOK FOR:

RHIZOIDS

PRESENT ABSENT

Nodal derivation of

sporangiophores.

Collapse of columella*******

RHIZOPUS

Branched

sporangio-

phhores; noapophysis

MUCOR

Spherical columella

and merosporangia

*******

SYNCEPHAL-

ASTRUM

Circular curve of

sporangiophores

*****CIRCINELLA

Large

spherical

sporangioles

******

CUNNING-

HAMELLA

Internodal derivation of

sporangiophores.

Apophysis present.

*******

ABSIDIA

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QUESTIONS/COMMENTS?