Fungal Growth and SporulationFungal Growth and Sporulation

G. T. Cole. 1986. Microbiol. Rev. 50: 95-132

From: Fischer-Parton et al. 2000. J. Microscopy 198 (3): 246-259

Exocytosis—enzymes (pectinases, cellulases, proteases) to degrade compounds in the environment

Endocytosis—removal of excess plasma membrane, recycling membrane proteins, transport of membrane proteins & lipids to vacuole for degradation, uptake of molecules, etc.

?

Mannoproteins

Glucan synthase

Wall-lytic enzymes, protease activators

Chitosomes (chitin synthase)

Multivesicular bodies

Wall substrates

Enzyme activators (GTP), inhibitor

Delivered from cytosol?

Components probably delivered by membrane-bound vesicles

Delivered from cytosol?

plasmalemma

wall

Components of wall synthesis at hyphal tip. Modified from Deacon (2006). Fungal Biology.

Asexual SporulationAsexual Sporulation

Sporangiospores formed by cleavage of Sporangiospores formed by cleavage of protoplasm in a multinucleate sporangium protoplasm in a multinucleate sporangium (Chytridiomycota, Zygomycota, Oomycota)(Chytridiomycota, Zygomycota, Oomycota)

Conidia develop directly from hyphae or Conidia develop directly from hyphae or from modified hyphal cells called from modified hyphal cells called conidiogenous cells (Ascomycota conidiogenous cells (Ascomycota including Deuteromycetes, some including Deuteromycetes, some Basidiomycota)Basidiomycota)

Control of asexual sporulationControl of asexual sporulation

May be triggered by changes in carbon:nitrogen May be triggered by changes in carbon:nitrogen ratio in growth mediumratio in growth medium

May require light trigger, e.g. near-ultraviolet May require light trigger, e.g. near-ultraviolet lightlight

Under control of sporulation genes:Under control of sporulation genes: One group involved in switch from somatic growth to One group involved in switch from somatic growth to

sporulationsporulation A second group regulates developmental stages of A second group regulates developmental stages of

sporulationsporulation A third group regulates secondary aspects including A third group regulates secondary aspects including

spore colorspore color

Asexual Fungi: Asexual Fungi: DeuteromycetesDeuteromycetes

DeuteromycetesDeuteromycetes““deuterdeuter-” Gk., meaning “second”-” Gk., meaning “second”

> 20,000 species of fungi in 2600 genera > 20,000 species of fungi in 2600 genera have no known sexual state have no known sexual state

Most belong in phylum AscomycotaMost belong in phylum AscomycotaThese fungi are also called:These fungi are also called:

Anamorphic fungiAnamorphic fungiMitosporic fungiMitosporic fungiConidial fungiConidial fungi Imperfect fungiImperfect fungiFungi imperfectiFungi imperfecti

Asexual propagulesAsexual propagules

ChlamydosporeChlamydospore 1-celled spore (usually 1-celled spore (usually

thick-walled) designed for thick-walled) designed for perennation; formed perennation; formed inside existing cellinside existing cell

Sclerotium (pl. sclerotia)Sclerotium (pl. sclerotia) Rounded mass of hyphae, Rounded mass of hyphae,

often differentiated into often differentiated into rind and medullarind and medulla

Asexual propagulesAsexual propagules

Conidium (pl. conidia)Conidium (pl. conidia) Non-motile spore Non-motile spore

designed for dispersaldesigned for dispersal Wide range of shape, Wide range of shape,

size, color and size, color and septation among taxaseptation among taxa

Saccardoan Spore TypesSaccardoan Spore Types

P.A. Saccardo (1845-P.A. Saccardo (1845-1920)1920) ““Sylloge Fungorum” Sylloge Fungorum”

(1882-1972)--names & (1882-1972)--names & descriptions of all descriptions of all known fungiknown fungi

Developed system of Developed system of classifying fungi based classifying fungi based on type of spore on type of spore (shape, septation, (shape, septation, color)color)

Saccardoan Spore TypesSaccardoan Spore Types

ColorColor Hyaline or bright (hyalo-)Hyaline or bright (hyalo-) Pigmented (phaeo-)Pigmented (phaeo-)

Shape and septationShape and septation 1-celled—amerospore1-celled—amerospore 2-celled—didymospore2-celled—didymospore Multicelled—phragmosporeMulticelled—phragmospore Muriform—dictyosporeMuriform—dictyospore Filiform—scolecosporeFiliform—scolecospore Helical—helicosporeHelical—helicospore Branched--staurospore Branched--staurospore

Saccardoan Spore TypesSaccardoan Spore Types

amerosporestaurospore

helicospore

scolecospore

dictyospore

didymospore

phragmospore

SynanamorphSynanamorph

Two or more types of Two or more types of asexual spores asexual spores formed by the same formed by the same fungusfungus

Example:Example: Ceratocystis fibriataCeratocystis fibriata

Conidiogenous CellsConidiogenous Cells

A cell that forms one A cell that forms one or more conidiaor more conidia

May be formed on a May be formed on a specialized simple or specialized simple or branched hypha branched hypha called a conidiophorecalled a conidiophore

From D. Malloch

Conidial Development (Ontogeny)Conidial Development (Ontogeny)

Blastic—blowing out of conidial initial prior Blastic—blowing out of conidial initial prior to formation of delimiting septumto formation of delimiting septum

Thallic—conversion of segment of existing Thallic—conversion of segment of existing hyphae into conidiahyphae into conidia

Blastic versus thallic Blastic versus thallic

Cole, 1986

Blastic developmentBlastic development

HoloblasticHoloblasticsingle conidium is formed from conidiogenous single conidium is formed from conidiogenous

locus, all wall layers involved in formation of locus, all wall layers involved in formation of conidium wallconidium wall

EnteroblasticEnteroblasticmore than one conidium formed from locus, more than one conidium formed from locus,

only the inner wall layer(s) involved in only the inner wall layer(s) involved in formation of conidium wallformation of conidium wall

From Hawksworth et al., 1995

Holoblastic

From Hawksworth et al., 1995

Holoblastic/synchronous

Holoblastic/sympodial

Enteroblastic developmentEnteroblastic development

PhialidicPhialidic—a basipetal —a basipetal succession of conidia succession of conidia is formed from a fixed is formed from a fixed locus on the locus on the conidiogenous cell conidiogenous cell (phialide)(phialide)

collarette

Enteroblastic developmentEnteroblastic development

AnnellidicAnnellidic—a —a basipetal succession basipetal succession of conidia formed by of conidia formed by repeated percurrent repeated percurrent proliferation of proliferation of conidiogenous locus, conidiogenous locus, leaving the distal end leaving the distal end of locus with of locus with transverse scars transverse scars (annellations)(annellations)

Enteroblastic developmentEnteroblastic development

TreticTretic—the inner wall —the inner wall of the conidiogenous of the conidiogenous cell blows out through cell blows out through a hole (pore) in the a hole (pore) in the outer wall like a outer wall like a balloon to form a balloon to form a conidium.conidium.

Arrangement of conidia at locusArrangement of conidia at locus

Solitary Solitary Catenate = true chainsCatenate = true chainsSeriate = false chains, spore headsSeriate = false chains, spore heads

Dry sporesDry sporesWet spores (gleoid)Wet spores (gleoid)

Succession of conidiaSuccession of conidia

Basipetal Basipetal = a chain of conidia in which new = a chain of conidia in which new spores are formed at the base, the oldest spores are formed at the base, the oldest conidia are at the apexconidia are at the apex

AcropetalAcropetal = a chain of conidia with the new = a chain of conidia with the new spores formed at the end of the chain, oldest spores formed at the end of the chain, oldest spores are at the base. In order for this type of spores are at the base. In order for this type of conidial formation to occur, the conidia must conidial formation to occur, the conidia must function as conidiogenous cells (e.g., function as conidiogenous cells (e.g., AlternariaAlternaria, , CladosporiumCladosporium))

Alternaria

Alternaria

Cladosporium

ConidiophoresConidiophores

Hyphae bearing conidiogenous cellsHyphae bearing conidiogenous cellsMorphologically differentiated from vegetative Morphologically differentiated from vegetative

hyphae (=macronematous)hyphae (=macronematous)Morphologically not differentiated Morphologically not differentiated

(=micronematous)(=micronematous)

ConidiophoresConidiophores

Types of DeuteromycetesTypes of Deuteromycetes

HyphomycetesHyphomycetes—fungi that produce —fungi that produce conidia from conidiogenous cells free on conidia from conidiogenous cells free on their myceliatheir myceliaMay be formed on the surface of May be formed on the surface of synnematasynnemata

or or sporodochiasporodochiaCoelomycetesCoelomycetes—fungi that produce conidia —fungi that produce conidia

from conidiogenous cells formed in from conidiogenous cells formed in conidiomataconidiomata

SynnemataSynnemata

Conidiophores united Conidiophores united at baseat base

Conidiogenous cells Conidiogenous cells at apexat apex

SporodochiumSporodochium

A compact, cushion-A compact, cushion-like aggregation of like aggregation of hyphae on which hyphae on which conidiophores are conidiophores are formed in a dense formed in a dense layerlayer

The aggregation of The aggregation of hyphae is called a hyphae is called a stroma (pl. stromata)stroma (pl. stromata)

HyphomycetesHyphomycetes

MoniliaceaeMoniliaceae—conidiophores formed singly, —conidiophores formed singly, hyphae and conidia pale-coloredhyphae and conidia pale-colored

DematiaceaeDematiaceae—conidiophores formed singly, —conidiophores formed singly, hyphae and/or conidia dark-coloredhyphae and/or conidia dark-colored

TuberculariaceaeTuberculariaceae—conidiophores aggregated —conidiophores aggregated on cushion-like sporodochium (pl. sporodochia)on cushion-like sporodochium (pl. sporodochia)

StilbaceaeStilbaceae—conidiophores aggregated in a —conidiophores aggregated in a synnema (pl. synnemata), an erect bundle with synnema (pl. synnemata), an erect bundle with conidia formed at apexconidia formed at apex