Assignment on

Classification and importance of fungal spores

Submitted to Dr. Abhishek

Submitted byAjay Rai (4929)

DIVISION OF BACTERIOLOGY AND MYCOLOGYINDIAN VETERINARY RESEARCH INSTITUTE

IZATNAGAR – 243 122.

WELCOME ALL

OUTLINE• Introduction• Classification of spore• Classification of Asexual spore• Classification of Sexual spore• Importance

INTRODUCTION • Spore formation is one of method of reproduction in

fungi.

• Spores are generally more resistant to adverse environmental conditions.

• Spores represent microscopic dispersal (sporangiospores and conidia) or dormant (oospores and Zygospore) survival propagules produced by most species of fungi.

• Fungal spores may be unicellular or multicellular e.g. conidia produced by Alternaria species are multicellular.

• Some spores possess a textured or ornamented surface e.g. uredospores of Melampsora epita.

CLASSIFICATION There are two types of spore formed in fungi- (1)Asexual spore (2)Sexual spore (1)Asexual spore • Sporangiospores • Conidia (2)Sexual spore • Ascospore• Basidiospore• Zygospore• Oospore

Asexual spores

Asexual spores may be divided into two broad categories-(1)Sporangiospore(2)Conidia

(1) Sporangiospore •zoospores (motile) & •Aplanospore (non-motile) (2) Conidia•Thallic conidia •Blastic conidia

(1) Sporangiospores:- • If the spores develop within a sac (sporangium, Pl. sporangia)

at a hyphal tip, they are called sporangiospores. • A sporangium is a sac-like structure whose entire contents

are converted through cleavage into one or more, usually many spores.

• Endogenously formed • Formed as a result of the cleavage of protoplasm around

nuclei.

• Followed in some cases by formation of a wall around each nucleate portion of protoplasm.

• Characteristic of fungi belonging to the chytridiomycota, oomycota and hyphochytridiomycota.

• Two main types – ZOOSPORES (motile) and APLANOSPORES (non-motile)

(i) Aplanospore :- • Nacked, thin walled, single celled uni or multinucleate, nonmotile spores• It can be of different shape and size.

(ii) Zoospores:-

• Zoospores are motile sporangiospores and the sporangia in which they form are called zoosporangia.

• The protoplasm of zoospores is not surrounded by a wall that's why in some aspects they resemble flagellate protozoa.

• Because zoospores are motile, the fungi that produce them will require water at some stage during their life cycle.

• Zoospores may be uniflagellate or biflagellate- (a) Uniflagellate zoospore -flagellum are mostly posteriorly

placed except in few where it is at anterior end. (b) Biflagellate zoospore – one flagellum anterior and other

posterior.

--Usually anterior placed flagellum has fine haires and is called “Tinsel flagellum”. Fine haires are called “Flimmer” or “Mastigonems”.

-- Posterior flagellum consist of long, relatively thick rod which narrows abruptly at its tip to a delicate prolongation of variable length known as “whiplash flagellum”

• Three different types of zoospore distinguish the Chytridiomycota, Hyphochytridiomycota and Oomycota.

(2) Conidia -•If spores are not enclosed in a sac but produced at tips or sides of hyphae they are termed conidia (sing. Conidium).

•Exogenous - often formed at the tip of supporting hyphae called a “Conidiophores “.

•Develop in a variety of ways.

•Characteristic of MITOSPORIC FUNGI and fungi belonging to the ASCOMYCOTA and BASIDIOMYCOTA.

• Two main types - Thallic and Blastic conidia (I) Thallic Conidia –• develop by septation and fragmentation of a hypha.

• may develop at the tip of a hypha or in an intercalary (central) position.

• in both cases, all layers of the hyphal wall are involved in spore formation.

(a) Arthrospores (Oidia) :-• Formed by septation and fragmentation of an existing hypha. • Elements of the hypha (incl. all wall layers) become converted

into conidia. • Each fragment is rounded off and liberated in succession. • Separation of the conidia from one another is due to

breakdown of the middle region of each septum.

(b) Chlamydospores : -• A type of resting or survival spore. • Found in several groups of fungi (e.g. Zygomycota and

mitosporic fungi). • An intercalary (see diagram) or apical hyphal cell or

compartment enlarges, rounds up and develops a thickened, often pigmented wall.

• Contain dense cytoplasm and nutrient storage compounds. • Thick-walled (All wall layers are involved in their formation). • Become isolated from adjacent hyphal compartment(s) by the

sealing of septal pores (if present). • Usually develop under conditions of stress that are

unfavourable for normal somatic growth.

(ii) Blastic Conidia • Develop by a BUDDING or SWELLING PROCESS. • May develop as SINGLE SPORES or in succession to form a CHAIN OF SPORES. (a) Blastospores: • Formed by budding of a hypha or yeast cell. • Both wall layers are involved. • The spore may remain attached and bud further blastospores

- giving rise to a branched chain of spores.

(b) Porospores:-• The developing spore emerges through a distinct 'pore' in

the hyphal wall. • Only the inner layer of the hyphal wall is involved in spore

development. • The new spore then develops its own new inner wall layer. • The outer spore wall is often thickened and pigmented. • A scar is usually obvious at the point of detachment from

the hypha (conidiospore).

(c) Aleuriospores :-• Develop as single, terminal spore. • Conidiophore apex inflates and becomes separated by a

septum at an early stage in spore development. • Both wall layers are involved in spore formation . • The spore possesses a wide, truncate scar. • Normally no further development of spores occurs at the point

of detachment. • So the next spore usually has to develop by production of a

branch below the scar on the conidiophore.

(d) Annellospores :-• In some species that form conidia in a manner similar to that

described for aleuriospores (before) a new growing point does develop at the scar.

• A chain of spores may develop. • The conidiophore gets a little longer with each spore

produced. • Annellations (ring-like scars) are observed around this

elongating portion. • Each annellation represents the production of one

annellospore.

(e) Phialospores:-• Form in succession . • Each spore is pushed up from the tip of the conidiophore, which is now called a PHIALIDE. • The spore wall is new and distinct from both wall layers of the phialide. • The first spore has a cap, which represents the tip of the

phialide wall through which the spore emerged - all other spores in the chain are smoothly rounded.

Sexual spores• Sexual reproduction in most of the fungi involves the formation

of specialized spores.• There are four types of sexual spores are described-(1) Ascospore(2) Basidiospore(3) Zygospore(4) Oospore

(1) Ascospore:-• Fusion of male and female gamete results in the formation of

egg, which through successive divisions, generate spores. If the spores remain in the egg, which is then called as ascus, they

are referred to as “ASCOSPORES”.• Produce one to eight ascospores in a single, round ascus.

• Simplest representative of this class is SACCHROMYCES.

• Majority of ascomycetes develop septate mycelia with several club-shaped ascospores enclosed in a fruiting body called “ASCOCARP”.

---Completely closed ascocarp-CLEISTOTHECIUM ---Saucer or cup-shaped ascocarp that is completely opened

at maturity- APOTHECIUM ---spherical or flask shaped ascocarp with a pore opening –

PERITHECIUM.

(2) Basidiospore:- • Develop in club-shaped structure called basidium (Pl. basidia)• Basidium is a structure bearing on its surface a definite

number of basidiospores (typically four) that usually are formed following karyogamy and meiosis.

• Characteristic of class basidiomycetes which includes mushrooms, toadstools and bracket fungi.

(3) Zygospore (thick walled resting spore)- • When the tip of neighbouring hyphae join and the contents fuse with the pairing of nuclei, a new cell develops with thick, pigmented, rough walls. This structure is called Zygospore.

• This pattern of reproduction is common to mucor, absidia and Rhizopus of class zygomycetes and the order mucorales.

(4) Oospore (thick walled resting spore) –•A thick-walled spore that develops from an oosphere through either fertilization or parthenogenesis. •Oosphere is a large , naked, nonmotile female gamete.•Zygospore and Oospore both are thick walled resting spores but difference is that Zygospore is resulting from the fusion of two similar gametes and Oospore is developed as a result of two unlike cells.

Importance of Spores

A. Biological: 1) Allows for dissemination

2) Allows for reproduction 3) Allows the fungus to move to new food source. 4) Allows fungus to survive periods of adversity. 5) Means of introducing new genetic combinations into a

population. Practical

B. Practical: 1) Rapid identification (also helps with classification). 2) Source of inocula for human infection. 3) Source of inocula for contamination

C. Commercial: •Fungal spores possess a wide range of CONSTITUTIVE ENZYMES.

•These enzymes increase in metabolic activity that accompanies germination, has resulted in spores being used as biological catalysts in a number of commercial CHEMICAL TRANSFORMATION processes. Examples:- The transformation of penicillins by spores of Fusarium moniliforme.

The conversion of fatty acids to methylketones by spores of Penicillium roquefortii.