Eukaryotic Microbes: Algae and Protozoa

• Chapter 5 focuses on eukaryotic microbes, specifically algae, protozoa, and fungi.

Algae

• Photosynthetic eukaryotic microorganisms.
• All algal cells contain cytoplasm, a cell wall (usually), a cell membrane, a nucleus, plastids, ribosomes, mitochondria, and Golgi bodies.
• Some algae possess a pellicle, stigma, and/or flagella.
• Algae produce 70% of the oxygen in the atmosphere.
• Common pond water algae include Euglena sp. and Volvox sp.

Prototheca

• A genus of algae that can cause human infections, leading to protothecosis.

Dinoflagellates

• Can produce phycotoxins that lead to paralytic shellfish poisoning.

Protozoa

• Unicellular, non-photosynthetic eukaryotes, most of which are free-living.
• Trophozoite is the motile, feeding, dividing stage.
• Cyst is the nonmotile, dormant, survival stage.
• Common pond water protozoa include Amoeba sp., Stentor sp., Vorticella sp., and Paramecium sp..

Amoebae

• Use pseudopodia (false feet) for locomotion and feeding.
• Entamoeba histolytica causes amebic dysentery.

Ciliates

• These organisms move by means of hairlike cilia.
• Balantidium coli causes balantidiasis.

Flagellates

• Move using whiplike flagella.
• Giardia intestinalis causes giardiasis.

Sporozoa

• Have no visible means of locomotion.
• Plasmodium spp. causes malaria.

Fungi

• molds and mushrooms consist of multicellular fibers called hyphae
• yeasts grow as a single-celled organism
• Mushroom's or Toadstools are spore-bearing fruiting bodies of Fungi
• Mycelium is the body or vegetative structure of a fungus.
• Hyphae (filaments) form mycelium.
• Coenocytic, or aseptate hyphae, do not contain septa.
• Septate hyphae have cross walls called septa.

Fungal Reproduction

• Arthroconidia (arthrospores) form when hyphae fragment.
• Sporangiospores develop within a sporangium sac at a hyphal tip.
• Conidiospores are spores that are not enclosed in a sac but produced at the tips or sides of the hypha.
• Blastospores are produced from a vegetative mother cell budding.

Fungal Classification

• Chytridiomycota and Zygomycetous are groups of zoosporic fungi
• Chytridiomycota and Mucoromycota are fungal groups
• Glomeromycotina, Ascomycota, and Basidiomycota compromise the Dikarya group

Microsporidia

• A phylum of endoparasitic fungi that must infect host cells to complete their life cycle.
• Characterized by a polar tube for host invasion and can cause diarrhea.

Fungi: Moulds

• The vegetative hypha is the portion of a hypha that obtains nutrients.
• The aerial hypha is the portion concerned with reproduction.
• Mold is a multicellular mass.

Fungi: Fleshy Fungi

• Consist of a network of filaments or strands (the mycelium) that grows in soil or on rotting logs.
• These fungi include mushrooms, toadstools, puffballs, and bracket fungi.

Fungi: Medical Significance

• Yeasts are round to oval-shaped, lack mycelia, and reproduce asexually via budding.
• Saccharomyces cerevisiae is a yeast used in baking.
• Candida albicans is the yeast most frequently isolated from human clinical specimens.

Dimorphic Fungi

• Can live as either yeasts or molds, depending on growth conditions, a phenomenon known as dimorphism.

Fungal diseases

• Systemic mycoses affect deep within the body
• Subcutaneous mycoses occur beneath the skin
• Cutaneous mycoses affect hair, skin, and nails
• Superficial mycoses are localized, (e.g., hair shafts).
• Opportunistic mycoses are fungi harmless in their normal habitat but pathogenic in a compromised host.

Candidiasis

• Candida is a yeast (a type of fungus) commonly found on the skin and in the body, including the mouth, throat, gut, and vagina.