Chytrids and Oomycota

Zoospores

Nonsexual spores, flagellated, swarming stage, form a cyst, and cyst germinates to form a germ tube.

Tinsel Type

Whiplash Type

Chytrids

Asexual reproductive spores (zoospores) that swim by means of a posteriorly directed whiplash flagellum and taxonomy is based on the ultra structure of the zoospores.

Rhizoids/Rhizomycelium

root like structures that take in nutrients.

Asexual Reproduction

Zoosporangia can be operculate or inoperculate.

Sexual Reproduction

Plasmogamy, zygote forms a resting spore, and resting spore germinates and forms a zoosporangium.

holocarpic

The whole thallus becomes the reproductive cell.

Eucarpic

The thallus is differentiated into vegetative structures and reproductive structures

Monocentric

Have one sporangium

Polycentric

Have multiple sporangia.

Epibiotic

Sporangium is outside the cell

Allomyces

• Polycentric and Eucarpic

• Alternation of generations

• Gametothallus forms male and female gametangia

• Sporothallus forms 2 tyoes of sporangia: thin mitosporangia and thick meiosporangia

Bactarachochyytrium dendrobatidis

Parasitic fungus on a frogs skin that suffocates them to death by destroing their skin.

Oomycetes characteristics

• Diploid organisms for most of their life cycle

• Mycelia are aseptate

• Cell wall made of beta-glucans and cellulose

• an asexual spore is motile with flagella

• Sterols are not synthesized and replaced by long-chain fatty acids

• Production of sexual spores (Oospores) by fertilizarion of an oosphere by the antheridium.

Oomycota

• primarily fresh water organisms/ some are terrestrial

• 3 main lineages: Early diverging, Saprolegniales, Peronosporales, and Pythiales

• 5 major orders

• many pathogens

Auxillary zoospore

Pear-shaped and flagella are at the end.

Principal zoospore

Kidney-shaped and flagellum come out of the middle.

Saprolegniales

• Wet soil and fresh water

• Genera Saprolegnia and Aphanomyces

• Produce own sterold

• Mainly saprotrophs or pathogens of fish, fish eggs and plants

• Have both kinds of zoospores

• Cysts may germinate by forming another zoospore ot forming hyphae

• Create ich on fish

Oogonium

Female gametangium

Antheridium

Male gametangium

Pythiales

• terrestrial, plant pathogens or aquatic saprotrophs

• sterol auxotrophs

• Phytopthora, Pythium

• Phytopthora infestans-Irish Potato Famine

Sterol auxotroph

Take sterols from the host

Peronosporales

• downy mildew

• obligate biotrophs- haustoria

• Decidious sporangia

• Development of bourdeaux

Decidious sporangia

Sporangiophares leave the sporangia structure