OomycetesCN. 07, 15, 12, 13, 05,

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Introduction

IntroductionWhat are oomycetes?• Oomycetes, a.k.a water molds, are fungus-

like protists, that feed on decaying organic material by absorbing nutrients through their cell walls, which are made of cellulose.

• “Oomycetes” came from the Greek words “oion”, which means “egg”, and “mukes”, meaning “fungus”. Therefore, “oomycetes” means “egg fungi”.

About Oomycetes

Characteristics

Anatomy and Functions• Their cell walls are composed of cellulose.

Its main purpose is to absorb food from its surroundings.

• Most oomycetes produce self-moving spores, which are called as zoospores. These spores swim through water in search for food. They also have two(2) flagella. These flagella have different structures and functions.

Characteristics

Anatomy and Functions• Oomycetes have tubular mitochondrial

cristae(Cristae are the internal “rooms” formed by the inner membrane of a mitochondrion).

• Filamentous, coenocytic, sometimes unicellular.

Characteristics

Habitat• Although they (oomycetes) are commonly

known for their other name, “water molds”, not all of them live near bodies of water. Most of them are terrestrial.

Characteristics

Reproduction• Diploid life cycle.I. Sexual Reproduction

– Oogonium (Female Gametophytes)– Antheridium (Male Gametophytes)– Spores: biflagellate zoospores

II. Asexual Reproduction– Spores: oospores

Life Cycle

oosphere (2n)

hypha

mycelium (2n)

Antheridium; produces

fertilization tubes (n)

Oogonium; containing

oospores (n)

zoospores

sporangium (2n)

Life Cycle

Life Cycle of Saprolegnia Sp.

Water Molds vs. Fungi

Water Molds vs. Fungi• Water molds have cellulose for their cell

walls, while fungi have chitin.• Water molds have diploid nuclei, whereas

fungi have haploid nuclei.• Self-motile spores of oomycetes usually

have two(2) flagella, while fungal spores have only one(1).

• They both have different metabolic pathways for synthesizing lysine(an essential amino acid).

• Number of certain enzymes differ.

Impacts

Impacts

On Animals• Some water molds are parasites to some

animals. They can grow on scales/eggs of some fishes/amphibians. One good example is the water mold Saprolegnia. They are parasitic to organisms such as rotifers, nematodes, arthropods, and diatoms.

ImpactsOn Plants• Some water molds affect plants, too, such

as root-rotting fungi, seedling-dampening mold, blister rusts, white rusts (Albugo), and downy mildews. They invade plants like grapes, lettuces, corns, cabbages, and many other crop plants.

• Two water molds have had a major impact on world history: Phytophthora infestans, which causes Late Blight of Potato, and; Plasmopara viticola, which are the downy mildews of grapes.

ImpactsOn Humans• The two water molds mentioned earlier,

Phytophthora infestans and Plasmopara viticola, affected many crops (potatoes, grapes, etc.), it also affected people and some of their jobs in those early times.

• The Great Potato Famine, is one of the greatest problems that these water molds gave us.

Gallery

Gallery

Reproductive Structures of Phytophthora infestans

Gallery

Sporangium of Phytophthora infestans

Gallery

A water mold from a stream

Gallery

Saprolegnia sp.

Links

• http://encarta.msn.com/dictionary_561534904/oomycete.html;• http://www.ucmp.berkeley.edu/chromista/oomycota.html;• http://en.wikipedia.org/wiki/File:Phytophtora_reproduction.png;• http://en.wikipedia.org/wiki/Oomycetes;• http://www.aber.ac.uk/fungi/fungi/taxonomy.htm;• http://kentsimmons.uwinnipeg.ca/16cm05/16labman05/lb2pg2.htm